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diff --git a/20871.txt b/20871.txt new file mode 100644 index 0000000..511aa31 --- /dev/null +++ b/20871.txt @@ -0,0 +1,10769 @@ +The Project Gutenberg eBook, Human Foods and Their Nutritive Value, by +Harry Snyder + + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + + + + +Title: Human Foods and Their Nutritive Value + + +Author: Harry Snyder + + + +Release Date: March 22, 2007 [eBook #20871] + +Language: English + +Character set encoding: ISO-646-US (US-ASCII) + + +***START OF THE PROJECT GUTENBERG EBOOK HUMAN FOODS AND THEIR NUTRITIVE +VALUE*** + + +E-text prepared by Juliet Sutherland, Janet Blenkinship, and the Project +Gutenberg Online Distributed Proofreading Team (https://www.pgdp.net) + + + +Note: Project Gutenberg also has an HTML version of this + file which includes the original illustrations. + See 20871-h.htm or 20871-h.zip: + (https://www.gutenberg.org/dirs/2/0/8/7/20871/20871-h/20871-h.htm) + or + (https://www.gutenberg.org/dirs/2/0/8/7/20871/20871-h.zip) + + +Transcribers note: + + In this text, subscripted numbers are represented thus: _{12} + + + + + +HUMAN FOODS AND THEIR NUTRITIVE VALUE + +by + +HARRY SNYDER, B.S. + + + + + + + +New York +The MacMillan Company +1914 +All rights reserved +Copyright, 1908, +by the MacMillan Company. + +Set up and electrotyped. Published November, 1908. Reprinted +October, 1909; September, 1910; February, 1911; September, 1912; +May, December, 1913; June, 1914. + +Norwood Press +J. S. Cushing Co.--Berwick & Smith Co. +Norwood, Mass., U.S.A. + + + + + +PREFACE + + +Since 1897 instruction has been given at the University of Minnesota, +College of Agriculture, on human foods and their nutritive value. With +the development of the work, need has been felt for a text-book +presenting in concise form the composition and physical properties of +foods, and discussing some of the main factors which affect their +nutritive value. To meet the need, this book has been prepared, +primarily for the author's classroom. It aims to present some of the +principles of human nutrition along with a study of the more common +articles of food. It is believed that a better understanding of the +subject of nutrition will suggest ways in which foods may be selected +and utilized more intelligently, resulting not only in pecuniary saving, +but also in greater efficiency of physical and mental effort. + +Prominence is given in this work to those foods, as flour, bread, +cereals, vegetables, meats, milk, dairy products, and fruits, that are +most extensively used in the dietary, and to some of the physical, +chemical, and bacteriological changes affecting digestibility and +nutritive value which take place during their preparation for the table. +Dietary studies, comparative cost and value of foods, rational feeding +of men, and experiments and laboratory practice form features of the +work. Some closely related topics, largely of a sanitary nature, as the +effect upon food of household sanitation and storage, are also briefly +discussed. References are given in case more extended information is +desired on some of the subjects treated. While this book was prepared +mainly for students who have taken a course in general chemistry, it has +been the intention to present the topics in such a way as to be +understood by the layman also. + +This work completes a series of text-books undertaken by the author +over ten years ago, dealing with agricultural and industrial subjects: +"Chemistry of Plant and Animal Life," "Dairy Chemistry," "Soils and +Fertilizers," and "Human Foods and their Nutritive Value." It has been +the aim in preparing these books to avoid as far as possible repetition, +but at the same time to make each work sufficiently complete to permit +its use as a text independent of the series. + +One of the greatest uses that science can serve is in its application to +the household and the everyday affairs of life. Too little attention is +generally bestowed upon the study of foods in schools and colleges, and +the author sincerely hopes the time will soon come when more prominence +will be given to this subject, which is the oldest, most important, most +neglected, and least understood of any that have a direct bearing upon +the welfare of man. + + HARRY SNYDER. + + + + + CONTENTS + + + CHAPTER I + PAGE + GENERAL COMPOSITION OF FOODS 1 + + Water; Dry Matter; Variations in Weight of Foods; + Ash; Function of Ash in Plant Life; Organic Matter; + Products of Combustion of Organic Matter; Classification + of Organic Compounds; Non-nitrogenous Compounds; + Carbohydrates; Cellulose; Amount of Cellulose in Foods; + Crude Fiber; Starch; Microscopic Structure of Starch; + Dextrin; Food Value of Starch; Sugar; Pectose Substances; + Nitrogen-free-extract; Fats; Fuel Value of Fats; + Iodine Number of Fats; Glycerol Content of Fats; Ether + Extract and Crude Fat; Organic Acids; Dietetic Value + of Organic Acids; Essential Oils; Mixed Compounds; + Nutritive Value of Non-nitrogenous Compounds; Nitrogenous + Compounds; General Composition; Protein; Sub-divisions + of Proteins; Crude Protein; Food Value of + Protein; Albuminoids; Amids and Amines; Alkaloids; + General Relationship of the Nitrogenous Compounds. + + + CHAPTER II + + CHANGES IN COMPOSITION OF FOODS DURING COOKING AND + PREPARATION 27 + + Raw and Cooked Foods compared as to Composition; + Chemical Changes during Cooking; General Changes + affecting Cellulose, Starch, Sugar, Pectin Bodies, Fats, + Proteids; Effect of Chemical Changes on Digestibility; + Physical Changes during Cooking; Action of Heat on + Animal and Plant Tissues; Amount of Heat required for + Cooking; Bacteriological Changes; Insoluble Ferments; + Soluble Ferments; Bacterial Action Necessary in Preparation + of Some Foods; Injurious Bacterial Action; General + Relationship of Chemical, Physical, and Bacteriological + Changes; Esthetic Value of Foods; Color of Foods; + Natural and Artificial Colors; Conditions under which + Use of Chemicals in Preparation of Foods is Justifiable. + + + CHAPTER III + + VEGETABLE FOODS 37 + + General Composition; Potatoes; Chemical and Mechanical + Composition; Uses of Potatoes in Dietary; Sweet + Potatoes; Carrots; Parsnips; Cabbage; Cauliflower; + Beets; Cucumbers; Lettuce; Onions; Spinach; Asparagus; + Melons; Tomatoes; Sweet Corn; Eggplant; + Squash; Celery; Dietetic Value of Vegetables; Nutrient + Content of Vegetables; Sanitary Condition of Vegetables; + Miscellaneous Compounds in Vegetables; Canned Vegetables; + Edible Portion and Refuse of Vegetables. + + + CHAPTER IV + + FRUITS, FLAVORS AND EXTRACTS 48 + + General Composition; Food Value; Apples; Oranges; + Lemons; Grape Fruit; Strawberries; Grapes; Peaches; + Plums; Olives; Figs; Dried Fruits; Uses of Fruit in + the Dietary; Canning and Preservation of Fruits; Adulterated + Canned Fruits; Fruit Flavors and Extracts; Synthetic + Preparation of Flavors. + + + CHAPTER V + + SUGARS, MOLASSES, SYRUP, HONEY, AND CONFECTIONS 58 + + Composition of Sugars; Beet Sugar; Cane Sugar; + Manufacture of Sugar; Sulphur Dioxid and Indigo, Uses + of, in Sugar Manufacture; Commercial Grades of Sugar; + Sugar in the Dietary; Maple Sugar; Adulteration of + Sugar; Dextrose Sugars; Inversion of Sugars; Molasses; + Syrups; Adulteration of Molasses; Sorghum Syrup; + Maple Syrup; Analysis of Sugar; Adulteration of Syrups; + Honey; Confections; Coloring Matter in Candies; Coal + Tar Dyes; Saccharine. + + + CHAPTER VI + + LEGUMES AND NUTS 71 + + General Composition of Legumes; Beans; Digestibility + of Beans; Use of Beans in the Dietary; String + Beans; Peas; Canned Peas; Peanuts; General Composition + of Nuts; Chestnuts; The Hickory Nut; Almonds; + Pistachio; Cocoanuts; Uses of Nuts in the Dietary. + + + CHAPTER VII + + MILK AND DAIRY PRODUCTS 80 + + Importance in the Dietary; General Composition; Digestibility; + Sanitary Condition of Milk; Certified Milk; + Pasteurized Milk; Tyrotoxicon; Color of Milk; Souring + of Milk; Use of Preservatives in Milk; Condensed Milk; + Skim Milk; Cream; Buttermilk; Goat's Milk; Koumiss; + Prepared Milks; Human Milk; Adulteration of Milk; + Composition of Butter; Digestibility of Butter; Adulteration + of Butter; General Composition of Cheese; + Digestibility; Use in the Dietary; Cottage Cheese; Different + Kinds of Cheese; Adulteration of Cheese; Dairy + Products in the Dietary. + + + CHAPTER VIII + + MEATS AND ANIMAL FOOD PRODUCTS 98 + + General Composition; Mineral Matter; Fat; Protein; + Non-nitrogenous Compounds; Why Meats vary in Composition; + Amides; Albuminoids; Taste and Flavor of + Meats; Alkaloidal Bodies in Meats; Ripening of Meats + in Cold Storage; Beef; Veal; Mutton; Pork; Lard; + Texture and Toughness of Meat; Influence of Cooking + upon the Composition of Meats; Beef Extracts; Miscellaneous + Meat Products; Pickled Meats; Saltpeter in + Meats; Smoked Meats; Poultry; Fish; Oysters, Fattening + of; Shell Fish; Eggs, General Composition; Digestibility + of Eggs; Use of Eggs in the Dietary; Canned + Meats, General Composition. + + + CHAPTER IX + + CEREALS 121 + + Preparation and Cost of Cereals; Various Grains used + in making Cereal Products; Cleanliness of; Corn Preparations; + Corn Flour; Use of Corn in Dietary; Corn Bread; + Oat Preparations; Cooking of Oatmeal; Wheat Preparations; + Flour Middlings; Breakfast Foods; Digestibility + of Wheat Preparations; Barley Preparations; Rice Preparations; + Predigested Foods; The Value of Cereals in the + Dietary; Phosphate Content of Cereals; Phosphorus Requirements + of a Ration; Mechanical Action of Cereals + upon Digestion; Cost and Nutritive Value of Cereals. + + + CHAPTER X + + WHEAT FLOUR 133 + + Use for Bread Making; Winter and Spring Wheat + Flours; Composition of Wheat and Flour; Roller Process + of Flour Milling; Grades of Flour; Types of Flour; Composition + of Flour; Graham and Entire Wheat Flours; + Composition of Wheat Offals; Aging and Curing of Flour; + Macaroni Flour; Color; Granulation; Capacity of Flour + to absorb Water; Physical Properties of Gluten; Gluten + as a Factor in Bread Making; Unsoundness; Comparative + Baking Tests; Bleaching; Adulteration of Flour; Nutritive + Value of Flour. + + + CHAPTER XI + + BREAD AND BREAD MAKING 158 + + Leavened and Unleavened Bread; Changes during + Bread Making; Loss of Dry Matter during Bread Making; + Action of Yeast; Compressed Yeast; Dry Yeast; Production + of Carbon Dioxid Gas and Alcohol; Production + of Soluble Carbohydrates; Production of Acids in Bread + Making; Volatile Compounds produced during Bread + Making; Behavior of Wheat Proteids in Bread Making; + Production of Volatile Nitrogenous Compounds; Oxidation + of Fat; Influence of the Addition of Wheat Starch + and Gluten to Flour; Composition of Bread; Use of + Skim Milk and Lard in Bread Making; Influence of + Warm and Cold Flours in Bread Making; Variations in + the Process of Bread Making; Digestibility of Bread; + Use of Graham and Entire Wheat in the Dietary; Mineral + Content of White Bread; Comparative Digestibility + of New and Old Bread; Different Kinds of Bread; Toast. + + + CHAPTER XII + + BAKING POWDERS 186 + + General Composition; Cream of Tartar Powders; Residue + from Cream of Tartar Baking Powders; Tartaric + Acid Powders; Phosphate Baking Powders; Mineral and + Organic Phosphates; Phosphate Residue; Alum Baking + Powders; Residue from Alum Baking Powders; Objections + urged against Alum Powders; Action of Baking + Powders and Yeast Compared; Keeping Qualities of + Baking Powders; Inspection of Baking Powders; Fillers; + Home-made Baking Powders. + + + CHAPTER XIII + + VINEGAR, SPICES, AND CONDIMENTS 193 + + Vinegar; Chemical Changes during Manufacture of + Vinegar; Ferment Action; Materials used in Preparation + of Vinegars; Characteristics of a Good Vinegar; Vinegar + Solids; Acidity of Vinegar; Different Kinds of Vinegars; + Standards of Purity; Adulteration of Vinegar; Characteristics + of Spices; Pepper; Cayenne; Mustard; Ginger; + Cinnamon and Cassia; Cloves; Allspice; Nutmeg; Adulteration + of Spices and Condiments; Essential Oils of; + Uses of Condiments in Preparation of Foods; Action of + Condiments upon Digestion; Condiments and Natural + Flavors. + + + CHAPTER XIV + + TEA, COFFEE, CHOCOLATE, AND COCOA 203 + + Tea; Sources of Tea Supply; Composition of Tea; + Black Tea and Green Tea; Judging Teas; Adulteration + of Tea; Food Value and Physiological Properties of Tea; + Composition of Coffee; Adulteration of Coffee; Chicory + in Coffee; Glazing of Coffee; Cereal Coffee Substitutes; + Cocoa and Chocolate Preparations; Composition of Cocoa; + Chocolate; Cocoa Nibs; Plain Chocolate; Sweet Chocolate; + Cocoa Butter; Nutritive Value of Cocoa; Adulteration + of Chocolate and Cocoa; Comparative Composition + of Beverages. + + + CHAPTER XV + + THE DIGESTIBILITY OF FOOD 214 + + Digestibility, how Determined; Completeness and Ease + of Digestion Process; Example of Digestion Experiment; + Available Nutrients; Available Energy; Caloric Value of + Foods; Normal Digestion and Health; Digestibility of + Animal Foods; Digestibility of Vegetable Foods; Factors + influencing Digestion; Combination of Foods; Amount + of Food; Method of Preparation of Food; Mechanical + Condition of Foods; Mastication; Palatability of Foods; + Physiological Properties of Foods; Individuality; Psychological + Factors. + + + CHAPTER XVI + + COMPARATIVE COST AND VALUE OF FOODS 231 + + Cost and Nutrient Content of Foods; How to compare + Two Foods as to Nutritive Value; Cheap Foods; Expensive + Foods; Nutrients Procurable for a Given Sum; Examples; + Comparing Nutritive Value of Common Foods + at Different Prices; Cost and Value of Nutrients. + + + CHAPTER XVII + + DIETARY STUDIES 244 + + Object of Dietary Studies; Wide and Narrow Rations; + Dietary Standards; Number of Meals per Day; Mixed + Dietary Desirable; Animal and Vegetable Foods; + Economy of Production; Food Habits; Underfed Families; + Cheap and Expensive Foods; Food Notions; + Dietary of Two Families Compared; Food in its Relation + to Mental and Physical Vigor; Dietary Studies in Public + Institutions. + + + CHAPTER XVIII + + RATIONAL FEELING OF MAN 261 + + Object; Human and Animal Feeding Compared; Standard + Rations; Why Tentative Dietary Standards; Amounts + of Food Consumed; Average Composition of Foods; + Variations in Composition of Foods; Example of a Ration; + Calculations of Balanced Rations; Requisites of a + Balanced Ration; Examples; Calculations of Rations for + Men at Different Kinds of Labor. + + + CHAPTER XIX + + WATER 268 + + Importance; Impurities in Water; Mineral Impurities; + Organic Impurities; Interpretation of a Water Analysis; + Natural Purification of Water; Water in Relation to + Health; Improvement of Waters; Boiling of Water; Filtration; + Purification of Water by Addition of Chemicals; + Ice; Rain Waters; Waters of High and Low Purity; + Chemical Changes which Organic Matter of Water Undergoes; + Bacterial Content of Water; Mineral Waters; + Materials for Softening Water; Uses of; Economic Value + of a Pure Water Supply. + + + CHAPTER XX + + FOOD AS AFFECTED BY HOUSEHOLD SANITATION AND + STORAGE 284 + + Injurious Compounds in Foods; Nutrient Content and + Sanitary Condition of Food; Sources of Contamination + of Food; Unclean Ways of Handling Food; Sanitary Inspection + of Food; Infection from Impure Air; Storage + of Food in Cellars; Respiration of Vegetable Cells; Sunlight, + Pure Water, and Pure Air as Disinfectants; Foods + contaminated from Leaky Plumbing; Utensils for Storage + of Food; Contamination from Unclean Dishcloths; Refrigeration; + Chemical Changes that take Place in the + Refrigerator; Soil; Disposal of Kitchen Refuse; Germ + Diseases spread by Unsanitary Conditions around Dwellings + due to Contamination of Food; General Considerations; + Relation of Food to Health. + + + CHAPTER XXI + + LABORATORY PRACTICE 299 + + Object of Laboratory Practice; Laboratory Note-book + and Suggestions for Laboratory Practice; List of Apparatus + Used; Photograph of Apparatus Used; Directions + for Weighing; Directions for Measuring; Use of Microscope; + Water in Flour; Water in Butter; Ash in Flour; + Nitric Acid Test for Nitrogenous Organic Matter; Acidity + of Lemons; Influence of Heat on Potato Starch Grains; + Influence of Yeast on Starch Grains; Mechanical Composition + of Potatoes; Pectose from Apples; Lemon Extract; + Vanilla Extract; Testing Olive Oil for Cotton Seed Oil; + Testing for Coal Tar Dyes; Determining the Per Cent of + Skin in Beans; Extraction of Fat from Peanuts; Microscopic + Examination of Milk; Formaldehyde in Cream or + Milk; Gelatine in Cream or Milk; Testing for Oleomargarine; + Testing for Watering or Skimming of Milk; Boric + Acid in Meat; Microscopic Examination of Cereal Starch + Grains; Identification of Commercial Cereals; Granulation + and Color of Flour; Capacity of Flour to absorb + Water; Acidity of Flour; Moist and Dry Gluten; Gliadin + from Flour; Bread-making Test; Microscopic Examination + of Yeast; Testing Baking Powders for Alum; Testing + Baking Powders for Phosphoric Acid; Testing Baking + Powders for Ammonia; Vinegar Solids; Specific Gravity + of Vinegar; Acidity of Vinegar; Deportment of Vinegar + with Reagents; Testing Mustard for Turmeric; Examination + of Tea Leaves; Action of Iron Compounds upon + Tannic Acid; Identification of Coffee Berries; Detecting + Chicory in Coffee; Comparative Amounts of Soap Necessary + with Hard and Soft Water; Solvent Action of Water + on Lead; Suspended Matter in Water; Organic Matter + in Water; Deposition of Lime by Boiling Water; Qualitative + Tests for Minerals in Water; Testing for Nitrites + in Water. + + REVIEW QUESTIONS 323 + + REFERENCES 350 + + INDEX 357 + + + + +HUMAN FOODS AND THEIR NUTRITIVE VALUE + + + + +CHAPTER I + +GENERAL COMPOSITION OF FOODS + + +1. Water.--All foods contain water. Vegetables in their natural +condition contain large amounts, often 95 per cent, while in meats there +is from 40 to 60 per cent or more. Prepared cereal products, as flour, +corn meal, and oatmeal, which are apparently dry, have from 7 to 14 per +cent. In general the amount of water in a food varies with the +mechanical structure and the conditions under which it has been +prepared, and is an important factor in estimating the value, as the +nutrients are often greatly decreased because of large amounts of water. +The water in substances as flour and meal is mechanically held in +combination with the fine particles and varies with the moisture +content, or hydroscopicity, of the air. Oftentimes foods gain or lose +water to such an extent as to affect their weight; for example, one +hundred pounds of flour containing 12 per cent of water may be reduced +in weight three pounds or more when stored in a dry place, or there may +be an increase in weight from being stored in a damp place. In tables +of analyses the results, unless otherwise stated, are usually given on +the basis of the original material, or the dry substance. Potatoes, for +example, contain 2-1/2 per cent of crude protein on the basis of 75 per +cent of water; or on a dry matter basis, that is, when the water is +entirely eliminated, there is 10 per cent of protein. + +The water of foods is determined by drying the weighed material in a +water or air oven at a temperature of about 100 deg. C, until all of the +moisture has been expelled in the form of steam, leaving the dry matter +or material free from water.[1] The determination of dry matter, while +theoretically a simple process, is attended with many difficulties. +Substances which contain much fat may undergo oxidation during drying; +volatile compounds, as essential oils, are expelled along with the +moisture; and other changes may occur affecting the accuracy of the +work. The last traces of moisture are removed with difficulty from a +substance, being mechanically retained by the particles with great +tenacity. When very accurate dry matter determinations are desired, the +substance is dried in a vacuum oven, or in a desiccator over sulphuric +acid, or in an atmosphere of some non-oxidizing gas, as hydrogen. + + +2. Dry Matter.--The dry matter of a food is a mechanical mixture of +the various compounds, as starch, sugar, fat, protein, cellulose, and +mineral matter, and is obtained by drying the material. Succulent +vegetable foods with 95 per cent of water contain only 5 per cent of +dry matter, while in flour with 12 per cent of water there is 88 per +cent, and in sugar 99 per cent. The dry matter is obtained by +subtracting the per cent of water from 100, and in foods it varies from +5 per cent and less in some vegetables to 99 per cent in sugar. + +[Illustration: FIG. 1.--APPARATUS USED FOR THE DETERMINATION OF DRY +MATTER AND ASH IN FOODS. + +1, desiccator; 2, muffle furnace for combustion of foods and obtaining +ash; 3, water oven for drying food materials.] + + +3. Ash.--The ash, or mineral matter, is that portion obtained by +burning or igniting the dry matter at the lowest temperature necessary +for complete combustion. The ash in vegetable foods ranges from 2 to 5 +per cent and, together with the nitrogen, represents what was taken from +the soil during growth. In animal bodies, the ash is present mainly in +the bones, but there is also an appreciable amount, one per cent or +more, in all the tissues. Ash is exceedingly variable in composition, +being composed of the various salts of potassium, sodium, calcium, +magnesium, and iron, as sulphates, phosphates, chlorides, and silicates +of these elements. There are also other elements in small amounts. In +the plant economy these elements take an essential part and are +requisite for the formation of plant tissue and the production in the +leaves of the organic compounds which later are stored up in the seeds. +Some of the elements appear to be more necessary than others, and +whenever withheld plant growth is restricted. The elements most +essential for plant growth are potassium, calcium, magnesium, iron, +phosphorus, and sulphur.[1] + +In the animal body minerals are derived, either directly or indirectly, +from the vegetable foods consumed. The part which each of the mineral +elements takes in animal nutrition is not well understood. Some of the +elements, as phosphorus and sulphur, are in organic combination with the +nitrogenous compounds, as the nucleated albuminoids, which are very +essential for animal life. In both plant and animal bodies, the mineral +matter is present as mineral salts and organic combinations. It is held +that the ash elements which are in organic combination are the forms +mainly utilized for tissue construction. While it is not known just what +part all the mineral elements take in animal nutrition, experiments show +that in all ordinary mixed rations the amount of the different mineral +elements is in excess of the demands of the body, and it is only in rare +instances, as in cases of restricted diet, or convalescence from some +disease, that special attention need be given to increasing the mineral +content of the ration. An excess of mineral matter in foods is equally +as objectionable as a scant amount, elimination of the excess entailing +additional work on the body. + +The composition of the ash of different food materials varies widely, +both in amount, and form of the individual elements. When for any reason +it is necessary to increase the phosphates in a ration, milk and eggs do +this to a greater extent than almost any other foods. Common salt, or +sodium chloride, is one of the most essential of the mineral +constituents of the body. It is necessary for giving the blood its +normal composition, furnishing acid and basic constituents for the +production of the digestive fluids, and for the nutrition of the cells. +While salt is a necessary food, in large amounts, as when the attempt is +made to use sea water as a beverage, it acts as a poison, suggesting +that a material may be both a food and a poison. When sodium chloride is +entirely withheld from an animal, death from salt starvation ensues. +Many foods contain naturally small amounts of sodium chloride. + + +4. Organic Matter.--That portion of a food material which is converted +into gaseous or volatile products during combustion is called the +organic matter. It is a mechanical mixture of compounds made up of +carbon, hydrogen, oxygen, nitrogen, and sulphur, and is composed of +various individual organic compounds, as cellulose, starch, sugar, +albumin, and fat. The amount in a food is determined by subtracting the +ash and water from 100. The organic matter varies widely in composition; +in some foods it is largely starch, as in potatoes and rice, while in +others, as forage crops consumed by animals, cellulose predominates. The +nature of the prevailing organic compound, as sugar or starch, +determines the nutritive value of a food. Each has a definite chemical +composition capable of being expressed by a formula. Considered +collectively, the organic compounds are termed organic matter. When +burned, the organic compounds are converted into gases, the carbon +uniting with the oxygen of the air to form carbon dioxide, hydrogen to +form water, sulphur to form sulphur dioxide, and the nitrogen to form +oxides of nitrogen and ammonia. + + +5. Classification of Organic Compounds.--All food materials are +composed of a large number of organic compounds. For purposes of study +these are divided into classes. The element nitrogen is taken as the +basis of the division. Compounds which contain this element are called +nitrogenous, while those from which it is absent are called +non-nitrogenous.[2] The nitrogenous organic compounds are composed of +the elements nitrogen, hydrogen, carbon, oxygen, and sulphur, while the +non-nitrogenous compounds are composed of carbon, hydrogen, and oxygen. +In vegetable foods the non-nitrogenous compounds predominate, there +being usually from six to twelve parts of non-nitrogenous to every one +part of nitrogenous, while in animal foods the nitrogenous compounds are +present in larger amount. + + +NON-NITROGENOUS COMPOUNDS + +6. Occurrence.--The non-nitrogenous compounds of foods consist mainly +of cellulose, starch, sugar, and fat. For purposes of study, they are +divided into subdivisions, as carbohydrates, pectose substances or +jellies, fats, organic acids, essential oils, and mixed compounds. In +plants the carbohydrates predominate, while in animal tissue the fats +are the chief non-nitrogenous constituents. + + +7. Carbohydrates.--This term is applied to a class of compounds +similar in general composition, but differing widely in structural +composition and physical properties. Carbohydrates make up the bulk of +vegetable foods and, except in milk, are found only in traces in animal +foods. They are all represented by the general formula CH_2n_2n, there +being twice as many hydrogen as oxygen atoms, the hydrogen and oxygen +being present in the same proportion as in water. As a class, the +carbohydrates are neutral bodies, and, when burned, form carbon dioxide +and water. + +[Illustration: FIG. 2.--CELLULAR STRUCTURE OF PLANT CELL.] + +8. Cellulose is the basis of the cell structure of plants, and is +found in various physical forms in food materials.[3] Sometimes it is +hard and dense, resisting digestive action and mechanically inclosing +other nutrients and thus preventing their being available as food. In +the earlier stages of plant growth a part of the cellulose is in +chemical combination with water, forming hydrated cellulose, a portion +of which undergoes digestion and produces heat and energy in the body. +Ordinarily, however, cellulose adds but little in the way of nutritive +value, although it is often beneficial mechanically and imparts bulk to +some foods otherwise too concentrated. The mechanical action of +cellulose on the digestion of food is discussed in Chapter XV. +Cellulose usually makes up a very small part of human food, less than 1 +per cent. In refined white flour there is less than .05 of a per cent; +in oatmeal and cereal products from .5 to 1 per cent, depending upon the +extent to which the hulls are removed, and in vegetable foods from .1 to +1 per cent. The cellulose content of foods is included in the crude +fiber of the chemist's report. + +9. Starch occurs widely distributed in nature, particularly in the +seeds, roots, and tubers of some plants. It is formed in the leaves of +plants as a result of the joint action of chlorophyll and protoplasm, +and is generally held by plant physiologists to be the first +carbohydrate produced in the plant cell. Starch is composed of a number +of overlapping layers separated by starch cellulose; between these +layers the true starch or amylose is found. Starch from the various +cereals and vegetables differs widely in mechanical structure; in wheat +it is circular, in corn somewhat angular, and in parsnips exceedingly +small, while potato starch granules are among the largest.[4] The nature +of starch can be determined largely from its mechanical structure as +studied under the microscope. It is insoluble in cold water because of +the protecting action of the cellular layer, but on being heated it +undergoes both mechanical and chemical changes; the grains are partially +ruptured by pressure due to the conversion into steam of the moisture +held mechanically. The cooking of foods is beneficial from a mechanical +point of view, as it results in partial disintegration of the starch +masses, changing the structure so that the starch is more readily acted +upon by the ferments of the digestive tract. At a temperature of about +120 deg. C. starch begins to undergo chemical change, resulting in the +rearrangement of the atoms in the molecule with the production of +dextrine and soluble carbohydrates. Dextrine is formed on the crust of +bread, or whenever potatoes or starchy foods are browned. At a still +higher temperature starch is decomposed, with the liberation of water +and production of compounds of higher carbon content. When heated in +contact with water, it undergoes hydration changes; gelatinous-like +products are formed, which are finally converted into a soluble +condition. In cooking cereals, the hydration of the starch is one of the +main physical and chemical changes that takes place, and it simply +results in converting the material into such a form that other chemical +changes may more readily occur. Before starch becomes dextrose, +hydration is necessary. If this is accomplished by cooking, it saves the +body just so much energy in digestion. Many foods owe their value +largely to the starch. In cereals it is found to the extent of 72 to 76 +per cent; in rice and potatoes in still larger amounts; and it is the +chief constituent of many vegetables. When starch is digested, it is +first changed to a soluble form and then gradually undergoes oxidation, +resulting in the production of heat and energy, the same +products--carbon dioxide and water--being formed as when starch is +burned. Starch is a valuable heat-producing nutrient; a pound yields +1860 calories. See Chapter XV. + +10. Sugar.--Sugars are widely distributed in nature, being found +principally in the juices of the sugar cane, sugar beet, and sugar +maple. They are divided into two large classes: the sucrose group and +the dextrose group, the latter being produced from sucrose, starch, and +other carbohydrates by inversion and allied chemical changes. Because of +the importance of sugar in the dietary, Chapter V is devoted to the +subject. + +11. Pectose Substances are jelly-like bodies found in fruits and +vegetables. They are closely related in chemical composition to the +carbohydrates, into which form they are changed during digestion; and in +nutrition they serve practically the same function. In the early stages +of growth the pectin bodies are combined with organic acids, forming +insoluble compounds, as the pectin in green apples. During the ripening +of fruit and the cooking of vegetables, the pectin is changed to a more +soluble and digestible condition. In food analysis, the pectin is +usually included with the carbohydrates. + +12. Nitrogen-free-extract.--In discussing the composition of foods, +the carbohydrates other then cellulose, as starch, sugar, and pectin, +are grouped under the name of nitrogen-free-extract. Methods of +chemical analysis have not yet been sufficiently perfected to +enable accurate and rapid determination to be made of all these +individual carbohydrates, and hence they are grouped together as +nitrogen-free-extract. As the name indicates, they are compounds which +contain no nitrogen, and are extractives in the sense that they are +soluble in dilute acid and alkaline solutions. The nitrogen-free-extract +is determined indirectly, that is, by the method of difference. All the +other constituents of a food, as water, ash, crude fiber (cellulose), +crude protein, and ether extract, are determined; the total is +subtracted from 100, and the difference is nitrogen-free-extract. In +studying the nutritive value of foods, particular attention should be +given to the nature of the nitrogen-free-extract, as in some instances +it is composed of sugar and in others of starch, pectin, or pentosan +(gum sugars). While all these compounds have practically the same fuel +value, they differ in composition, structure, and the way in which they +are acted upon by chemicals and digestive ferments.[1] + +[Illustration: FIG. 3.--APPARATUS USED FOR THE DETERMINATION OF +FAT.] + +13. Fat.--Fat is found mainly in the seeds of plants, but to some +extent in the leaves and stems. It differs from starch in containing +more carbon and less oxygen. In starch there is about 44 per cent of +carbon, while in fat there is 75 per cent. Hence it is that when fat is +burned or undergoes combustion, it yields a larger amount of the +products of combustion--carbon dioxid and water--than does starch. A +gram of fat produces 2-1/4 times as much heat as a gram of starch. Fat +is the most concentrated non-nitrogenous nutrient. As found in food +materials, it is a mechanical mixture of various fats, among which are +stearin, palmitin, and olein. Stearin and palmitin are hard fats, +crystalline in structure, and with a high melting point, while olein is +a liquid. In addition to these three, there are also small amounts of +other fats, as butyrin in butter, which give character or individuality +to materials. There are a number of vegetable fats or oils which are +used for food purposes and, when properly prepared and refined, have a +high nutritive value. Occasionally one fat of cheaper origin but not +necessarily of lower nutritive value is substituted for another. The +fats have definite physical and chemical properties which enable them to +be readily distinguished, as iodine number, specific gravity, index of +refraction, and heat of combustion. By iodine number is meant the +percentage of iodine that will unite chemically with the fat. Wheat oil +has an iodine number of about 100, meaning that one pound of wheat oil +will unite chemically with one pound of iodine. Fats have a lower +specific gravity than water, usually ranging from .89 to .94, the +specific gravity of a fat being fairly constant. All fats can be +separated into glycerol and a fatty acid, glycerol or glycerine being +common constituents, while each fat yields its own characteristic acid, +as stearin, stearic acid; palmitin, palmitic acid; and olein, oleic +acid. The fats are soluble in ether, chloroform, and benzine. In the +chemical analysis of foods, they are separated with ether, and along +with the fat, variable amounts of other substances are extracted, these +extractive products usually being called "ether extract" or "crude +fat."[5] The ether extract of plant tissue contains in addition to fat +appreciable amounts of cellulose, gums, coloring, and other materials. +From cereal products the ether extract is largely fat, but in some +instances lecithin and other nitrogenous fatty substances are present, +while in animal food products, as milk and meat, the ether extract is +nearly pure fat. + +14. Organic Acids.--Many vegetable foods contain small amounts of +organic acids, as malic acid found in apples, citric in lemons, and +tartaric in grapes. These give characteristic taste to foods, but have +no direct nutritive value. They do not yield heat and energy as do +starch, fat, and protein; they are, however, useful for imparting flavor +and palatability, and it is believed they promote to some extent the +digestion of foods with which they are combined by encouraging the +secretion of the digestive fluids. Many fruits and vegetables owe their +dietetic value to the organic acids which they contain. In plants they +are usually in chemical combination with the minerals, forming compounds +as salts, or with the organic compounds, producing materials as acid +proteins. In the plant economy they take an essential part in promoting +growth and aiding the plant to secure by osmotic action its mineral food +from the soil. Organic acids are found to some extent in animal foods, +as the various lactic acids of meat and milk. They are also formed in +food materials as the result of ferment action. When seeds germinate, +small amounts of carbohydrates are converted into organic acids. In +general the organic acids are not to be considered as nutrients, but as +food adjuncts, increasing palatability and promoting digestion. + +15. Essential Oils.--Essential or volatile oils differ from fats, or +fixed oils, in chemical composition and physical properties.[6] The +essential oils are readily volatilized, leaving no permanent residue, +while the fixed fats are practically non-volatile. Various essential +oils are present in small amounts in nearly all vegetable food +materials, and the characteristic flavor of many fruits is due to them. +It is these compounds which are used for flavoring purposes, as +discussed in Chapter IV. The amount in a food material is very small, +usually only a few hundredths of a per cent. The essential oils have no +direct food value, but indirectly, like the organic acids, they assist +in promoting favorable digestive action, and are also valuable because +they impart a pleasant taste. Through poor methods of cooking and +preparation, the essential oils are readily lost from some foods. + +16. Mixed Compounds.--Food materials frequently contain +compounds which do not naturally fall into the five groups +mentioned,--carbohydrates, pectose substances, fats, organic acids, and +essential oils. The amount of such compounds is small, and they are +classed as miscellaneous or mixed non-nitrogenous compounds. Some of +them may impart a negative value to the food, and there are others which +have all the characteristics, as far as general composition is +concerned, of the non-nitrogenous compounds, but contain nitrogen, +although as a secondary rather than an essential constituent. + +17. Nutritive Value of Non-nitrogenous Compounds.--The non-nitrogenous +compounds, taken as a class, are incapable alone of sustaining life, +because they do not contain any nitrogen, and this is necessary for +producing proteid material in the animal body. They are valuable for +the production of heat and energy, and when associated with the +nitrogenous compounds, are capable of forming non-nitrogenous reserve +tissue. It is equally impossible to sustain life for any prolonged +period with the nitrogenous compounds alone. It is when these two +classes are properly blended and naturally united in food materials that +their main value is secured. For nutrition purposes they are mutually +related and dependent. Some food materials contain the nitrogenous and +non-nitrogenous compounds blended in such proportion as to enable one +food alone to practically sustain life, while in other cases it is +necessary, in order to secure the best results in the feeding of animals +and men, to combine different foods varying in their content of these +two classes of compounds.[7] + + +NITROGENOUS COMPOUNDS + +18. General Composition.--The nitrogenous compounds are more complex +in composition than the non-nitrogenous. They are composed of a larger +number of elements, united in different ways so as to form a much more +complex molecular structure. Foods contain numerous nitrogenous organic +compounds, which, for purposes of study, are divided into four +divisions,--proteids, albuminoids, amids, and alkaloids. In addition to +these, there are other nitrogenous compounds which do not naturally fall +into any one of the four divisions. + +[Illustration: FIG. 4.--APPARATUS USED FOR DETERMINING +TOTAL NITROGEN AND CRUDE PROTEIN IN FOODS. + +The material is digested in the flask (3) with sulphuric acid and the +organic nitrogen converted into ammonium sulphate, which is later +liberated and distilled at 1, and the ammonia neutralized with standard +acid (2).] + +Also in some foods there are small amounts of nitrogen in mineral forms, +as nitrates and nitrites. + +19. Protein.--The term "protein" is applied to a large class of +nitrogenous compounds resembling each other in general composition, but +differing widely in structural composition. As a class, the proteins +contain about 16 per cent of nitrogen, 52 per cent of carbon, from 6 to +7 per cent of hydrogen, 22 per cent of oxygen, and less than 2 per cent +of sulphur. These elements are combined in a great variety of ways, +forming various groups or radicals. In studying the protein molecule a +large number of derivative products have been observed, as amid +radicals, various hydrocarbons, fatty acids, and carbohydrate-like +bodies.[8] It would appear that in the chemical composition of the +proteins there are all the constituents, or simpler products, of the +non-nitrogenous compounds, and these are in chemical combination with +amid radicals and nitrogen in various forms. The nitrogen of many +proteids appears to be present in more than one form or radical. The +proteids take an important part in life processes. They are found more +extensively in animal than in plant bodies. The protoplasm of both the +plant and animal cell is composed mainly of protein. + +Proteids are divided into various subdivisions, as albumins, globulins, +albuminates, proteoses and peptones, and insoluble proteids. In plant +and animal foods a large amount of the protein is present as insoluble +proteids; that is, they are not dissolved by solvents, as water and +dilute salt solution. The albumins are soluble in water and coagulated +by heat at a temperature of 157 deg. to 161 deg. F. Whenever a food material is +soaked in water, the albumin is removed and can then be coagulated by +the action of heat, or of chemicals, as tannic acid, lead acetate, and +salts of mercury. The globulins are proteids extracted from food +materials by dilute salt solution after the removal of the albumins. +Globulins also are coagulated by heat and precipitated by chemicals. The +amount of globulins in vegetable foods is small. In animal foods myosin +in meat and vitellin, found in the yolk of the egg, and some of the +proteids of the blood, are examples of globulins. Albuminates are +casein-like proteids found in both animal and vegetable foods. They are +supposed to be proteins that are in feeble chemical combination with +acid and alkaline compounds, and they are sometimes called acid and +alkali proteids. Some are precipitated from their solutions by acids and +others by alkalies. Peas and beans contain quite large amounts of a +casein-like proteid called legumin. Proteoses and peptones are proteins +soluble in water, but not coagulated by heat. They are produced from +other proteids by ferment action during the digestion of food and the +germination of seeds, and are often due to the changes resulting from +the action of the natural ferments or enzymes inherent in the food +materials. As previously stated, the insoluble proteids are present in +far the largest amount of any of the nitrogenous materials of foods. +Lean meat and the gluten of wheat and other grains are examples of the +insoluble proteids. The various insoluble proteids from different food +materials each has its own composition and distinctive chemical and +physical properties, and from each a different class and percentage +amount of derivative products are obtained.[1] While in general it is +held that the various proteins have practically the same nutritive +value, it is possible that because differences in structural composition +and the products formed during digestion there may exist notable +differences in nutritive value. During digestion the insoluble proteids +undergo an extended series of chemical changes. They are partially +oxidized, and the nitrogenous portion of the molecule is eliminated +mainly in the form of amids, as urea. The insoluble proteins constitute +the main source of the nitrogenous food supply of both humans and +animals. + +20. Crude Protein.--In the analysis of foods, the term "crude protein" +is used to designate the total nitrogenous compounds considered +collectively; it is composed largely of protein, but also includes the +amids, alkaloids, and albuminoids. "Crude protein" and "total +nitrogenous compounds" are practically synonymous terms. The various +proteins all contain about 16 per cent of nitrogen; that is, one part of +nitrogen is equivalent to 6.25 parts of protein. In analyzing a food +material, the total organic nitrogen is determined and the amount +multiplied by 6.25 to obtain the crude protein. In some food materials, +as cereals, the crude protein is largely pure protein, while in others, +as potatoes, it is less than half pure protein, the larger portion being +amids and other compounds. In comparing the crude protein content of one +food with that of another, the nature of both proteids should be +considered and also the amounts of non-proteid constituents. The factor +6.25 for calculating the protein equivalent of foods is not strictly +applicable to all foods. For example, the proteids of wheat--gliadin and +glutenin--contain over 18 per cent of nitrogen, making the nitrogen +factor about 5.68 instead of 6.25. If wheat contains 2 per cent of +nitrogen, it is equivalent to 12.5 per cent of crude protein, using the +factor 6.25; or to 11.4, using the factor 5.7. The nitrogen content of +foods is absolute; the protein content is only relative.[9] + +21. Food Value of Protein.--Because of its complexity in composition, +protein is capable of being used by the body in a greater variety of +ways than starch, sugar, or fat. In addition to producing heat and +energy, protein serves the unique function of furnishing material for +the construction of new muscular tissue and the repair of that which is +worn out. It is distinctly a tissue-building nutrient. It also enters +into the composition of all the vital fluids of the body, as the blood, +chyme, chyle, and the various digestive fluids. Hence it is that protein +is required as a nutrient by the animal body, and it cannot be produced +from non-nitrogenous compounds. In vegetable bodies, the protein can be +produced synthetically from amids, which in turn are formed from +ammonium compounds. While protein is necessary in the ration, an +excessive amount should be avoided. When there is more than is needed +for functional purposes, it is used for heat and energy, and as foods +rich in protein are usually the most expensive, an excess adds +unnecessarily to the cost of the ration. Excess of protein in the ration +may also result in a diseased condition, due to imperfect elimination of +the protein residual products from the body.[10] + +22. Albuminoids differ from proteids in general composition and, to +some extent, in nutritive value. They are found in animal bodies mainly +in the connective tissue and in the skin, hair, and nails. Some of the +albuminoids, as nuclein, are equal in food value to protein, while +others have a lower food value. In general, albuminoids are capable of +conserving the protein of the body, and hence are called "protein +sparers," but they cannot in every way enter into the composition of the +body, as do the true proteins. + +23. Amids and Amines.--These are nitrogenous compounds of simpler +structure than the proteins and albuminoids. They are sometimes called +compound ammonia in that they are derived from ammonia by the +replacement of one of the hydrogen atoms with an organic radical. In +plants, amids are intermediate compounds in the production of the +proteids, and in some vegetables a large portion of the nitrogen is +amids. In animal bodies amids are formed during oxidation, digestion, +and disintegration of proteids. It is not definitely known whether or +not a protein in the animal body when broken down into amid form can +again be reconstructed into protein. The amids have a lower food value +than the proteids and albuminoids. It is generally held that, to a +certain extent, they are capable, when combined with proteids, of +preventing rapid conversion of the body proteid into soluble form. When +they are used in large amounts in a ration, they tend to hasten +oxidation rather than conservation of the proteids. + +24. Alkaloids.--In some plant bodies there are small amounts of +nitrogenous compounds called alkaloids. They are not found to any +appreciable extent in food plants. The alkaloids, like ammonia, are +basic in character and unite with acids to form salts. Many medicinal +plants owe their value to the alkaloids which they contain. In animal +bodies alkaloids are formed when the tissue undergoes fermentation +changes, and also during disease, the products being known as ptomaines. +Alkaloids have no food value, but act physiologically as irritants on +the nerve centers, making them useful from a medicinal rather than from +a nutritive point of view. To medical and pharmaceutical students the +alkaloids form a very important group of compounds. + +[Illustration: FIG. 5.--GRAPHIC COMPOSITION OF FLOUR. + +1, flour; 2, starch; 3, gluten; 4, water; 5, fat; 6, ash.] + +25. General Relationship of the Nitrogenous Compounds.--Among the +various subdivisions of the nitrogenous compounds there exists a +relationship similar to that among the non-nitrogenous compounds. From +proteids, amids and alkaloids may be formed, just as invert sugars and +their products are formed from sucrose. Although glucose products are +derived from sucrose, it is not possible to reverse the process and +obtain sucrose or cane sugar from starch. So it is with proteins, while +the amid may be obtained from the proteid in animal nutrition, as far +as known the process cannot be reversed and proteids be obtained from +amids. In the construction of the protein molecule of plants, nitrogen +is absorbed from the soil in soluble forms, as compounds of nitrates and +nitrites and ammonium salts. These are converted, first, into amids and +then into proteids. In the animal body just the reverse of this process +takes place,--the protein of the food undergoes a series of changes, and +is finally eliminated from the body as an amid, which in turn undergoes +oxidation and nitrification, and is converted into nitrites, nitrates, +and ammonium salts. These forms of nitrogen are then ready to begin +again in plant and animal bodies the same cycle of changes. Thus it is +that nitrogen may enter a number of times into the composition of plant +and animal tissues. Nature is very economical in her use of this +element.[5] + + + + +CHAPTER II + +CHANGES IN COMPOSITION OF FOODS DURING COOKING AND PREPARATION + + +26. Raw and Cooked Foods Compared.--Raw and cooked foods differ in +chemical composition mainly in the content of water. The amount of +nutrients on a dry matter basis is practically the same, but the +structural composition is affected by cooking, and hence it is that a +food prepared for the table often differs appreciably from the raw +material. Cooked meat, for example, has not the same percentage and +structural composition as raw meat, although the difference in nutritive +value between a given weight of each is not large. During cooking, foods +are acted upon chemically, physically, and bacteriologically, and it is +usually the joint action of these three agencies that brings about the +desirable changes incident to their preparation for the table. + +27. Chemical Changes during Cooking.--Each of the chemical compounds +of which foods are composed is influenced to a greater or less extent by +heat and modified in composition. The chemistry of cooking is mainly a +study of the chemical changes that take place when compounds, as +cellulose, starch, sugar, pectin, fat, and the various proteids, are +subjected to the joint action of heat, moisture, air, and ferments. The +changes which affect the cellulose are physical rather than chemical. A +slight hydration of the cellular tissue, however, does take place. In +human foods cellulose is not found to any appreciable extent. Many +vegetables, as potatoes, which are apparently composed of cellular +substances, contain but little true cellulose. Starch, as previously +stated, undergoes hydration in the presence of water, and, at a +temperature of 120 deg. C., is converted into dextrine. At a higher +temperature disintegration of the starch molecule takes place, with the +formation of carbon monoxid, carbon dioxid, and water, and the +production of a residue richer in carbon than is starch. On account of +the moisture, the temperature in many cooking operations is not +sufficiently high for changes other than hydration and preliminary +dextrinizing. In Chapter XI is given a more extended account of the +changes affecting starch which occur in bread making. + +During the cooking process sugars undergo inversion to a slight extent. +That is, sucrose is converted into levulose and dextrose sugars. At a +higher temperature, sugar is broken up into its constituents--water and +carbon dioxide. The organic acids which many fruits and vegetables +contain hasten the process of inversion. When sugar is subjected to dry +heat, it becomes a brown, caramel-like material sometimes called barley +sugar. During cooking, sugars are not altered in solubility or +digestibility; starches, however, are changed to a more soluble form, +and pectin--a jelly-like substance--is converted from a less to a more +soluble condition, as stated in Chapter I. Changes incident to the +cooking of fruits and vegetables rich in pectin, as in the making of +jellies, are similar to those which take place in the last stages of +ripening. + +The fats are acted upon to a considerable extent by heat. Some of the +vegetable oils undergo slight oxidation, resulting in decreased +solubility in ether, but since there is no volatilization of the fatty +matter, it is a change that does not materially affect the total fuel +value of the food.[11] + +There is a general tendency for the proteids to become less soluble by +the action of heat, particularly the albumins and globulins. The protein +molecule dissociates at a high temperature, with formation of volatile +products, and therefore foods rich in protein should not be subjected to +extreme heat, as losses of food value may result. During cooking, +proteids undergo hydration, which is necessary and preliminary to +digestion, and the heating need be carried only to this point, and not +to the splitting up of the molecule. Prolonged high temperature in the +cooking of proteids and starches is unnecessary in order to induce the +desired chemical changes. When these nutrients are hydrated, they are in +a condition to undergo digestion, without the body being compelled to +expend unnecessary energy in bringing about this preliminary change. +Hence it is that, while proper cooking does not materially affect the +total digestibility of proteids or starches, it influences ease of +digestion, as well as conserves available energy, thereby making more +economical use of these nutrients. + +[Illustration: FIG. 6.--CELLS OF A PARTIALLY COOKED +POTATO. (After KOeNIG.)] + +28. Physical Changes.--The mechanical structure of foods is influenced +by cooking to a greater extent than is the chemical composition. One of +the chief objects of cooking is to bring the food into better mechanical +condition for digestion.[12] Heat and water cause partial disintegration +of both animal and vegetable tissues. The cell-cementing materials are +weakened, and a softening of the tissues results. Often the action +extends still further in vegetable foods, resulting in disintegration of +the individual starch granules. When foods are subjected to dry heat, +the moisture they contain is converted into steam, which causes bursting +of the tissues. A good example of this is the popping of corn. Heat may +result, too, in mechanical removal of some of the nutrients, as the +fats, which are liquefied at temperatures ranging from 100 deg. to 200 deg. +F. Many foods which in the raw state contain quite large amounts of fat, +lose a portion mechanically during cooking, as is the case with bacon +when it is cut in thin slices and fried or baked until crisp. When foods +are boiled, the natural juices being of somewhat different density from +the water in which they are cooked, slight osmotic changes occur. There +is a tendency toward equalization of the composition of the juices of +the food and the water in which they are cooked. In order to achieve the +best mechanical effects in cooking, high temperatures are not necessary, +except at first for rupturing the tissues; softening of the tissues is +best effected by prolonged and slow heat. At a higher temperature many +of the volatile and essential oils are lost, while at lower temperatures +these are retained and in some instances slightly developed. The cooking +should be sufficiently prolonged and the temperature high enough to +effectually disintegrate and soften all of the tissues, but not to cause +extended chemical changes. + +[Illustration: FIG. 7.--CELLS OF RAW POTATO, SHOWING STARCH +GRAINS. (After KOeNIG.)] + +There is often an unnecessarily large amount of heat lost through faulty +construction of stoves and lack of judicious use of fuels, which greatly +enhances the cost of preparing foods. Ovens are frequently coated with +deposits of soot; this causes the heat to be thrown out into the room or +lost through the chimney, rather than utilized for heating the oven. In +an ordinary cook stove it is estimated that less than 7 per cent of the +heat and energy of the fuel is actually employed in bringing about +physical and chemical changes incident to cooking.[13] + +29. Bacteriological Changes.--The bacterial organisms of foods are +destroyed in the cooking, provided a temperature of 150 deg. F. is reached +and maintained for several minutes. The interior of foods rarely reaches +a temperature above 200 deg. F., because of the water they contain which is +not completely removed below 212 deg. One of the chief objects in cooking +food is to render it sterile. Not only do bacteria become innocuous +through cooking, but various parasites, as trichina and tapeworm, are +destroyed, although some organisms can live at a comparatively high +temperature. Cooked foods are easily re-inoculated, in some cases more +readily than fresh foods, because they are in a more disintegrated +condition. + +In many instances bacteria are of material assistance in the preparation +of foods, as in bread making, butter making, curing of cheese, and +ripening of meat. All the chemical compounds of which foods are +composed are subject to fermentation, each compound being acted upon by +its special ferment body. Those which convert the proteids into soluble +form, as the peptonizing ferments, have no action upon the +carbohydrates. A cycle of bacteriological changes often takes place in a +food material, one class of ferments working until their products +accumulate to such an extent as to prevent their further activity, and +then the process is taken up by others, as they find the conditions +favorable for development. This change of bacterial flora in food +materials is akin to the changes in the vegetation occupying soils. In +each case, there is a constant struggle for possession. Bacteria take a +much more important part in the preparation of foods than is generally +considered. As a result of their workings, various chemical products, as +organic acids and aromatic compounds, are produced. The organic acids +chemically unite with the nutrients of foods, changing their composition +and physical properties. Man is, to a great extent, dependent upon +bacterial action. Plant life also is dependent upon the bacterial +changes which take place in the soil and in the plant tissues. The +stirring of seeds into activity is apparently due to enzymes or soluble +ferments which are inherent in the seed. A study of the bacteriological +changes which foods undergo in their preparation and digestion more +properly belongs to the subject of bacteriology, and in this work only +brief mention is made of some of the more important parts which +microoerganisms take in the preparation of foods. + +30. Insoluble Ferments.--Insoluble ferments are minute, plant-like +bodies of definite form and structure, and can be studied only with the +microscope.[1] They are developed from spores or seeds, or from the +splitting or budding of the parent cells. Under suitable conditions they +multiply rapidly, deriving the energy for their life processes from the +chemical changes which they induce. For example, in the souring of milk +the milk sugar is changed by the lactic acid ferments into lactic acid. +In causing chemical changes, the ferment gives none of its own material +to the reacting substance. These ferment bodies undergo life processes +similar to plants of a higher order. + +[Illustration: FIG. 8.--LACTIC ACID BACTERIA, MUCH +ENLARGED. (After RUSSELL.)] + +All foods contain bacteria or ferments. In fact, it is impossible for a +food stored and prepared under ordinary conditions, unless it has been +specially treated, to be free from them. Some of them are useful, some +are injurious, while others are capable of producing disease. The +objectionable bacteria are usually destroyed by the joint action of +sunlight, pure air, and water. + +31. Soluble Ferments.--Many plant and animal cells have the power of +secreting substances soluble in water and capable of producing +fermentation changes; to these the term "soluble ferments," or +"enzymes," is applied. These ferments have not a cell structure like +the organized ferments. When germinated seed, as malted barley, is +extracted, a soluble and highly nitrogenous substance, called the +diastase ferment, is secured that changes starch into soluble forms. The +soluble ferments induce chemical change by causing molecular disturbance +or splitting up of the organic compounds, resulting in the production of +derivative products. They take an important part in animal and plant +nutrition, as by their action insoluble compounds are brought into a +soluble condition so they can be utilized for nutritive purposes. In +many instances ferment changes are due to the joint action of soluble +and insoluble ferments. The insoluble ferment secretes an enzyme which +induces a chemical change, modified by the further action of the soluble +ferment. Many of the enzymes carry on their work at a low temperature, +as in the curing of meat and cheese in cold storage.[14] + +32. General Relationship of Chemical, Physical, and Bacteriological +Changes.--It cannot be said that the beneficial results derived from +the cooking of foods are due to either chemical, physical, or +bacteriological change alone, but to the joint action of the three. In +order to secure a chemical change, a physical change must often precede, +and a bacteriological change cannot take place without causing a change +in chemical composition; the three are closely related and +interdependent. + +33. Esthetic Value of Foods.--Foods should be not only of good +physical texture and contain the requisite nutrients, but they should +also be pleasing to the eye and served in the most attractive manner. +Some foods owe a part of their commercial value to color, and when they +are lacking in natural color they are not consumed with a relish. There +is no objection to the addition of coloring matter to foods, provided it +is of a non-injurious character and does not affect the amount of +nutrients, and that its presence and the kind of coloring material are +made known. Some foods contain objectionable colors which are eliminated +during the process of manufacture, as in the case of sugar and flour. As +far as removal of coloring matter from foods during refining is +concerned, there can be no objection, so long as no injurious reagents +or chemicals are retained, as the removal of the color in no way affects +the nutritive value or permits fraud, but necessitates higher +purification and refining. The use of chemicals and reagents in the +preparation and refining of foods is considered permissible in all cases +where the reagents are removed by subsequent processes. In the food +decisions of the United States Department of Agriculture, it is stated: +"Not excluded under this provision are substances properly used in the +preparation of food products for clarification or refining and +eliminated in the further process of manufacture." [15] + + + + +CHAPTER III + +VEGETABLE FOODS + + +34. General Composition.--Vegetable foods, with the exception of +cereals, legumes, and nuts, contain a smaller percentage of protein than +animal food products. They vary widely in composition and nutritive +value; in some, starch predominates, while in others, sugar, cellulose, +and pectin bodies are most abundant. The general term "vegetable foods" +is used in this work to include roots, tubers, garden vegetables, +cereals, legumes, and all prepared foods of vegetable origin. + +35. Potatoes contain about 75 per cent of water and 25 per cent of dry +matter, the larger portion being starch. There is but little nitrogenous +material in the potato, only 2.25 per cent, of which about half is in +the form of proteids. There are ten parts of non-nitrogenous substance +to every one part of nitrogenous; or, in other words, the potato has a +wide nutritive ratio, and as an article of diet needs to be supplemented +with foods rich in protein. The mineral matter, cellular tissue, and +fat in potatoes are small in amount, as are also the organic acids. +Mechanically considered, the potato is composed of three parts,--outer +skin, inner skin, and flesh. The layer immediately beneath the outer +skin is slightly colored, and is designated the fibro-vascular layer. +The outer and inner skins combined make up about 10 per cent of the +weight of the potato. + +[Illustration: FIG. 9.--TRANSVERSE SECTION OF POTATO. +(After COWDEN and BUSSARD.) _a_, skin; _b_, cortical +layer; _c_, outer medullary layer; _d_, inner medullary layer.] + +A large portion of the protein of the potato is albumin, which is +soluble in water. When potatoes are peeled, cut in small pieces, and +soaked in water for several hours before boiling, 80 per cent of the +crude protein, or total nitrogenous material, is extracted, rendering +the product less valuable as food. When potatoes are placed directly in +boiling water, the losses of nitrogenous compounds are reduced to about +7 per cent, and, when the skins are not removed, to 1 per cent. +Digestion experiments show that 92 per cent of the starch and 72 per +cent of the protein are digested.[12] Compared with other foods, +potatoes are often a cheap source of non-nitrogenous nutrients. If used +in excessive amounts, however, they have a tendency to make the ration +unbalanced and too bulky. + + +MECHANICAL COMPOSITION OF THE POTATO + + ================================================ + |Per Cent + Unpeeled potatoes | 100.0 + Outer, or true skin | 2.5 + Inner skin, or fibro-vascular layer[A] | 8.5 + Flesh | 89.0 + ================================================ + + +CHEMICAL COMPOSITION OF THE POTATO + + ================================================================ + | | | | CARBOHYDRATES + |-----|-------|---|------------------------ + |Water| Crude |Fat|Nitrogen-free-| | + | |Protein| | extract |Fiber|Ash + | % | % | % | % | % |% + ---------------------|-----|-------|---|--------------|-----|--- + Outer, or true skin | 80.1| 2.7 |0.8| 14.|6 |1.8 + Inner skin, or | | | | | | + fibro-vascular | | | | | | + layer | 83.2| 2.3 |0.1| 12.6 | 0.7 |1.1 + Flesh | 81.1| 2.0 |0.1| 15.7 | 0.3 |0.8 + Average of 86 | | | | | | + American analyses[B]| 78.0| 2.2 |0.1| 18.|8 |0.9 + Average of 118 | | | | | | + European analyses[C]| 75.0| 2.1 |0.1| 21.0 | 0.7 |1.1 + ================================================================ + +[Footnote A: Including a small amount of flesh.] + +[Footnote B: From an unpublished compilation of analyses of American +food products.] + +[Footnote C: Koenig, "Chemie der Nahrungs-und Genussmittel," 3d ed., II, +p. 626.] + +36. Sweet Potatoes contain more dry matter than white potatoes, the +difference being due mainly to the presence of about 6 per cent of +sugar. There is approximately the same starch content, but more fat, +protein, and fiber. As a food, they supply a large amount of +non-nitrogenous nutrients. + +37. Carrots contain about half as much dry matter as potatoes, and +half of the dry matter is sugar, nearly equally divided between sucrose +and levulose, or fruit sugar. Like the potato, carrots have some organic +acids and a relatively small amount of proteids. In carrots and milk +there is practically the same per cent of water. The nutrients in each, +however, differ both as to kind and proportion. Experiments with the +cooking of carrots show that if a large amount of water is used, 30 per +cent or more of the nutrients, particularly of the more soluble sugar +and albumin, are extracted and lost in the drain waters.[12] The color +of the carrot is due to the non-nitrogenous compound carrotin, +C_{26}H_{38}. Carrots are valuable in a ration not because of the +nutrients they supply, but for the palatability and the mechanical +action which the vegetable fiber exerts upon the process of digestion. + +38. Parsnips contain more solid matter than beets or carrots, of which +3 to 4 per cent is starch. The starch grains are very small, being only +about one twentieth the size of the potato starch grains. There is 3 per +cent of sugar and an appreciable amount of fat, more than in any other +of the vegetables of this class, and seven times as much as in the +potato. The mineral matter is of somewhat different nature from that in +potatoes; in parsnips one half is potash and one quarter phosphoric +acid, while in potatoes three quarters are potash and one fifth +phosphoric acid. + +39. Cabbage contains very little dry matter, usually less than 10 per +cent. It is proportionally richer in nitrogenous compounds than many +vegetables, as about two of the ten parts of dry matter are crude +protein, which makes the nutritive ratio one to five. During cooking 30 +to 40 per cent of the nutrients are extracted. Cabbage imparts to the +ration bulk but comparatively little nutritive material. It is a +valuable food adjunct, particularly used raw, as in a salad, when it is +easily digested and retains all of the nutrients.[12] + +[Illustration: FIG. 10.--GRAPHIC COMPOSITION OF CABBAGE.] + +40. Cauliflower has much the same general composition as cabbage, from +which it differs mainly in mechanical structure. + +41. Beets.--The garden beet contains a little more protein than +carrots, but otherwise has about the same general composition, and the +statements made in regard to the losses of nutrients in the cooking of +carrots and to their use in the dietary apply also to beets. + +42. Cucumbers contain about 4 per cent of dry matter. The amount of +nutrients is so small as to scarcely allow them to be considered a food. +They are, however, a valuable food adjunct, as they impart palatability. + +43. Lettuce contains about 7 per cent of solids, of which 1.5 is +protein and 2.5 starch and sugar. While low in nutrients, it is high in +dietetic value, because of the chlorophyll which it contains. It has +been suggested that it is valuable, too, for supplying iron in an +organic form, as there is iron chemically combined with the chlorophyll. + +44. Onions are aromatic bulbs, valuable for condimental rather than +nutritive purposes. They contain essential and volatile oils, which +impart characteristic odor and flavor. In the onion there are about 1.5 +per cent of protein and 9.5 per cent of non-nitrogenous material. Onions +are often useful in stimulating the digestive tract to action. + +45. Spinach is a valuable food, not to be classed merely as a relish. +Its composition is interesting; for, although there is 90 per cent +water, and less than 10 per cent dry matter, it still possesses high +food value. Spinach contains 2.1 per cent crude protein, or about one +part to every four parts of carbohydrates. In potatoes, turnips, and +beets there are ten or more parts of carbohydrates to every one part of +protein. + +46. Asparagus is composed largely of water, about 93 per cent. The dry +matter, however, is richer in protein than that of many vegetables. +Asparagus contains, too, an amid compound, asparagin, which gives some +of the characteristics to the vegetable. + +47. Melons.--Melons contain from 8 to 10 per cent of dry matter, the +larger portion of which is sugar and allied carbohydrates. The flavor is +due to small amounts of essential oils and to organic acids associated +with the sugars. Melons possess condimental rather than nutritive value. + +[Illustration: FIG. 11.--GRAPHIC COMPOSITION OF TOMATO.] + +48. Tomatoes.--The tomato belongs to the night-shade family, and for +this reason was long looked upon with suspicion. It was first used for +ornamental purposes and was called "love-apple." Gradually, as the idea +of its poisonous nature became dispelled, it grew more and more popular +as a food, until now in the United States it is one of the most common +garden vegetables. It contains 7 per cent of dry matter, 4 per cent of +which is sucrose, dextrose, and levulose. It also contains some malic +acid, and a small amount of proteids, amids, cellulose, and coloring +material. In the canning of tomatoes, if too much of the juice is +excluded, a large part of the nutritive material is lost, as the sugars +and albumins are all soluble and readily removed.[16] If the seeds are +objectionable, they may be removed by straining and the juice added to +the fleshy portion. The product then has a higher nutritive value than +if the juice had been discarded with the seeds. + +49. Sweet Corn.--Fresh, soft, green, sweet corn contains about 75 per +cent of water. The dry matter is half starch and one quarter sugar. The +protein content makes up nearly 5 per cent, a larger proportional amount +than is found in the ripened corn, due to the fact that the proteids are +deposited in the early stages of growth and the carbohydrates mainly in +the last stages. Sweet corn is a vegetable of high nutritive value and +palatability. + +50. Eggplant contains a high per cent of water,--90 per cent. The +principal nutrients are starch and sugar, which make up about half the +weight of the dry matter. It does not itself supply a large amount of +nutrients, but the way in which it is prepared, by combination with +butter, bread crumbs, and eggs, makes it a nutritious and palatable +dish, the food value being derived mainly from the materials with which +it is combined, the eggplant giving the flavor and palatability. + +51. Squash and Pumpkin.--Squash has much the same general composition +and food value as beets and carrots, although it belongs to a different +family. Pumpkins contain less dry matter than squash. The dry matter of +both is composed largely of starch and sugar and, like many other of the +vegetables, they are often combined with food materials containing a +large amount of nutrients, as in pumpkin and squash pies, where the food +value is derived mainly from the milk, sugar, eggs, flour, and butter or +other shortening used. + +52. Celery.--The dry matter of celery is comparatively rich in +nitrogenous material, although the amount is small, and the larger +proportion is in non-proteid form. When grown on rich soil, celery may +contain an appreciable quantity of nitrates and nitrites, which have not +been converted into amids and proteids. The supposed medicinal value is +probably due to the nitrites which are generally present. Celery is +valuable from a dietetic rather than a nutritive point of view. + +53. Sanitary Condition of Vegetables.--The conditions under which +vegetables are grown have much to do with their value, particularly from +a sanitary point of view. Uncooked vegetables often cause the spread of +diseases, particularly those, as cholera and typhoid, affecting the +digestive tract. Particles of dirt containing the disease-producing +organisms adhere to the uncooked vegetable and find their way into the +digestive tract, where the bacteria undergo incubation. When sewage has +been used for fertilizing the land, as in sewage irrigation, the +vegetables are unsound from a sanitary point of view. Such vegetables +should be thoroughly cleaned and also well cooked, in order to render +them sterile. Vegetables to be eaten in the raw state should be dipped +momentarily into boiling water, to destroy the activity of the germs +present upon the surface. They may then be immediately immersed in +ice-cold water, to preserve the crispness. + +54. Miscellaneous Compounds in Vegetables.--In addition to the general +nutrients which have been discussed, many of the vegetables contain some +tannin, glucosides, and essential oils; and occasionally those grown +upon rich soils have appreciable amounts of nitrogen compounds, as +nitrates and nitrites, which have not been built up into proteids. +Vegetables have a unique value in the dietary, and while as a class they +contain small amounts of nutrients, they are indispensable for promoting +health and securing normal digestion of the food. + +55. Canned Vegetables.--When sound vegetables are thoroughly cooked to +destroy ferments, and then sealed in cans while hot, they can be kept +for a long time without any material impairment of nutritive value. +During the cooking process there is lost a part of the essential oils, +which gives a slightly different flavor to the canned or tinned +goods.[17] In some canned vegetables preservatives are used, but the +enactment and enforcement of national and state laws have greatly +reduced their use. When the cans are made of a poor quality of tin, or +the vegetables are of high acidity, some of the metal is dissolved in +sufficient quantity to be objectionable from a sanitary point of +view.[18] + +56. Edible Portion and Refuse of Vegetables.--Many vegetables have +appreciable amounts of refuse,[19] or non-edible parts, as skin, pods, +seeds, and pulp, and in determining the nutritive value, these must be +considered, as in some cases less than 50 per cent of the weight of the +material is edible portion, which proportionally increases the cost of +the nutrients. Ordinarily, the edible part is richer in protein than the +entire material as purchased. In some cases, however, the refuse is +richer in protein, but the protein is in a less available form. See +comparison of potatoes and potato skins. + + + + +CHAPTER IV + +FRUITS, FLAVORS, AND EXTRACTS + + +57. General Composition.--Fruits are characterized by containing a +large amount of water and only a small amount of dry matter, which is +composed mainly of sugar and non-nitrogenous compounds. Fruits contain +but little fatty material and protein. A large portion of the total +nitrogen is in the form of amid compounds. Organic acids, as citric, +tartaric, and malic, are found in all fruits, and the essential oils +form a characteristic feature. The taste of fruits is due mainly to the +blending of the various organic acids, essential oils, and sugars. +Although fruits contain a high per cent of water, they are nevertheless +valuable as food.[20] The constituents present to the greatest extent +are sugars and acids. The sugar is not all like the common granulated +sugar, but in ripe fruits a part is in the form known as levulose or +fruit sugar, which is two and a half times sweeter than granulated +sugar. Sugars are valuable for heat-and fat-producing purposes, but not +for muscle repairing. Proteids are the muscle-forming nutrients. The +organic acids, as malic acid in apples, citric acid in lemons and +oranges, and tartaric acid in grapes, have characteristic medicinal +properties. The sugar, proteid, and acid content of some of our more +common fruits is given in the following table:[21] + + +COMPOSITION OF FRUITS + + ============================================================== + | WATER |PROTEIDS| SUGAR |ACID IN |KIND OF + | | | | JUICE | ACID + ----------------|--------|--------|--------|--------|--------- + |Per Cent|Per Cent|Per Cent|Per Cent| + Apples (Baldwin)| 85.0 | 0.50 | 10.75 | 0.92 |Malic + Apples, sweet | 86.0 | 0.50 | 11.75 | 0.20 |Malic + Blackberries | 88.9 | 0.90 | 11.50 | 0.75 |Malic + Currants | 86.0 | -- | 1.96 | 5.80 |Tartaric + Grapes | 83.0 | 1.50 |10 to 16|1.2 to 5|Tartaric + Strawberries | 90.8 | 0.95 | 5.36 | 1.40 |Malic + Oranges | 85.0 | 1.10 | 10.00 | 1.30 |Citric + Lemons | 84.0 | 0.95 | 2.00 | 7.20 |Citric + ============================================================== + +In addition to sugars, acids, and proteids, there are a great many other +compounds in fruits. Those which give the characteristic taste are +called essential or volatile oils. + +58. Food Value.--When the nutrients alone are considered, fruits +appear to have a low food value, but they should not be judged entirely +on this basis, because they impart palatability and flavor to other +foods and exercise a favorable influence upon the digestive process. In +the human ration fruits are a necessary adjunct. + +59. Apples.--Apples vary in composition with the variety and physical +characteristics of the fruit. In general they contain from 10 to 16 per +cent of dry matter, of which 75 per cent, or more, is sugar or allied +carbohydrates. Among the organic acids malic predominates, and the +acidity ranges from 0.1 to 0.8 per cent. Apples contain but little +protein, less than 1 per cent. There is some pectin, or jelly-like +substance closely related to the carbohydrates. The flavor of the apple +varies with the content of sugar, organic acids, and essential oils. +During storage some apples appear to undergo further ripening, resulting +in partial inversion of the sucrose, and there is a slight loss of +weight, due to the formation of carbon dioxide. The apple is an +important and valuable adjunct to the dietary.[22] + +[Illustration: FIG. 12.--GRAPHIC COMPOSITION OF APPLE.] + +[Illustration: FIG. 13.--GRAPHIC COMPOSITION OF ORANGE.] + +60. Oranges contain nearly the same proportion of dry matter as +apples, the larger part of which is sugar. Citric acid predominates and +ranges in different varieties from 1 to 2.5 per cent. The amounts of +protein, fat, and cellulose are small. In some varieties of oranges +there is more iron and sulphur than is usually found in fruits. All +fruits, however, contain small amounts, but not as much as is found in +green vegetables. The average composition of oranges is as follows: + + =========================================================== + PHYSICAL COMPOSITION|CHEMICAL COMPOSITION OF EDIBLE PORTION + ----------------------------------------------------------- + Per Cent| Per Cent + Rind 20 to 30| Solids 10 to 16 + Pulp 25 to 35| Sugars 8 to 12 + Juice 35 to 50| Citric acid 1 to 2.5 + | Ash 0.5 + =========================================================== + +61. Lemons differ from oranges in containing more citric acid and less +sucrose, levulose, and dextrose. The ash of the lemon is somewhat +similar in general composition to the ash of the orange, but is larger +in amount. The average composition of the lemon is as follows: + + =========================================================== + PHYSICAL COMPOSITION|CHEMICAL COMPOSITION OF EDIBLE PORTION + ----------------------------------------------------------- + Per Cent| Per Cent + Rind 25 to 35| Solids 10 to 12 + Pulp 25 to 35| Sugar 2 to 4 + Juice 40 to 55| Citric acid 6 to 9 + =========================================================== + +62. Grape Fruit.--The rind and seed of this fruit make up about 25 per +cent, leaving 75 per cent as edible portion. The juice contains 14 per +cent solids, of which nearly 10 per cent is sugar and 2.5 per cent is +citric acid. There is more acid in grape fruit than in oranges and +appreciably less than in lemons. The characteristic flavor is due to a +glucoside-like material. Otherwise the composition and food value are +about the same as of oranges. + +[Illustration: FIG. 14.--GRAPHIC COMPOSITION OF STRAWBERRY.] + +63. Strawberries contain from 8 to 12 per cent of dry matter, mainly +sugar and malic acid. The protein, fat, and ash usually make up less +than 2 per cent. Essential oils and coloring substances are present in +small amounts. It has been estimated that it would require 75 pounds of +strawberries to supply the protein for a daily ration. Nevertheless they +are valuable in the dietary. It has been suggested that the malic and +other acids have antiseptic properties which, added to the appearance +and palatability, make them a desirable food adjunct. Strawberries have +high dietetic rather than high food value. + +64. Grapes contain more dry matter than apples or oranges. There is no +appreciable amount of protein or fat, and while they add some nutrients, +as sugar, to the ration, they do not contribute any quantity. Their +value, as in the case of other fruits, is due to palatability and +indirect effect upon the digestibility of other foods. In the juice of +grapes there is from 10 to 15 per cent or more of sugar, as sucrose, +levulose, and dextrose. Grapes contain also from 1 to 1.5 per cent of +tartaric acid, which, during the process of manufacture into wine, is +rendered insoluble by the alcohol formed, and the product, known as +argole, is used in the preparation of cream of tartar. Differences in +flavor and taste of grapes are due to variations in the sugar, acid, and +essential oil content. + +65. Peaches contain about 12 per cent of dry matter, of which over 10 +per cent is sugar and other carbohydrates. There is less than 1.5 per +cent of protein, fat, and mineral matter and about 0.5 per cent of acid. +The peach contains also a very small amount of hydrocyanic acid, which +is more liberally present in the kernel than in the fruit. Flavor is +imparted mainly by the sugar and essential oils. Peaches vary in +composition with variety and environment.[23] + +66. Plums contain the most dry matter of any of the fruits, about 22 +per cent, mainly sugar. About one per cent is acid and about 0.5 per +cent are protein and ash. There are a great many varieties of plums, +varying in composition. Dried plums (prunes) have mildly laxative +properties. + +67. Olives.--The ripe olive contains about 15 per cent of oil, +exclusive of the pit, which makes up 20 per cent of the weight. In +green, preserved olives there is considerably less oil. Because of the +oil the olive has food value. Olive oil is slightly laxative and assists +mechanically in the digestion of foods. + +68. Figs.--Dried figs contain about 50 per cent of sugar and 3.5 per +cent of protein. The fig has a mildly laxative action. + +69. Dried Fruits.--Many fruits are prepared for market by drying. The +dried fruit has a slightly different composition from the fresh fruit +because of loss of the volatile and essential oils, and minor chemical +changes which take place during the drying process. When free from +preservatives, dried fruits are valuable adjuncts to the dietary and can +be advantageously used when fresh fruits are not obtainable. + +70. Canning and Preservation of Fruits.--To obtain the best results in +canning, the fruit should not be overripe. After the ripened state has +been reached fermentation and bacterial changes occur, and it is more +difficult to preserve the fruit than when not so fully matured.[24] When +a fruit has begun to ferment, it is hard to destroy the ferment bodies +and their spores so as to prevent further ferment action. The chemical +changes that occur in the last stages of ripening are similar to those +which take place during the cooking process whereby the pectin or +jelly-like substances are rendered more soluble and digestible. + +71. Adulterated Canned Fruits.--Analyses of a number of canned fruits, +made by various Boards of Health, show the presence of small amounts of +arsenic, tin, lead, and other poisonous metals. The quantity dissolved +depends upon the kind, age, and condition of the canned goods and the +state of the fruit when canned. The longer a can of fruit or vegetable +has been kept in stock, the larger is the amount of tin or metal that +has been dissolved. When fresh canned, there is usually very little +dissolved tin, but in old goods the amount may be comparatively large. +The tin used for the can is occasionally of poor quality and may contain +some arsenic, which also is dissolved. The occasional use of canned +goods preserved in tin is not objectionable, but they should not be used +continually if it can be avoided. Preservatives, as borax, salicylic +acid, benzoic acid, and sodium sulphate, are sometimes added to prevent +fermentation and to preserve the natural appearance of the fruit or +vegetable.[18] + +72. Fruit Flavors and Extracts.--Formerly all fruit extracts and +flavors were obtained from vegetable sources; at present many are made +in the chemical laboratory by synthetic methods; that is, by combining +simpler organic compounds and radicals to produce the material having +the desired flavor and odor. The various fruit flavors are definite +chemical compounds, and can be produced in the laboratory as well as in +the cells of plants. When properly made, there is no difference in +chemical composition between the two. As prepared in the laboratory, +however, traces of acids, alkalies, and other compounds, used in +bringing about the necessary chemical combination, are often present, +not having been perfectly removed. Hence it is that natural and +artificial flavors differ mainly in the impurities which the artificial +flavors may contain. + +Some of the flavoring materials have characteristic medicinal +properties, as the flavor of bitter almond, which contains hydrocyanic +acid, a poisonous substance. Flavors and extracts should not be +indiscriminately used. In small amounts they often exert a favorable +influence upon the digestion of foods, and the value of some fruits is +in a large measure due to the special flavors they contain. A study of +the separate compounds which impart flavor to fruits, as the various +aldehydes, ethers, and organic salts, belongs to organic chemistry +rather than to foods. Some of the simpler compounds of which flavors are +composed may exist in entirely different form or combination in food +products; as for example, pineapple flavoring is ethyl butrate. This can +be prepared by combination of butyric acid from stale butter with +alcohol which supplies the ethyl radical. The chemical union of the two +produces the new compound, ethyl butrate, the distinctive flavoring +substance of the pineapple. Banana flavor can be made from stale +butter, caustic soda, and chloroform. None of these materials, as such, +go into the flavor, but an essential radical is taken from each. These +manufactured products, when properly made, are in every essential +similar to the flavor made by the plant and stored up in the fruit. The +plant combines the material in the laboratory of the plant cell, and the +manufacturer of essences puts together these same constituents in a +chemical laboratory. In the fruit, however, the essential oil is +associated with a number of other compounds. + + + + +CHAPTER V + +SUGARS, MOLASSES, SYRUP, HONEY, AND CONFECTIONS + + +73. Composition of Sugars.--The term "sugar" is applied to a large +class of compounds composed of the elements carbon, hydrogen, and +oxygen. Sugars used for household purposes are derived mainly from the +sugar cane and the sugar beet.[25] At the present time about two fifths +are obtained from the cane and about three fifths from the beet. When +subjected to the same degree of refining, there is no difference in the +chemical composition of the sugars from the two sources; they are alike +in every respect and the chemist is unable to determine their origin. +The production of sugar is an agricultural industry; the methods of +manufacture pertain more to industrial chemistry than to the chemistry +of foods, and therefore a discussion of them is omitted in this +work.[26] + +[Illustration: FIG. 15.--SUGAR CRYSTALS.] + +74. Commercial Grades of Sugar.--Sugars are graded according to the +size of the granule, the color and general appearance of the crystals, +and the per cent of sucrose or pure sugar. Common granulated sugar is +from 98.5 to 99.7 per cent pure sucrose. The impurities consist mainly +of moisture and mineral matter. In the process of refining, sulphur +fumes are frequently used for bleaching and clarifying the solution.[26] +The sulphurous acid formed is neutralized with lime, which is rendered +insoluble and practically all removed in subsequent filtrations. There +are, however, traces of sulphates and sulphites in ordinary sugar, but +these are in such small amounts as not to be injurious to health. When +sugar is burned, as in the bomb calorimeter, so as to permit collection +of all of the products of combustion, granulated sugar yields about 0.01 +of a per cent of sulphur dioxid.[13] Occasionally coloring substances, +as a small amount of indigo, are added to yellow tinged sugars to impart +a white color, much on the same principle as the bluing of clothes. The +amount used is usually extremely small, and the effect on health has +never been determined. Occasionally, however, bluing is used to such an +extent that a blue scum appears when the sugar is boiled with water. +Sugar has high value for the production of heat and energy. Digestion +experiments show that when it is used in the dietary in not excessive +amounts, it is directly absorbed by the body and practically all +available. It can advantageously be combined with other foods to form a +part of the ration.[27] When a ration contains the requisite amount of +protein, sugar is used to the best advantage. Alone it is incapable of +sustaining life, because it does not contain any nitrogen. When sugar +was substituted for an excess of protein in a ration, it was found to +produce heat and energy at much less expense. Many foods, as apples, +grapes, and small fruits, contain appreciable amounts of sugar and owe +their food value almost entirely to their sugar content. In the dietary, +sugar is too frequently regarded as a condiment instead of a nutrient, +to be used for imparting palatability rather than for purposes of +nutrition. While valuable for improving the taste of foods, the main +worth of sugar is as a nutritive substance; used in the preparation of +foods it adds to the total heat and energy of the ration. Sugar is +sometimes used in excessive amounts and, as is the case with any food or +nutrient, when that occurs, nutrition disturbances result, due to misuse +of the food. Statistics show that the average consumption of sugar in +the United States is nearly 70 pounds a year per capita. In the dietary +of the adult, sugar to the extent of four ounces per day can be consumed +advantageously. The exclusion of sugar from the diet of children is a +great mistake, as they need it for heat and energy and to conserve the +protein for growth. + + "Sugar is one of the most important forms in which carbohydrates + can be added to the diet of children. The great reduction in the + price of sugar which has taken place in recent years is probably + one of the causes of the improved physique of the rising + generation. The fear that sugar may injure children's teeth is, + largely illusory. The negroes who live largely on sugar cane have + the finest teeth the world can show. If injudiciously taken, sugar + may, however, injure the child's appetite and digestion. The + craving for sweets which children show is no doubt the natural + expression of a physiological need, but they should be taken with, + and not between, meals."[28] + +[Illustration: FIG. 16.--NUTRIENTS OF A RATION WITH SUGAR. + +The hacket parts represent the proportion of nutrients not digested.] + +75. Sugar in the Dietary.--Sugar has an important place in the +dietary. It not only serves for the production of heat and energy in the +body, but is also valuable in enabling the proteids to be used more +economically. In reasonable amounts, it is particularly valuable in the +dietary of growing children, as the proteids of the food are then +utilized to better advantage for growth. The unique value of sugar +depends upon its intelligent use and its proper combination with other +foods, particularly with those rich in the nitrogenous compounds or +proteids. Sugar alone is incapable of sustaining life, but combined with +other foods is a valuable nutrient. The amount which can be +advantageously used depends largely upon the individual. Ordinarily +three to five ounces per day is sufficient, although some persons cannot +safely consume as much as this. In the case of diabetes mellitus, the +amount of sugar in the ration must be materially reduced. Persons in +normal health and engaged in outdoor work can use sugar to +advantage.[29] Many of the "harvest drinks," made largely from molasses +with a little ginger, and used extensively in some localities, are not +without merit, as they contain an appreciable amount of nutrients. Milk +contains more sugar as lactose or milk sugar than any other nutrient. + +[Illustration: FIG. 17.--NUTRIENTS OF A RATION WITHOUT SUGAR. + +The hacket parts represent the proportion of nutrients not digested.] + +The craving for sugar by growing children and athletes is natural. +Sugar, however, is often injudiciously used, and a perverted taste may +be established which can be satisfied only by excessive amounts. This +results in impaired digestion and malnutrition. + +76. Maple Sugar.--Sugar obtained by evaporation from the sap of the +maple tree (_Acer saccharinum_) is identical, except for the foreign +substances which it contains, with that from the beet and sugar cane. +The mottled appearance and characteristic color and taste of maple sugar +are due to the various organic acids and other compounds present in the +maple sap and recovered in the sugar. Maple sugar, as ordinarily +prepared, has 0.4 of a per cent or more of ash or mineral matter, while +refined cane sugar contains less than one tenth as much.[30] Hence, when +maple sugar is adulterated with cane and beet sugars, the ash content is +noticeably lowered, as is also the content of organic acids. It is +difficult, however, to determine with absolute certainty pure high grade +maple sugar from the impure low grade to which a small amount of +granulated sugar has been added. + +77. Adulteration of Sugar.--Sugar at the present time is not +materially adulterated. Other than the substances mentioned which are +used for clarification and color, none are added during refining which +remain in the sugar in appreciable amounts. Sugar does not readily lend +itself to adulteration, as it has a definite crystalline structure, and +materials that would be suitable for its adulteration are of entirely +different physical character.[31] Cane sugar is not easily blended with +glucose, or starch sugar, because of the physical differences between +the two. The question of the kind of sugar to use in the household, as +granulated, loaf, or pulverized, is largely one of personal choice, as +there is no appreciable difference in the nutritive value or purity of +the different kinds. + +78. Dextrose Sugars.--Products known as glucose and dextrose sugars +are made from corn and other starches; they can also be prepared from +cane sugar by the use of heat, chemicals, or ferments for carrying on +the process known as inversion. The dextrose sugars differ from cane +sugar in containing a dissimilar number of carbon, hydrogen, and oxygen +atoms in the molecule. The formula of the dextrose sugars is +C_{6}H_{12}_O{6}, while that of cane sugar is C_{12}H_{22}O_{11}. By the +addition of one molecule of water, H_{2}O, to a molecule of sucrose, two +molecules of invert sugar (dextrose and glucose) are produced:[1] +C_{12}H_{22}O_{11} + H_{2} = C_{6}H_{12}O_{6} + C_{6}H_{12}O_{6}. In +bringing about this change, acids are employed, but the acid in no way +enters into the chemical composition of the final product; it is removed +as described during the process of sugar manufacture. The action of the +acid brings about a catalytic change, the acid being necessary only as a +presence reagent to start the chemical reaction. When properly prepared +and the acid product thoroughly removed, dextrose and glucose have +practically the same food value as sugar. When they are digested, heat +and energy are produced, and a given weight has about the same fuel +value as an equal weight of sugar. Some of the glucose-yielding products +can be made at less expense than sugar, and when they are sold under +their right names there is no reason why they should not be used in the +dietary, as they serve the same nutritive purpose. + +79. Molasses is a by-product obtained in the refining of sugar. It is +a mixture of cane sugar and invert sugars, as levulose and dextrose. +When in sugar making the sucrose is removed by crystallization, a point +is finally reached where the solution, or mother liquid, as it is +called, refuses to give up any further crystals;[31] then this product, +consisting of various sugars and small amounts of organic acids and ash, +is partially refined and clarified to form molasses. The term "New +Orleans" molasses was formerly applied to the product obtained by the +use of open kettles for the manufacture of sugar, but during recent +years the vacuum pan process has been introduced, and "New Orleans" +molasses is now an entirely different article. The terms first, second, +and third molasses are applied to the liquids obtained after the removal +of the first, second, and third crops of sugar crystals; first molasses +being richer in sucrose, while third molasses is richer in dextrose and +invert sugars. The ash in molasses ranges from 4 to 6.5 per cent. Some +of the low grades of molasses are used in the preparation of animal +foods. + +The taste and physical characteristics of molasses are due largely to +the organic acids and impurities that are present, as well as to the +proportion in which the various sugars occur. When used with soda in +cooking and baking operations, the organic acid of the molasses +liberates carbon dioxide gas, which acts as a leavening agent. Because +of the organic acids, molasses should not be stored in tin or metalware +dishes, as the solvent action results in producing poisonous tin and +other metallic salts. + +The food value of molasses is dependent entirely upon the amount of dry +matter and the per cent of sugar. A large amount of water is considered +an adulterant; ordinarily molasses contains from 20 to 33 per cent. If a +sample of molasses contains 75 per cent of dry matter, it has slightly +less than three fourths of the nutritive value of the same weight of +sugar. + +80. Syrups.--The term "syrup" is applied to natural products obtained +by evaporation and purification of the saccharine juices of plants. +Sorghum syrup is from the sorghum plant, which is pressed by machinery +and the juice clarified and evaporated so as to contain about 25 per +cent of water. In sorghum syrups there are from 30 to 45 per cent of +cane sugar, and from 12 to 20 per cent of glucose and invert sugars. +Cane syrup is made from the clarified juice of the sugar cane, and has +about the same general composition as sorghum syrup. Maple syrup, +prepared from the juice of the sugar maple, is characteristically rich +in sucrose and contains but little glucose or reducing sugars. The +flavor of all the syrups is due mainly to organic acids, ethereal +products, and impurities. In some instances the essential flavor can be +produced synthetically, or derived from other and cheaper materials; +and by the use of these flavors, mixed syrups can be prepared closely +resembling many of the natural products. When properly made, they are +equal in nutritive value to natural syrups. When sold under assumed +names, they are to be considered and classified as adulterated, and not +as syrups from definite and specific products. Low-grade syrups and +molasses are often used for making fuel alcohol. They readily undergo +alcoholic fermentation and are valuable for this purpose, rendering it +possible for a good grade of fuel alcohol to be produced at low cost. +The manufacture of sugar, syrups, and molasses has been brought to a +high degree of perfection through the assistance rendered by industrial +chemistry. Losses in the process are reduced to a minimum, and the +various steps are all controlled by chemical analysis. Sugar has the +physical property of deflecting a ray of polarized light, the amount of +deflection depending upon the quantity of sugar in solution. This is +measured by the polariscope, an instrument by means of which the sugar +content of sugar plants is rapidly determined. + +[Illustration: FIG. 18.--GRAPHIC COMPOSITION OF +SYRUP.] + +81. Honey is composed largely of invert sugars gathered by the +honeybee from the nectar of flowers. It varies in composition and flavor +according to its source. The color depends upon the flower from which it +came, white clover giving a light-colored, pleasant-flavored honey, +while that from buckwheat and goldenrod is dark and has a slightly rank +taste. The comb is composed largely of wax, which has somewhat the same +general composition as fat, but contains ethereal instead of glycerol +bodies. On account of the predominance of invert sugars, pure honey has +a levulo or left-handed rotation when examined by the polariscope. Honey +contains from 60 to 75 per cent of invert sugars, and from 12 to 20 per +cent of water, while the ash content is small, less than one tenth of +one per cent. Strained honey is easily adulterated with glucose +products. Adulteration with cane sugar is readily detected, as pure +honey contains only a very small amount of sucrose. Honey can be made by +feeding bees on sugar; the sugar undergoes inversion, with the +production of dextrose. Such honey, although not adulterated, is +inferior in quality and lacking in natural flavor.[18] + +82. Confections.--By blending various saccharine products, confections +are made. Usually sucrose (cane and beet sugar) is used as the basis for +their preparation. Sucrose has definite physical properties, as +crystalline structure, and forms chemical and mechanical combinations +with acid, alkaline, and other substances; it also unites with water, +and when heated undergoes changes in structural composition. The +presence of small amounts of acid substances, or variations in the +concentration of the sugar solution, materially affect the mechanical +relation of the sugar particles to each other, and their +crystallization. Usually crystallization takes place when there is less +than 25 per cent of water present. The form, size, and arrangement of +the crystals are influenced by agitation during cooling. To secure +desired results, often small quantities of various other substances are +employed for their mechanical action. Glucose is frequently used, and is +said to be necessary for the production of some kinds of candy. + +Candies are colored with various dyes and pigments, many of which are +harmless, although some are injurious. Coal tar dyes are frequently +employed for this purpose. Objection has generally been urged against +their use, as it is believed many of them are injurious to health. It +cannot be said, however, that all are poisonous, as some are known to be +harmless. The use of a few coal tar dyes is allowed by the United States +government. Mineral colors are now rarely, if ever, used. + +Impure candies result from objectionable ingredients, as starch, +paraffin, and large amounts of injurious coloring substances. Coal tar +coloring materials are identified in the way described in Experiment No. +13. Confectionery, when properly prepared and unadulterated, has the +same nutritive value as sugar and the other ingredients, and is entitled +to a place in the dietary for the production of heat and energy. Much +larger amounts of candies are sold and consumed during the winter than +the summer months, suggesting that in cold weather candy is most needed +in the dietary. + +83. Saccharine is an artificial sweetening, five hundred times sweeter +than cane sugar. It contains in its molecule, chemically united, +benzine, sulphuric acid, and ammonia radicals. It is employed for +sweetening purposes in cases of diabetes mellitus, where physicians +advise against the use of sugar. It has no food value. A small amount is +sometimes added to canned corn and tomatoes to impart a sweet taste. The +physiological properties of saccharine have not been extensively +investigated. + + + + +CHAPTER VI + +LEGUMES AND NUTS + + +84. General Composition of Legumes.--Peas, beans, lentils, and peanuts +are the legumes most generally used for human food. As a class, they are +characterized by high protein content and a comparatively low per cent +of starch and carbohydrates. They contain the largest amount of +nitrogenous compounds of any of the vegetable foods, and hence are +particularly valuable in the human ration as a substitute for meats.[32] +For feeding animals the legumes are highly prized, particularly the +forage crops, clover and alfalfa. These secure their nitrogen, which is +the characteristic element of protein, from the free nitrogen of the +air, through the workings of bacterial organisms found in the nodules on +the roots of the plants. The legumes appear to be the only plants +capable of making use of the nitrogen of the air for food purposes. + +85. Beans contain about 24 per cent of protein and but little fat, +less than is found in any of the grain or cereal products. The protein +of the bean differs from that of cereals in its general and structural +composition. It is a globulin known as legumin, and is acted upon +mainly by ferments working in alkaline solutions, as in the lower part +of the digestive tract. Beans have about the same amount of ash as the +cereals, but the ash is richer in potash and lime. + +[Illustration: FIG. 19.--GRAPHIC COMPOSITION OF BEANS. +HACKED PART INDIGESTIBLE.] + +86. Digestibility of Beans.--Beans are usually considered +indigestible, but experiments show they are quite completely digested, +although they require more work on the part of the digestive tract than +many other foods. The digestibility was found to vary with individuals, +86 per cent of the protein being digested in one case, and only 72 per +cent in another. The protein of beans is not as completely digested as +that of meats. When beans were combined with other foods, forming a part +of a ration, they were more completely digested than when used in large +amounts and with only a few other foods. The presence of the skin is in +part responsible for low digestibility. When in the preparation of beans +the skins, which contain a large amount of cellulose, are removed, the +beans are more completely digested. By cooking from twenty minutes to +half an hour in rapidly boiling water containing a small amount of soda, +the skins are softened and loosened and are then easily removed by +rubbing in cold water. Some of the soda enters into combination with the +legumin. Along with the skins a portion of the germ is lost. The germ +readily ferments, which is probably the cause of beans producing +flatulence with some individuals during digestion. After the skins are +removed the nutrients are more susceptible to the action of the +digestive fluids. Experiments show that 42 per cent of the protein of +baked skinned beans is soluble in pepsin and pancreatin solutions, while +under similar conditions there is only 3.85 per cent of the protein +soluble from beans baked without removal of the skins. + +[Illustration: FIG. 20.--BEANS, RAW AND COOKED. SKINS, WET +AND DRY.] + +87. Use of Beans in the Dietary.--There is no vegetable food capable +of furnishing so much protein at such low cost as beans; from a pound +costing five cents about one fifth of a pound of protein and three +fifths of a pound of carbohydrates are obtained. Beans can, to a great +extent, take the place of meats in the dietary. There is more protein in +beans than in beef. Four ounces of uncooked beans or six ounces of baked +beans are as much as can conveniently be combined in the dietary, and +these will furnish a quarter of the protein of the ration. In the case +of active out-of-door laborers over a pound of baked beans per day is +often consumed with impunity. + +88. String Beans.--String beans--green beans with pod--contain a large +amount of water, 85 to 88 per cent. The dry matter is rich in protein, +nearly 20 per cent, although in the green beans as eaten, containing 85 +per cent water, there is less than 2-1/2 per cent. Lima beans are richer +in protein than string beans, as the green pod is not included. String +beans are valuable both for the nutrients they contain and for the +favorable influence they exert upon the digestibility of other foods. + +89. Peas.--In general composition and digestibility, peas are quite +similar to beans. They belong to the same family, Leguminosae, and the +protein of each is similar in quantity and general properties. The +statements made in regard to the composition, digestibility, and use of +beans in the dietary apply with minor modifications to peas. When used +in the preparation of soups, they add appreciable amounts of nutrients. + +[Illustration: FIG. 21.--PEA STARCH GRANULES.] + +90. Canned Peas.--In order to impart a rich green color, copper +sulphate has been used in the canning of peas. Physiologists differ as +to its effect upon health. While a little may not be particularly +injurious, much interferes with normal digestion of the food and forms +insoluble copper proteids. In some countries a small amount of copper +sulphate is tolerated, while in others it is prohibited. + +91. Peanuts.--Peanuts differ from peas and beans in containing more +fat. They should be considered a food, for at ordinary prices they +furnish a large amount of protein and fat. Like the other members of the +legume family, the peanut is rather slow of digestion and requires +considerable intestinal work for completion of the process. + + +NUTS + +92. General Composition.--Nuts should be regarded as food, for they +contribute to a ration appreciable amounts of nutrients. The edible +portion of nearly all is rich in fat; pecans, for example, contain as +high as 70 per cent. In protein content nuts range from 3 per cent in +cocoanuts to 30 per cent in peanuts. The carbohydrate content is usually +comparatively low, less than 5 per cent in hickory nuts, although there +is nearly 40 per cent in chestnuts. On account of high fat content, nuts +supply a large amount of heat and energy.[33] + +93. Chestnuts are characterized by containing less fat and protein and +much more carbohydrate material, especially starch, than is found in +other nuts. In southern Europe chestnuts are widely used as food; the +skins are removed, and the nuts are steamed, boiled, or roasted, and +sometimes they are dried and ground into flour. Chestnuts are less +concentrated in protein and fat, and form a better balanced food used +alone than do other nuts. + +94. The Hickory Nut, which is a characteristically American nut, +contains in the edible portion about 15 per cent protein, 65 per cent +fat, and 12 per cent carbohydrates. + +95. The Almonds used in the United States come chiefly from southern +Europe, although they are successfully raised in California. They +contain about 55 per cent fat and 22 per cent protein. The flavor of +almonds is due to a small amount of hydrocyanic acid. + +96. Pistachio.--Some nuts are used for imparting color and flavor to +food products, as the pistachio nut, the kernel of which is greenish in +color and imparts a flavor suggestive of almonds. The pistachio has high +food value, as it is rich in both fat and protein. It is employed in the +manufacture of confectionery and in ice cream for imparting flavor and +color. + +97. Cocoanuts grow luxuriantly in many tropical countries, and have a +high food value. They are characteristically rich in fat, one half of +the edible portion being composed of this nutrient. For tropical +countries they supply the fat of a ration at less expense than any other +food. When used in large amounts they should be supplemented with foods +rich in carbohydrates, as rice, and in proteids, as beans. Cocoanut milk +is proportionally richer in carbohydrates and poorer in fat and protein +than the meat of the cocoanut. In discussing the cocoanut, Woods +states:[34] + + "The small, green, and immature nuts are grated fine for medicinal + use, and when mixed with the oil of the ripe nut it becomes a + healing ointment. The jelly which lines the shell of the more + mature nut furnishes a delicate and nutritious food. The milk in + its center, when iced, is a most delicious luxury. Grated cocoanut + forms a part of the world-renowned East India condiment, curry. + Dried, shredded (desiccated) cocoanut is an important article of + commerce. From the oil a butter is made, of a clear, whitish color, + so rich in fat, that of water and foreign substances combined there + are but O.0068. It is better adapted for cooking than for table + use. At present it is chiefly used in hospitals, but it is rapidly + finding its way to the tables of the poor, particularly as a + substitute for oleomargarine." + +98. Use of Nuts in the Dietary.--When nuts can be secured at a low +price per pound, ten cents or less, they compare favorably in nutritive +value with other staple foods. Digestion experiments with rations +composed largely of nuts show that they are quite thoroughly digested. +Professor Jaffa of the California Experiment Station, in discussing the +nutritive value of nuts and fruits, says:[35] + + "It is certainly an error to consider nuts merely as an accessory + to an already heavy meal, and to regard fruit merely as something + of value for its pleasant flavor, or for its hygienic or medicinal + virtues. The agreement of one food or another with any person is + more or less a personal idiosyncrasy, but it seems fair to say that + those with whom nuts and fruits agree, can, if they desire, readily + secure a considerable part of their nutritive material from such + sources." + + +AVERAGE COMPOSITION OF NUTS + +(From Fifteenth Annual Report, Maine Agricultural Experiment Station.) + + =========================================================================== + |REFUSE|EDIBLE | EDIBLE PORTION |VALUE[A] + | | |------------------------------| + | |PORTION|Water|Prot.| Fat |Carb.| Ash | PER LB. + --------------------------------------------------------------------------- + | % | % | % | % | % | % | % |Calories + Almonds | 64.8 | 35.2 | 1.7 | 7.3 |19.3 | 6.2 | 0.7 | 1065 + Almonds, kernels | -- | 100.0 | 4.8 |21.0 |54.9 |17.3 | 2.0 | 3030 + Brazil nuts | 49.6 | 50.4 | 2.7 | 8.6 |33.6 | 3.5 | 2.0 | 1545 + Filberts | 52.1 | 47.9 | 1.8 | 7.5 |31.3 | 6.2 | 1.1 | 1575 + Filberts, kernels | -- | 100.0 | 3.7 |15.6 |65.3 |13.0 | 2.4 | 3290 + Hickory nuts | 62.2 | 37.8 | 1.4 | 5.8 |25.5 | 4.3 | 0.8 | 1265 + Pecans | 49.7 | 50.3 | 1.4 | 5.2 |35.6 | 7.2 | 0.8 | 1733 + Pecans, kernels | -- | 100.0 | 2.9 |10.3 |70.8 |14.3 | 1.7 | 3445 + Walnuts | 58.0 | 42.0 | 1.2 | 7.0 |27.0 | 6.1 | 0.7 | 1385 + Walnuts, kernels | -- | 100.0 | 2.8 |16.7 |64.4 |14.8 | 1.3 | 3305 + Chestnuts | 16.1 | 83.9 |31.0 | 5.7 | 6.7 |39.0 | 1.5 | 1115 + Acorns | 35.6 | 64.4 | 2.6 | 5.2 |24.1 |30.9 | 1.6 | 1690 + Beechnuts | 40.8 | 59.2 | 2.3 |13.0 |34.0 | 7.8 | 2.1 | 1820 + Butternuts | 86.4 | 13.6 | 0.6 | 3.8 | 8.3 | 0.5 | 0.4 | 430 + Litchi nuts | 41.6 | 58.4 |10.5 | 1.7 | 0.1 |45.2 | 0.9 | 875 + Pinon, P. edulis | 40.6 | 59.4 | 2.0 | 8.7 |36.8 |10.2 | 1.7 | 1905 + Pinon, P. monophylla| 41.7 | 58.3 | 2.2 | 3.8 |35.4 |15.3 | 1.6 | 1850 + Pinon, P. sabiniana | 77.0 | 23.0 | 1.2 | 6.5 |12.3 | 1.9 | 1.1 | 675 + Pistachio, kernels | -- | 100.0 | 4.2 |22.6 |54.5 |15.6 | 3.1 | 3010 + Peanuts, raw | 26.4 | 73.6 | 6.9 |20.6 |30.7 |13.8 | 1.6 | 1935 + Peanuts, kernels | -- | 100.0 | 9.3 |27.9 |42.0 |18.7 | 2.1 | 2640 + Roasted peanuts | 32.6 | 67.4 | 1.1 |20.6 |33.1 |10.9 | 1.7 | 1985 + Shelled peanuts | -- | 100.0 | 1.6 |30.5 |49.2 |16.2 | 2.5 | 2955 + Peanut butter | -- | -- | 2.0 |29.3 |46.6 |17.1 |[B]5.0| 2830 + Cocoanuts | 48.8 | 51.2 | 7.2 | 2.9 |25.9 |14.3 | 0.9 | 1415 + Cocoanuts, shredded | -- | -- | 3.5 | 6.3 |57.3 |31.6 | 1.3 | 3125 + Cocoanut milk | -- | -- |92.7 | 0.4 | 1.5 | 4.6 | 0.8 | 97 + ========================================================================= + +[Footnote A: Calculated from analyses.] + +[Footnote B: Including salt, 4.1.] + + + + +CHAPTER VII + +MILK AND DAIRY PRODUCTS + + +99. Importance in the Dietary.--There is no article of food which +enters so extensively into the dietary as milk, and it is one of the few +foods which supply all the nutrients,--fats, carbohydrates, and +proteids.[36] Milk alone is capable of sustaining life for comparatively +long periods, and it is the chief article of food during many diseases. +An exclusive milk diet for a healthy adult, however, would be +unsatisfactory; in the case of young children, milk is essential, +because the digestive tract has not become functionally developed for +the digestion of other foods. + +It is necessary to consider not only the composition and nutritive value +of milk, but also its purity or sanitary condition. + +100. General Composition.--Average milk contains about 87 per cent +water and 13 per cent dry matter. The dry matter is composed +approximately of: + + ======================= + | Per Cent + Fat | 3.5 + Casein | 3.25 + Albumin | 0.50 + Milk sugar | 5.00 + Ash | 0.75 + ======================= + +[Illustration: FIG. 22.--MILK FAT GLOBULES.] + +Fat is the most variable constituent of milk. Occasionally it is found +as low as 2 per cent and as high as 6 per cent or more. The poorest and +richest milks differ mainly in fat content, as the sugar, ash, casein, +and albumin, or "solids of the milk serum," are fairly constant in +amount and composition. Variations in the content of fat are due to +differences in feed and in the breed and individuality of the animal. + +101. Digestibility.--Milk is one of the most completely digested of +foods, about 95 per cent of the protein and fat and 97 per cent of the +carbohydrates being absorbed and utilized by the body. + +In a mixed ration, the nutrients of milk are practically all absorbed. +Milk also exerts a favorable influence upon the digestibility of other +foods with which it is combined. This is doubtless due to the digestive +action of the special ferments or enzymes which milk contains. In milk +there is a soluble ferment material or enzyme which has the power of +peptonizing proteids. It is this ferment which carries on the ripening +process when cheese is cured in cold storage, and it is believed to be +this body which promotes digestion of other foods with which milk is +combined.[27] + +Milk is not easily digested by some persons. The tendency to costiveness +caused by a milk diet can be largely overcome by the use of salt with +the milk, or of some solid food, as toast or crackers, to prevent +coagulation and the formation of masses resistant to the digestive +fluids. Barley water and lime water in small amounts are also useful for +assisting mechanically in the digestion of milk. Milk at ordinary prices +is one of the cheapest foods that can be used. + +[Illustration: FIG. 23.--DIRT IN A SAMPLE OF UNSANITARY MILK.] + +102. Sanitary Condition of Milk.--Equally as important as composition +is the sanitary condition or wholesomeness of milk. Milk is a food +material which readily undergoes fermentation and is a medium for the +distribution of germ diseases. The conditions under which it is produced +and the way in which it is handled determine largely its sanitary +value, and are of so much importance in relation to public health that +during recent years city and state boards of health have introduced +sanitary inspection and examination of milk along with the chemical +tests for detecting its adulteration. Some of the more frequent causes +of contaminated and unsound milk are: unhealthy animals, poor food and +water, unsanitary surroundings of the animals, and lack of cleanliness +and care in the handling and transporting of the milk. Outbreaks of +typhoid and scarlet fevers and other germ diseases have frequently been +traced to a contaminated milk supply.[37] + +103. Certified Milk.--When milk is produced under the most sanitary +conditions, the number of bacterial bodies per cubic centimeter is +materially reduced. In order to supply high grade milk containing but +few bacteria, special precautions are taken in the care of the animals, +and in the feeding and milking, and all sources of contamination of the +milk are eliminated as far as possible. Such milk, when sold in +sterilized bottles, is commonly called "certified milk," indicating that +its purity is guaranteed by the producer and that the number of bacteria +per unit does not exceed a certain standard, as 8000 per cubic +centimeter. Ordinary market milk contains upwards of 50,000. + +104. Pasteurized Milk.--In order to destroy the activity of the +bacterial organisms, milk is subjected to a temperature of 157 deg. F. for +ten minutes or longer, which process is known as pasteurization. When +milk is heated to a temperature above 180 deg., it is sterilized. Below +157 deg., the albumin is not coagulated. By pasteurizing, milk is much +improved from a sanitary point of view, and whenever the milk supply is +of unknown purity, it should be pasteurized.[38] After the milk has been +thus treated, the same care should be exercised in keeping it protected +to prevent fresh inoculation or contamination, as though it were +unpasteurized milk. For family use milk can be pasteurized in small +amounts in the following way: Before receiving the milk, the receptacle +should be thoroughly cleaned and sterilized with boiling water or dry +heat, as in an oven. The milk is loosely covered and placed in a pan of +water, a false bottom being in the pan so as to prevent unequal heating. +The water surrounding the milk is gradually heated until a temperature +of 159 deg. F. is registered, and the milk is kept at this temperature for +about ten minutes. It is then cooled and placed in the refrigerator. + +[Illustration: FIG. 24.--PASTEURIZING MILK.] + +105. Tyrotoxicon.--Tyrotoxicon is a chemical compound produced by a +ferment body which finds its way into milk when kept in unsanitary +surroundings. It induces digestion disorders similar to cholera, and +when present in large amounts, may prove fatal. It sometimes develops in +cream, ice cream, or cheese, but only when they have been kept in +unclean places or produced from infected milk. + +601. Color of Milk is often taken as a guide to its purity and +richness in fat. While a yellow tinge is usually characteristic of +milks rich in fat, it is not a hard and fast rule, for frequently +light-colored milks are richer in fat than yellow-tinged ones. The +coloring material is independent of the percentage of fat, and it is not +always safe to judge the richness of milk on the basis of color. + +107. Souring of Milk.--Souring of milk is due to the action of the +lactic acid organism, which finds its way into the milk through +particles of dust carried in the air or from unclean receptacles which +contain the spores of the organism.[39] When milk sours, a small amount +of sugar is changed to lactic acid which reacts upon the casein, +converting it from a soluble to an insoluble condition. When milk is +exposed to the air at a temperature of from 70 deg. to 90 deg. F., lactic +acid fermentation readily takes place. At a low temperature the process +is checked, and at a high temperature the organisms and spores are +destroyed. In addition to lactic acid ferments, there are large numbers +of others which develop in milk, changing the different compounds of +which milk is composed. In the processes of butter and cheese making, +these fermentation changes are controlled so as to develop the flavor +and secure the best grades of butter and cheese. + +108. Use of Preservatives in Milk.--In order to check fermentation, +boric acid, formalin, and other preservatives have been proposed. +Physiologists object to their use because the quantity required to +prevent fermentation is often sufficient to have a medicinal effect. +The tendency is to use excessive amounts, which may interfere with +normal digestion of the food. Milk that is cared for under the most +sanitary conditions has a higher dietetic value and is much to be +preferred to that which has been kept sweet by the use of preservatives. + +109. Condensed Milk is prepared by evaporating milk in vacuum pans +until it is reduced about one fourth in bulk, when it is sealed in cans, +and it will then keep sweet for a long time. Occasionally some cane +sugar is added to the evaporated product. When diluted, evaporated milk +has much the same composition as whole milk. When a can of condensed +milk has been opened, the same care should be exercised to prevent +fermentation as if it were fresh milk. + +110. Skim Milk differs in composition from whole milk in fat content. +When the fat is removed by the separator, there is often left less than +one tenth of a per cent. Skim milk has a much higher nutritive value +than is generally conceded, and wherever it can be procured at a +reasonable price it should be used in the dietary as a source of +protein. + +111. Cream ranges in fat content from 15 to 35 per cent. It is +generally preferred to whole milk, although it is not as well balanced a +food, because it is deficient in protein. Cream should contain at least +25 per cent of fat. + +112. Buttermilk is the product left after removal of the fat from +cream by churning. It has about the same amount of nutrients as skim +milk. The casein is in a slightly modified form due to the development +of lactic acid during the ripening of the cream, and on this account +buttermilk is more easily digested and assimilated by many individuals +than milk in other forms. The development of the acid generally reduces +the number of species of other than the lactic organisms, and these are +increased. + +113. Goat's Milk is somewhat richer in solids than cow's milk, +containing about one per cent more proteids, a little more fat, and less +sugar. When used as a substitute for human or cow's milk, it generally +needs to be slightly diluted, depending, however, upon the composition +of the individual sample. + +114. Koumiss is a fermented beverage made from milk by the use of +yeast to secure alcoholic fermentation. Koumiss contains about one per +cent each of lactic acid and alcohol, and the casein and other nutrients +are somewhat modified by the fermentation changes. Koumiss is generally +considered a non-alcoholic beverage possessing both food and dietetic +value. + +115. Prepared Milks.--Various preparations are made to resemble milk +in general composition. These are mechanical mixtures of sugar, fats, +and proteids. Milk sugar, casein, or malted proteids are generally the +materials employed in their preparation. Often the dried and pulverized +solids of skim milk are used. Many of the prepared milks are deficient +in fat. While they are not equal to cow's milk, their use is often made +necessary from force of circumstances. + +116. Human Milk is not as rich in solid matter as cow's milk. It +contains about the same amount of fat, one per cent more sugar, and one +per cent less proteids. In human milk nearly one half of the protein is +in the form of albumins, while in cow's milk there is about one fifth in +this form. The fat globules are much smaller than those of cow's milk. +In infant feeding it is often necessary to modify cow's milk by the +addition of water, cream, and milk sugar, so as to make it more nearly +resemble in composition human milk. + +[Illustration: FIG. 25.--APPARATUS USED IN TESTING MILK. + +1, pipette; 2, lactometer; 3, acid measure; 4, centrifuge; 5, test +bottle.] + +117. Adulteration of Milk.--Milk is not as extensively adulterated as +it was before the passage and enforcement of the numerous state and +municipal laws regulating its inspection and sale. The most frequent +forms of adulteration are addition of water and removal of cream. These +are readily detected from the specific gravity and fat content of the +milk. The specific gravity of milk is determined by means of the +lactometer, an instrument which sinks to a definite point in pure milk. +In watered milk it sinks to greater depth, depending upon the amount of +water added. The fat content of milk is readily and accurately +determined by the Babcock test, in which the fat is separated by +centrifugal action. For the detection of adulterated milk the student +is referred to Chapter VI, "Chemistry of Dairying," by Snyder. + + +BUTTER + +118. Composition.--Butter is made by the churning or agitation of +cream and is composed mainly of milk fats and water, together with +smaller amounts of ash, salt, casein, milk sugar, and lactic acid. +Average butter has the following composition: + + ============================ + |Per Cent + Water | 10.5 + Ash and salt | 2.5 + Casein and albumin | 1.0 + Fat | 86.0 + ============================ + +When butter contains an abnormal amount of water, it is considered +adulterated. According to act of Congress standard butter should not +contain over 16 per cent of water nor less than 82.5 per cent of fat. + +119. Digestibility of Butter.--Digestion experiments show that +practically all of the fat, 98 per cent, is digestible and available for +use by the body. Butter is valuable only for the production of heat and +energy. Alone, it is incapable of sustaining life, because it contains +no proteid material. It is usually one of the more expensive items of +food, but it is generally considered quite necessary in a ration.[5] It +has been suggested that it takes an important part mechanically in the +digestion of food. + +120. Adulteration of Butter.--In addition to containing an excess of +water, butter is adulterated in other ways. Old, stale butter is +occasionally melted, washed, salted, and reworked. This product is known +as renovated butter, and has poor keeping qualities. Frequently +preservatives are added to such butter to delay fermentation changes. +Oleomargarine and butterine are made by mixing vegetable and animal +fats.[40] Highly colored stearin, cotton-seed oil, and lard are the +usual materials from which oleomargarine is made. It has practically the +same composition, digestibility, and food value as butter. When sold +under its true name and not as butter, there is no objection, as it is a +valuable food and supplies heat and energy at less cost than butter. The +main objection to oleomargarine and butterine is that they are sold as +butter.[41] + +The coloring of butter is not generally looked upon as adulteration, for +butter naturally has a more or less yellow tinge. According to an act of +Congress, butter colors of a non-injurious character are allowed to be +used. + + +CHEESE + +121. General Composition.--Cheese, is made by the addition of rennet +to ripened milk, resulting in coagulation of the casein, which +mechanically combines with the fat. It differs from butter in +composition by containing, in addition to fat, casein and appreciable +amounts of mineral matter. The composition varies with the character of +the milk from which the cheese was made. Average milk produces cheese +containing a larger amount of fat than proteids, while cheese from +skimmed or partially skimmed milk is proportionally poorer in fat. +Ordinarily there is about 35 per cent of water, 33 per cent of fat, and +27 per cent of casein, and albumin or milk proteids, the remainder being +ash, salt, milk sugar, and lactic acid. Cheese is characterized by its +large percentage of both fat and protein, and has high food value. It +contains more fat and protein than any of the meats; in fact, there are +but few foods which have such liberal amounts of these nutrients as +cheese. + +The odor and flavor of cheese are due to workings of bacteria which +result in the production of aromatic compounds. The purity and condition +of the milk, as well as the method of manufacture and the kind of +ferment material used, determine largely the flavor and odor. Cheese is +generally allowed to undergo a ripening or curing process before it is +used as food. The changes resulting consist mainly in increased +solubility of the proteids, with the formation of a small amount of amid +and aromatic compounds.[42] + +122. Digestibility.--Cheese is popularly considered an indigestible +food, but extended experiments show that it is quite completely +digested, although in the case of some individuals not easily digested. +In general, about 95 per cent of the fat and 92 per cent and more of the +protein is digested, depending upon the general composition of the +cheese and the digestive capacity of the individual. As far as total +digestibility is concerned, there appears to be but little difference +between green and well-cured cheese. So far as ease of digestion is +concerned, it is probable that some difference exists. There is also but +little difference in digestibility resulting from the way in which milk +is made into cheese, the nutrients of Roquefort, Swiss, Camembert, and +Cheddar being about equally digestible.[13] The differences in odor and +taste are due to variations in kind and amount of bacterial action. When +combined with other foods, cheese may exercise a beneficial influence +upon digestion in the same way as noted from the use of several foods in +a ration. No material differences were observed in digestibility when +cheese was used in small amounts, as for condimental purposes, or when +used in large amounts to furnish nutrients. Artificial digestion +experiments show that cheese is more readily acted upon by the +pancreatic than by the gastric fluids, suggesting that cheese undergoes +intestinal rather than gastric digestion. It is possible this is the +reason that cheese is slow of digestion in the case of some individuals. + +123. Use in the Dietary.--Cheese should be used in the dietary +regularly and in reasonable amounts, rather than irregularly and then in +large amounts. Cheese is not a luxury, but ordinarily it is one of the +cheapest and most nutritious of human foods. A pound of cheese costing +15 cents contains about a quarter of a pound of protein and a third of a +pound of fat; at the same price, beef yields only about half as much fat +and less protein. Cheese at 18 cents per pound furnishes more available +nutrients and energy than beef at 12 cents per pound. In the dietary of +European armies, cheese to a great extent takes the place of beef. See +Chapter XVI. + +124. Cottage Cheese is made by coagulating milk and preparing the curd +by mixing with it cream or melted butter and salt or sugar as desired. +When milk can be procured at little cost, cottage cheese is one of the +cheapest and most valuable foods.[43] + +125. Different Kinds of Cheese.--By the use of different kinds of +ferments and variations in the process of manufacture different types or +kinds of cheese are made, as Roquefort, Swiss, Edam, Stilton, Camembert, +etc. In the manufacture of Roquefort cheese, which is made from goats' +and ewes' milk, bread is added and the cheese is cured in caves, +resulting in the formation of a green mold which penetrates the cheese +mass, and produces characteristic odor and flavor. Stilton is an English +soft, rich cheese of mild flavor, made from milk to which cream is +usually added. It is allowed to undergo an extended process of ripening, +often resulting in the formation of bluish green threads of fungus. +Limburger owes its characteristic odor and flavor to the action of +special ferment bodies which carry on the ripening process. Neufchatel +is a soft cheese made from sweet milk to which the rennet is added at a +high temperature. After pressing, it is kneaded and worked, and then put +into packages and covered with tin foil. + +126. Adulteration of Cheese.--The most common forms of adulteration +are the manufacture of skim-milk cheese by the removal of the fat from +the milk, and substitution of cheaper and foreign fats, making a product +known as filled cheese. When not labeled whole milk cheese, or sold as +such, there is no objection to skim-milk cheese. It has a high food +value and is often a cheap source of protein. The manufacture of filled +cheese is now regulated by the national government, and all such cheese +must pay a special tax and be properly labeled. As a result, the amount +of filled cheese upon the market has very greatly decreased, and cheese +is now less adulterated than in former years. The national dairy law +allows the use of coloring matter of a harmless nature in the +manufacture of cheese. + +127. Dairy Products in the Dietary.--The nutrients in milk are +produced at less expense for grain and forage than the nutrients in +beef, hence from a pecuniary point of view, dairy products, as milk and +cheese, have the advantage. In the case of butter, however, the cost +usually exceeds that of meat. In older agricultural regions, where the +cost of beef production reaches the maximum, dairying is generally +resorted to, as it yields larger financial returns, and as a result more +cheese and less beef are used in the dietary. As the cost of meats is +enhanced, dairy products, as cheese, naturally take their place. + + + + +CHAPTER VIII + +MEATS AND ANIMAL FOOD PRODUCTS + + +128. General Composition.--Animal tissue is composed of the same +classes of compounds as plant tissue. In each, water makes up a large +portion of the weight, and the dry matter is composed of nitrogenous and +non-nitrogenous compounds, and ash or mineral matter. Plants and animals +differ in composition not so much as to the kinds of compounds, although +there are differences, but more in the percentage amounts of these +compounds. In plants, with the exception of the legumes, the protein +rarely exceeds 14 per cent, and in many vegetable foods, when prepared +for the table, there is less than 2 per cent. In meats the protein +ranges from 15 to 20 per cent. The non-nitrogenous compounds of plants +are present mainly in the form of starch, sugar, and cellulose, while in +animal bodies there are only traces of carbohydrates, but large amounts +of fat. Fat is the chief non-nitrogenous compound of meats; it ranges +between quite wide limits, depending upon kind, age, and general +condition of the animal. Meats contain the same general classes of +proteins as the vegetable foods; in each the proteins are made up of +albumins, glubulins, albuminates, peptone-like bodies, and insoluble +proteids. The larger portion of the protein of meats and cereals is in +insoluble forms. The meat juices, which contain the soluble portion of +the proteins, constitute less than 5 percent of the nitrogenous +compounds. Meats contain less amid substances than plants, in which the +amids are produced from ammonium compounds and are supposed to be +intermediate products in the formation of proteids, while in the animal +body they are derived from the proteids supplied in the food and, it is +generally believed, cannot form proteids. Albuminoids make up the +connective tissue, hair, and skin, and are more abundant in animal than +in plant tissue. One of the chief albuminoids is gelatine. Both plant +and animal foods undergo bacterial changes resulting in the production +of alkaloidal bodies known as ptomaines, of which there are a large +number. These are poisonous and are what cause putrid and stale meat to +be unwholesome. The protein in meat differs little in general +composition from that of vegetable origin; differences in structure and +cleavage products between the two are, however, noticeable. + +[Illustration: FIG. 26.--MEAT AND EXTRACTIVE SUBSTANCES.] + +While meats from different kinds of animals have somewhat the same +general composition, they differ in physical properties, and also in the +nature of the various nutrients. For example, pork contains less protein +than beef, but the protein of pork is materially different from that of +beef, as a larger portion is in the form of soluble proteids, while in +beef more is present in an insoluble form. Not only are differences in +the percentage of individual proteins noticeable, but there are equally +as great differences in the fats. As for example: some of the meats have +a larger proportion of the fat as stearin than do others. Hence meats +differ in texture and taste more than in nutritive value, due to the +variations in the percentage of the different proteins, fats, and +extractive material, rather than to differences in the total amounts of +these compounds. The taste and flavor of meat is to a large extent +influenced by the amount of extractive material. + +While the nutrients of meats are divided into classes, as proteins and +fats, there are a large number of separate compounds which make up each +of the individual classes, and there are also small amounts of +compounds which are not included in these groups. + +[Illustration: FIG. 27.--STANDARD CUTS OF BEEF. + +(From Office of Experiment Station Bulletin.)] + +129. Beef.--About one half of the weight of beef is water; the lean +meat contains a much larger amount than the fat. As a rule, the parts of +the animal that contain the most fat contain the least water. In some +meats there is considerable refuse, 25 to 30 per cent. In average meat +about 12 per cent of the butcher's weight is refuse and non-edible +parts.[44] A pound of average butcher's meat is about one half water, +and over 10 per cent waste and refuse, which leaves less than 40 per +cent fat and protein. Meat is generally considered to have a high +nutritive value, due to the comparatively large amounts of fat and +protein. Beef contains more protein than any vegetable food, except the +legumes, and from 1 to 1.5 per cent mineral matter, exclusive of bone. +Some of the mineral matter is chemically united with the protein and +other compounds. While figures are given for average composition of +beef, it is to be noted that wide variations are frequently to be met +with, some samples containing a much larger amount of waste and +trimmings than others, and this influences the percent of the nutritive +substances. In making calculations of nutrients consumed, as in dietary +studies, the figures for average composition of meat should be used only +in cases where the samples do not contain an excess either of fat or +trimmings.[45] When very lean, there is often a large amount of refuse, +and the meat contains less dry matter and is of poorer flavor than from +animals in prime condition. In the case of very fat animals, a large +amount of waste results, and the flavor is sometimes impaired. + +130. Veal differs from beef in containing a smaller amount of dry +matter, richer in protein, but poorer in fat. Animals differ in +composition at different stages of growth in much the same way as +plants. In the earlier stages protein predominates in the plant tissue, +while later the carbohydrates are added in larger amounts, reducing the +percentage content of protein. In animals the same is noticeable. Young +animals are, pound for pound, richer in protein than old animals. While +in the case of vegetables the increase in size, or rotundity, is due to +starch and carbohydrates, in animals it is due to the addition of fat. +But plants, like animals, observe the same general laws as to changes in +composition at different stages of growth. + +[Illustration: FIG. 28.--STANDARD CUTS OF MUTTON. + +(From Office of Experiment Station Bulletin.)] + +131. Mutton.--There is about the same amount of refuse matter in mutton +as in beef. In a side of mutton about 19 percent: are trimmings and +waste, and in a side of beef 18.5 per cent. Mutton, as a rule, contains +a little more fat and dry matter than beef, and somewhat less protein. A +side of beef, as purchased, contains about 50 per cent of water, 14.5 +per cent protein, and 16.8 per cent of fat, while a side of mutton, as +purchased, contains 42.9 per cent water, 12.5 per cent protein, and 24.7 +per cent fat. A pound of beef yields a smaller number of calories by 25 +per cent than a pound of mutton. At the same price per pound more +nutrients can be purchased as mutton than as beef. The differences in +composition between lamb and mutton are similar to those between veal +and beef; viz. a larger amount of water and protein and a smaller amount +of fat in the same weight of the young animals. Differences in +composition between the various cuts of lamb are noticeable. The leg +contains the least fat and the most protein, while the chuck is richest +in fat and poorest in protein. As in the case of beef, many of the +cheaper cuts contain as much or more nutrients than the more expensive +cuts. They are not, however, as palatable and differ as to toughness and +other physical characteristics. + +[Illustration: FIG. 29.--STANDARD CUTS OF PORK. + +(From Office of Experiment Station Bulletin.)] + +132. Pork is characterized by a high per cent of fat and a +comparatively low per cent of protein. It is generally richest in fat of +any of the meats. The per cent of water varies with the fatness of the +animal; in very fat animals there is a smaller amount, while lean +animals contain more. In lean salt pork there is about 20 per cent +water, and in fat salt pork about 7 per cent. There is less refuse and +waste in pork than in either beef or mutton. Ham contains from 14 to 15 +per cent of refuse, and bacon about 7 per cent. Bacon has nearly twice +as much fat and a smaller amount of protein than ham. A pound of bacon, +as purchased, will yield nearly twice as much energy or fuel value as a +pound of ham. Digestion experiments show that bacon is quite readily and +completely digested and is often a cheaper source of fat and protein +than other meats. There is about three times as much fat in bacon as in +beef. When prepared for the table bacon contains, from 40 to 50 per cent +of fat. A pound of high grade, lean bacon furnishes from 0.1 to 0.3 of a +pound of digestible protein and from 0.4 to 0.6 of a pound of digestible +fat, which is about two thirds as much fat as is found in butter. Bacon +contains nearly as much digestible protein as other meats and from two +to three times as much fat, making it, at the same price per pound, a +cheaper food than other meats. In salt pork there is from 60 to 85 per +cent of fat, and less protein than in bacon. The protein and fat of pork +differ from those in beef not only in percentage amounts, but also in +the nature of the individual proteins and fats. The composition of pork +varies with the nature of the food that is consumed by the animal. +Experiments show that it is possible by judicious feeding in the early +stages of growth to produce pork with the maximum of lean meat and the +minimum of fat. After the animal has passed a certain period, it is not +possible by feeding to materially influence the percentage of nutrients +in the meat. The flavor, too, of pork, as of other meats, is dependent +largely upon the nature of the food the animal consumes. When there is a +scant amount of available protein in the ration, the meat is dry, nearly +tasteless, and contains less of the soluble nitrogenous compounds which +impart flavor and individuality. + +133. Lard is prepared from the fat of swine, and is separated from +associated tissue by the action of heat. A large amount of fat is found +lining the back of the abdominal cavity, and this is known as leaf lard. +Slight differences are noticeable in the composition and quality of lard +made from different parts of the hog. Leaf lard is usually considered +the best. Lard is composed of the three fats, olein, stearin, and +palmatin, and has a number of characteristic physical properties, as +specific gravity, melting point, iodine absorption number, as well as +behavior with various reagents, and these enable the mixing of other +fats with lard to be readily detected. Lard is used in the preparation +of oleomargarine, and it is also combined with various vegetable oils, +as cotton-seed oil, in the making of imitation or compound lards.[46] +Lard substitutes differ little in general composition from pure lard, +except in the structure of the crystals and the percentage of the +various individual fats. + +134. Texture and Toughness of Meats.--In discussing the texture of +meats, Professor Woods states:[45] + + "Whether meats are tough or tender depends upon two things: the + character of the walls of the muscle tubes and the character of the + connective tissues which bind the tubes and muscles together. In + young and well-nourished animals the tube walls are thin and + delicate, and the connective tissue is small in amount. As the + animals grow older or are made to work (and this is particularly + true in the case of poorly nourished animals), the walls of the + muscle tubes and the connective tissues become thick and hard. This + is the reason why the flesh of young, well-fed animals is tender + and easily masticated, while the flesh of old, hard-worked, or + poorly fed animals is often so tough that prolonged boiling or + roasting seems to have but little effect on it. + + "After slaughtering, meats undergo marked changes in texture. These + changes can be grouped under three classes or stages. In the first + stage, when the meat is just slaughtered, the flesh is soft, juicy, + and quite tender. In the next stage the flesh stiffens and the meat + becomes hard and tough. This condition is known as _rigor mortis,_ + and continues until the third stage, when the first changes of + decomposition set in. In hot climates the meat is commonly eaten in + either the first or second stage. In cold climates it is seldom + eaten before the second stage, and generally, in order to lessen + the toughness, it is allowed to enter the third stage, when it + becomes soft and tender, and acquires added flavor. The softening + is due in part to the formation of lactic acid, which acts upon the + connective tissue. The same effect may be produced, though more + rapidly, by macerating the meat with weak vinegar. Meat is + sometimes made tender by cutting the flesh into thin slices and + pounding it across the cut ends until the fibers are broken." + +135. Influence of Cooking upon the Composition of Meats.[47]--It is +believed by many that losses are prevented and the nutritive value +conserved when, in the cooking of meat, it is placed directly into +boiling water rather than into cold water and then brought to the +boiling point and cooked. Extensive experiments have been made by Dr. +Grindley in regard to this and other points connected with the cooking +of meats, and in general it was found that the temperature of the water +in which the meat was placed made little difference in its nutritive +value or the amount of material extracted. It was found that by both +methods there was dissolved 2.3 percent of the protein matter, 1 percent +of the nitrogenous extractives, 1.6 per cent of non-nitrogenous +material, and 0.8 per cent of ash, of the raw meat, which was equivalent +to about 13 per cent of the total proteid material and 81 percent of the +ash. The cold water extract contained bodies coagulated by heat. Cold +water did not extract any of the fat, but during the process of cooking, +appreciable amounts were lost mechanically. Cooked meats were found to +be less soluble in cold water than raw meats. During the process of +boiling, meat shrinks in weight about 40 or 45 per cent, depending +mainly upon the size of the pieces and the content of fat. The loss in +weight is practically a loss of water, and the loss of nutrients, all +told, amounts to about 4 per cent, or more, depending upon the +mechanical loss.[48] But slight differences were found in the +composition of the meats cooked three and five hour periods. + + "Careful study in this laboratory has shown that when meat is + cooked in water at 80 deg. to 85 deg. C., placing meat in hot or + cold water at the start has little effect on the amount of + nutrients in the meat which passes into the broth. The meat was + in the form of cubes, one to two inches, and in pieces weighing + from one to two pounds. + + "It is commonly supposed that when meat is plunged into boiling + water, the albumin coagulates and forms a crust, which prevents the + escape of nutritive materials into the broth. It is also believed + that if a rich broth is desired, to be used either as a soup or + with the meat as a stew, it is more desirable to place the meat in + cold water at the start. From the results of these experiments, + however, it is evident that, under these conditions, there can be + little advantage in using hot or cold water at the beginning. When + meats were cooked by dry heat, as in roasting, a larger amount of + nutrients was rendered soluble in water than during boiling. The + losses of nutrients were much smaller when meats were cooked by dry + heat than when cooked in water, being on the average, water 35 per + cent, nitrogenous extractives 9 per cent, non-nitrogenous + extractives 17 per cent, fat 7 per cent, ash 12 per cent, and a + small loss of protein." + +The nutrients in the broth of the meat started in hot water amounted to +about 1 per cent of protein, 1 per cent of fat, and O.5 per cent of +ash, the amount of nutrients being directly proportional to the length +of time and temperature of the cooking. In general, the larger the +pieces, the smaller the losses. Beef that has been used in the +preparation of beef tea loses its extractive materials, which impart +taste and flavor, but there is only a small loss of actual nutritive +value. Clear meat broth contains little nutriment--less than unfiltered +broth. Most of the nitrogenous material of the broth is in the form of +creatin, sarkin, and xanthin, nitrogenous extractives or amid substances +having a much lower food value than proteids. Experiments show that some +of these extractives have physiological properties slightly stimulating +in their action, and it is believed the stimulating effect of a meat +diet is in part due to these.[49] They are valuable principally for +imparting taste and flavor, and cannot be regarded as nutrients. The +variations in taste and flavor of meats from different sources are due +largely to differences in extractive material. + + "In general, the various methods of cooking materially modify the + appearance, texture, and flavor of meat, and hence its + palatability, but have little effect on total nutritive value. + Whether it be cooked in hot water, as in boiling or stewing, or by + dry heat, as in roasting, broiling, or frying, meat of all kinds + has a high food value, when judged by the kind and amount of + nutrient ingredients which are present." [50] + +Beef extracts of commerce contain about 50 per cent of extractive +matters, as amids, together with smaller amounts of soluble proteids; +ash, mainly added salt, is also present in liberal amounts (20 per +cent). Beef extracts have condimental value imparting taste and flavor, +which make them useful for soup stocks, but they furnish little in the +way of nutritive substance. + +136. Miscellaneous Meat Products.--By combining different parts of the +same animal, or different meats, a large number of products known as +sausage are made. These vary in composition with the ingredients used. +In general, they are richer in fat than beef and contain about the same +amount of protein. Potato flour and flour from cereals are sometimes +used in their preparations, but the presence of any material amount, +unless so stated on the package, is considered an adulterant. + +Pickled meats are prepared by the use of condiments, as salt, sugar, +vinegar, and saltpeter. During the smoking and curing of meats, no +appreciable losses of nutrients occur.[51] The smoke acts as a +preservative, and imparts condimental properties. Saltpeter (potassium +nitrate) has been used from earliest times in the preparation of meats; +it preserves color and delays fermentation changes. When used in +moderate amounts it cannot be regarded as a preservative or injurious to +health. Excessive amounts, however, are objectionable. Smoked meats, +prepared with or without saltpeter, give appreciable reactions for +nitrites, compounds formed during combustion of the wood by which the +meat was smoked. Many vegetables contain naturally much larger amounts +of nitrates, taken from the soil as food, than meat that has been +preserved with saltpeter.[52] + +137. Poultry.--The refuse and waste from chickens, as purchased on the +market, ranges from 15 to 30 per cent. The fat content is much lower +than in turkeys or ducks, the largest amount being found in geese. The +edible portion of all fowls is rich in protein, particularly the dark +meat, and the food value is about equal to that of meat in general. When +it is desired to secure a large amount of protein with but little fat, +chicken supplies this, perhaps, better than any other animal food. A +difference is observed in the composition of the meat of young and old +fowls similar to that between beef and veal. The physical composition +and, to a slight extent, the solubility of the proteids are altered by +prolonged cold storage, the difference being noticeable mainly in the +appearance of the connective tissue of the muscles. In discussing +poultry as food, Langworthy states:[53] + + "A good, fresh bird shows a well-rounded form, with neat, compact + legs, and no sharp, bony angles on the breast, indicating a lack of + tender white meat. The skin should be a clear color (yellow being + preferred in the American market) and free from blotches and pin + feathers; if it looks tight and drawn, the bird has probably been + scalded before being plucked. The flesh should be neither flabby + nor stiff, but should give evenly and gently when pressed by the + finger." + +138. Fish.--From 30 to 60 per cent of the weight of fresh fish is +refuse. The edible portion contains from 35 to 50 per cent, and in some +cases more, of water. The dry matter is rich in protein; richer than +many meats. The nutrients in fish range between comparatively wide +limits, the protein in some cases being as low as 6 per cent, in +flounder, and in others as high as 30 per cent, in dried codfish. The +amount of fat, except in a few cases, as salmon and trout, is small. +Salmon is the richest in fat of any of the fishes. When salted and +preserved, the proportion of water is lessened and that of the nutrients +is increased. Fish can take the place of meat in the dietary, but it is +necessary to add a larger amount of fat to the ration because of the +deficiency of most fish in this ingredient. Fish has about the same +digestibility as meats. It is believed by many to be valuable because it +supplies a large amount of available phosphates. Analyses, however, show +that the flesh of fish contains no more phosphorus compounds than meats +in general, and its food value is due to protein rather than to +phosphates.[54] + +Fish appears to be as completely and easily digested as meats. +Differences in flavor, taste, and palatability are due to small amounts +of flavors and extractive materials, varying according to the food +consumed by the fish and the conditions under which they lived. The +flesh of fish decays more readily than that of other meats and produces +ptomaines, or toxic substances, which are the result of fermentation +changes usually associated with putrefaction. Cases of poisoning from +eating unsound fish are not infrequent.[55] + +Shellfish have about the same general composition as fish. In clams +there is a larger amount of dry matter than in oysters, which contain +about 12 per cent, half of which is protein. When placed in fresh water, +the oyster increases in size and undergoes the process known as +"fattening." Oftentimes impure water is used for this purpose, which +makes the eating of raw oysters a questionable practice from a sanitary +point of view, as the water in which they are floated often contains +disease-producing germs, as typhoid. During the process of fattening, +although the oyster increases in size and weight, it decreases in +percentage of nutrients. In discussing the composition of oysters, +Atwater states:[7] + + "They come nearer to milk than almost any other food material as + regards both the amounts and relative proportions of nutrients." + +139. Eggs, General Composition.--Eggs are a type of concentrated +nitrogenous food. About 75 per cent (shell removed) is water, about one +third is yolk, and a little over 50 per cent is albumin or white. The +shell makes up from 10 to 12 per cent of the weight. The yolk and white +differ widely in composition. The yolk contains a much larger per cent +of solids than the white, and is rich in both fat and protein, from a +third to a half of the weight being fat. The white has about the same +amount of water, 88 per cent, as average milk, but, unlike milk, the dry +matter is mainly albumin. The entire egg (edible portion) contains +about equal parts of fat and protein; 12 to 13 per cent of each and an +appreciably large amount of ash or mineral matter,--from 0.8 to 1 per +cent, consisting mainly of phosphates associated with the albumin. There +is no material difference in chemical composition between white and dark +shelled eggs, or between eggs with different colored yolks. It is simply +a question of coloring matter. The egg is influenced to an appreciable +extent by feed and general care of the fowls. The egg and the potato +contain about the same amount of water. They are, however, distinct +types of food, the potato being largely composed of carbohydrates and +the egg of protein and fat. Eggs resemble meat somewhat in general +composition, although they contain rather less of protein and fat. When +eggs are boiled there is a loss of weight due to elimination of water; +otherwise the composition is unaltered, the coagulation of the albumin, +as stated in Chapter I, consisting simply in a rearrangement of the +atoms of the molecule. The egg is particularly valuable in the dietary +of the convalescent, when it is desired to secure the maximum amount of +phosphorus in organic combination. + +[Illustration: FIG. 30.--GRAPHIC COMPOSITION OF AN EGG.] + +The flavor of eggs is in part due to the food supplied to the fowls, as +well as the age of the egg. Experiments show that onions and some other +vegetables, when fed to fowls, impart odors and taste to the eggs. The +keeping qualities of eggs are also dependent upon the food supplied. In +experiments at the Cornell Experiment Station, when hens were fed on a +narrow, nitrogenous ration, a large number of eggs were produced +containing the minimum amount of solid matter and of poor keeping +quality, while a larger sized egg of better keeping quality was obtained +when a variety of foods, nitrogenous and non-nitrogenous, was supplied. + +140. Digestibility of Eggs.--Digestion experiments show that there is +but little difference in the digestibility of eggs cooked in different +ways. A noticeable difference, however, is observed in the rapidity with +which the albumin and proteids are dissolved in a pepsin solution. In +general, it was found that, when the albumin was coagulated at a +temperature of 180 deg., it was more rapidly and completely dissolved in +the pepsin than when coagulated at a temperature of 212 deg. When eggs +were cooked at a temperature of 212 deg., the hard-boiled eggs appeared to +be slightly more digestible than the soft-boiled eggs, but the digestion +was not as complete as when the cooking was done at a temperature of +180 deg.; then no difference in digestibility was found between eggs +cooked for a short or a long time. The egg is one of the most completely +digested of all foods, practically all the protein and fat being +absorbed and available to the body. Langworthy, in discussing +Jorissenne's investigations on the digestibility of eggs, states:[53] + + "The yolk of raw, soft-boiled, and hard-boiled eggs is equally + digestible. The white of soft-boiled eggs, being semi-liquid, + offers little more resistance to the digestive juices than raw + white. The white of a hard-boiled egg is not generally very + thoroughly masticated. Unless finely divided, it offers more + resistance to the digestive juices than the fluid or semi-fluid + white, and undigested particles may remain in the digestive tract + many days and decompose. From this deduction it is obvious that + thorough mastication is a matter of importance. Provided + mastication is thorough, marked differences in the completeness of + digestion of the three sorts of eggs, in the opinion of the writer + cited, will not be found." + +141. Use of Eggs in the Dietary.--When eggs are at the same price per +dozen as meat is per pound, they furnish a larger amount of nutrients. +In general, a dozen eggs have a little higher food value than a pound of +meat. Eggs are usually a cheaper source of food because a smaller amount +is served than of meat. When eggs are 25 cents per dozen, the cost of +ten eggs for a family of five is less than that of a pound or a pound +and a quarter of beef at 22 cents per pound. The meat, however, would +furnish the larger amount of nutrients. Eggs are valuable, too, in the +dietary because they are frequently combined with flour, cereal +products, and vegetables, which contain a large amount of starch, and +some of which contain small amounts of protein. This combination +furnishes a balanced ration, as well as secures palatability and good +mechanical combination of the foods. Eggs in combination with flour, +sugar, butter, and other materials have equally as great a value as when +used alone and as a substitute for meat. + +Eggs vary in weight from 17.5 to 28 ounces, and more per dozen. They +should be purchased and sold by weight. When stored, eggs lose weight. +The egg cannot be considered as entirely germ proof, and care is +necessary in its handling and use, the same as with other food articles. +The cause of the spoiling of eggs is due largely to exterior bacterial +infection. + + +CANNED MEATS + +142. General Composition.--Canned meats differ but little in +composition from fresh meats. Usually during the process of cooking and +canning there is a slight increase in the amount of dry matter, but the +relative proportion of protein and fat is about the same as in fresh +meat. It is frequently stated that the less salable parts are used in +the preparation of canned meats, as it is possible by cooking and the +addition of condiments to conceal the inferior physical properties. As +to the accuracy of these statements, the author is unable to say. The +shrinkage or loss in weight during canning amounts to from 30 to 40 per +cent. The liquids in which the cooking and parboiling are done are +sometimes used in the preparation of beef extracts. Salt, saltpeter, and +condiments are generally added during the canning process. Saltpeter is +used, as it assists in retaining the natural color and prevents some +objectionable fermentation changes. In moderate amounts it is not +generally considered an adulterant. An extensive examination by Wiley +and Bigelow of packing-house products and preserved meats showed that of +the latter only a small amount contained objectionable preservatives. +The authors, after an extended investigation, reported favorably upon +their composition and sanitary value, saying they found "so little to +criticise and so much to commend in these necessary products." In this +bulletin they do not classify saltpeter as an adulterant.[51] + +Where fresh meats cannot be secured, canned meats are often +indispensable. Usually the nutrients of canned meats cost more than +those of fresh meats, and in their use as food much care should be +exercised to prevent contamination after opening the cans. Occasionally +the meat contains ferment materials that have not been entirely +destroyed during cooking, and these, when the cans are stored in warm +places, develop and cause deleterious changes to occur. Consequently +canned meats should be stored at a low temperature. By recent +congressional act, these preparations are now made under the +supervision of government inspectors. All diseased animals are +rejected, and the sanitary conditions under which the meat is prepared +have been greatly improved. Formerly, the most frequent forms of +adulteration were substitution of one meat for another, as the mixing of +veal with chicken, and the use of preservatives, as borax and sulphites. +While the cost of the nutrients in canned meats is generally much higher +than in fresh meats, the latter are not always easily obtained, or +capable of being kept for any length of time, and hence canned meats are +often indispensable. + + + + +CHAPTER IX + +CEREALS + + +143. Preparation and Cost of Cereals.--The grains used in the +preparation of cereal foods are wheat, oats, corn, rice, and, to a less +extent, barley and rye. For some of these the entire cleaned grain is +ground or pulverized, while for others the bran and germ are first +removed. In order to improve their keeping qualities, they are often +sterilized before being put up in sealed packages. Special treatment, as +steaming or malting, is sometimes given to impart palatability and to +lessen the time required for cooking. As a class, the cereal foods are +clean, nutritious, and free from adulteration. Extravagant claims are +sometimes made as to their food value, and frequently excessive prices +are charged, out of proportion to the cost of the nutrients in the raw +material. Within recent years the number of cereal preparations has +greatly increased, due to improvements and variations in the methods of +manufacture.[56] + +Cereal foods are less expensive than meats and the various animal food +products. They contain no refuse, are easily prepared for the table, and +may be kept without appreciable deterioration. Some of the +ready--to-eat brands are cooked, dried, and crushed, and sugar, +glucose, salt, and various condimental materials added to impart taste. +Others contain malt, or are subjected to a malting or germinating +process to develop the soluble carbohydrates, and such foods are +sometimes called predigested. It is believed that the cereals are being +more extensively used in the dietary, which is desirable both from an +economic and a nutritive point of view. Special care is necessary in the +cooking and preparation of cereals for the table, in order to develop +flavor and bring about hydration and rupturing of the tissues, as +explained in Chapter II. + +144. Corn Preparations.--Corn or maize is characterized by a high +percent of fat and starch, and, compared with wheat and oats, a low +content of protein.[57] Removal of the bran and germ lessens the per +cent of fat. The germ is removed principally because it imparts poor +keeping qualities. Many of the corn breakfast foods contain 1 per cent +or less of fat and from 8 to 9 per cent of protein. Coarsely ground corn +foods are not as completely digested and assimilated as those more +finely ground. As in the case of wheat products, the presence of the +bran and germ appears to prevent the more complete absorption of the +nutrients. Finely ground corn meal compares favorably in digestibility +with wheat flour. Corn flour is prepared by removal of the bran and germ +and granulation of the more starchy portions of the kernel, and has +better keeping qualities than corn meal from which the bran and germ +have not been so completely removed. At times corn flour has been +sufficiently low in price to permit its use for the adulteration of +wheat flour. The mixing of corn and wheat flours, however, is prohibited +by law unless the product is so labeled. When combined with wheat flour, +corn bread and various other articles of food are prepared, but used +alone corn flour is not suitable for bread making, because its gluten +lacks the binding properties imparted to wheat flour by the gliadin. It +is essential that corn be used with foods of high protein content so as +to make a balanced ration; for when it forms a large part of the +dietary, the ration is apt to be deficient in protein. In a mixed +dietary, corn is one of the cheapest and best cereals that can be used. +Too frequently, however, excessive prices are charged for corn +preparations that contain no more nutrients than ordinary corn meal. +There is no difference between yellow and white corn meal so far as +nutritive value is concerned. + +[Illustration: FIG. 31.--CORN STARCH.] + +145. Oat Preparations are characterized by large amounts of both +protein and fat. Because of the removal of the hulls, they contain more +protein than the original grain. The oat preparations differ little in +chemical composition. They all have about 16 per cent of protein, 7 per +cent of fat, and 65 per cent of starch, and are richer in ash or mineral +matter than other cereals. The main difference is in method of +preparation and mechanical composition. Some are partially cooked and +then dried. Those costing 7 cents or more per pound do not contain any +greater amount of nutritive substance than those purchased in bulk at +about half the price. At one time it was believed that oats contained a +special alkaloid having a stimulating effect when fed to animals. Recent +investigations, however, show that there is no alkaloidal material in +oats, and whatever stimulating effect they may have results from the +nutrients they contain. Occasionally there is an appreciable amount of +cellulose, or fiber, left in the oat preparations, due to imperfect +milling. This noticeably lowers the digestibility. Oatmeal requires much +longer and more thorough cooking than many other cereals, and it is +frequently used as food when not well prepared. Digestion experiments +show that when oatmeal is cooked for four hours or more, it is more +readily acted upon by the diastase ferment and digested in a shorter +time than oatmeal cooked only a half hour.[5] Oatmeal is one of the +cheapest sources from which protein is obtained, and when well cooked it +can advantageously form an essential part of the ration. Unless +thoroughly cooked, the oat preparations do not appear to be quite so +completely or easily digested as some of the other cereals. + +[Illustration: FIG. 32.--OAT STARCH GRANULES.] + +[Illustration: FIG. 33.--WHEAT STARCH GRAINS.] + +146. Wheat Preparations differ in chemical composition more than those +from oats or corn, because wheat is prepared in a greater variety of +ways. They are made either from the entire kernel, including the bran +and germ, or from special parts, as the granular middlings, as in the +case of some of the breakfast foods, and a few are made into a dough and +baked, then dried and toasted. Some special flours are advertised as +composed largely of gluten, but only those that have been prepared by +washing out the starch are entitled to be classed as gluten flours.[58] +For the food of persons suffering from diabetes mellitus physicians +advise the use of flour low in starch, and this can be made by washing +and thus removing a portion of the starch from wheat flour, as directed +in Experiment No. 30. The glutinous residue is then used for preparing +articles of food. Analyses of some of the so-called gluten flours show +that they contain no more gluten than ordinary flour, particularly the +low grades. A number of wheat breakfast foods are prepared by +sterilizing the flour middlings obtained after removal of the bran and +germ. These middlings are the same stock or material from which the +patent grades of flour are made, and they differ from wheat flour only +in mechanical structure and size of the particles. Where granular wheat +middlings can be secured in bulk at the same price as flour they furnish +a valuable and cheap cereal breakfast food. + +As to the digestibility and food value, the wheat breakfast foods have +practically the same as graham, entire wheat, or ordinary patent flour, +depending upon the stock which they contain. Those with large amounts of +bran and germ are not as completely digested as when these parts of the +kernel are not included. Wheat preparations, next to oats, have the most +protein of any of the cereal foods. Occasionally they are prepared from +wheats low in gluten and not suitable for bread-making purposes. When +purchased in bulk the wheat preparations are among the cheapest foods +that can be used in the dietary.[56] + +[Illustration: FIG. 34.--BARLEY STARCH.] + +147. Barley Preparations are not so extensively used as wheat, oats, +and corn. Barley contains a little more protein than corn, but not quite +so much as wheat; otherwise it is quite similar to wheat in general +composition. Sometimes in the preparation of breakfast foods barley meal +is mixed with wheat or corn. Barley is supposed to be more readily +digested than some of the other cereals, because of the presence of +larger amounts of active ferment bodies, and it is frequently used for +making an extract known as "barley water," which, although it contains +very little nutritive value, as less than one per cent of the weight of +the barley is rendered soluble, is useful in its soothing influence and +mechanical action upon the mucous membrane of the digestive tract. + +[Illustration: FIG. 35.--RICE STARCH.] + +148. Rice Preparations.--Rice varies somewhat in composition, but +usually contains a slightly lower percentage of protein than corn and +also a smaller amount of fat. It is particularly rich in starch, and has +the least ash or mineral matter of any of the cereals. In order to make +a balanced ration, rice should be supplemented with legumes and other +foods rich in proteids. It is a valuable grain, but when used alone it +is deficient in protein. Rice is digested with moderate ease, but is not +as completely absorbed by the body as other cereals, particularly those +prepared by fine grinding or pulverization. Of late years rice culture +has been extensively introduced into some of the southern states, and +the domestic rice seems to have slightly higher protein content than the +imported. Rice contains less protein than other cereals, and the starch +grain is of different construction. Rice does not require such prolonged +cooking as oatmeal; it needs, however, to be thoroughly cooked. + +149. Predigested Foods.[56] + + "It is questionable whether it would be of advantage to a healthy + person to have his food artificially digested. The body under + normal conditions is well adapted to utilize such foods as the + ordinary mixed diet provides, among them the carbohydrates from the + cereals. Moreover, it is generally believed that for the digestive + organs, as for all others of the body, the amount of exercise they + are normally fitted to perform is an advantage rather than the + reverse. It has been said that 'a well man has no more need of + predigested food than a sound man has for crutches.' If the + digestive organs are out of order, it may be well to save them + work, but troubles of digestion are often very complicated affairs, + and the average person rarely has the knowledge needed to prescribe + for himself. In general, those who are well should do their own + work of digestion, and those who are ill should consult a competent + physician."--WOODS AND SNYDER. + +150. The Value of Cereals in the Dietary.--Cereals are valuable in the +dietary because of the starch and protein they supply, and the heat and +energy they yield. They are among the most inexpensive of foods and, +when properly prepared, have a high degree of palatability; then, too, +they are capable of being blended in various ways with other foods. Some +are valuable for their mechanical action in digestion, rather than for +any large amount of nutrients. They do not furnish the quantity of +mineral matter and valuable phosphates that is popularly supposed. They +all contain from 0.5 to 1.5 percent of mineral matter, of which about +one third is phosphoric anhydrid. In discussing the phosphate content of +food, Hammersten states:[59] + + "Very little is known in regard to the need of phosphates or + phosphoric acid.... The extent of this need is most difficult to + determine, as the body shows a strong tendency, when increased + amounts of phosphorus are introduced, to retain more than is + necessary. The need of phosphates is relatively smaller in adults + than in young developing animals." + +In the coarser cereals, which include the bran and germ, there is the +maximum amount of mineral matter, but, as in the case of graham bread, +it is not as completely digested and absorbed by the body as the more +finely granulated products which contain less. The kind of cereal to use +in the dietary is largely a matter of personal choice. As only a small +amount is usually eaten at a meal, there is little difference in the +quantity of nutrients supplied by the various breakfast cereals. + + + TOTAL AND DIGESTIBLE NUTRIENTS AND FUEL VALUE OF CEREALS + [Transcriber's note: This table has been divided into two + parts to fit limits on page width.] + + ======================================================= + | TOTAL NUTRIENTS | + |-----+----+----+----------+----+ + | | | | C.H. | | + KIND OF FOOD |Water|Pro.|Fat +----+-----+Ash | + | | | |N.F.|Fiber| | + | | | |Ext | | | + ----------------------+-----+----+----+----+-----+----+ + | % | % | % | % | % | % | + Oat Preparations: | | | | | | | + Oats, whole grain | 11.0|11.8| 5.0|59.7| 9.5| 3.0| + Oatmeal, raw | 7.3|16.1| 7.2|66.6| 9.9| 1.9| + Rolled, steam-cooked| 8.2|16.1| 7.4|65.2| 1.3| 1.8| + Wheat: | | | | | | | + Whole grain | 10.5|11.9| 2.1|71.9| 1.8| 1.8| + Cracked wheat | 10.1|11.1| 1.7|73.8| 1.7| 1.6| + Rolled, steam-cooked| 10.6|10.2| 1.8|74.4| 1.8| 1.5| + Shredded wheat | 8.1|10.6| 1.4|76.6| 2.1| 1.8| + Crumbed and malted | 5.6|12.2| 1.0|77.6| 1.7| 1.0| + Farina | 10.9|11.0| 1.4|75.9| 0.4| 0.4| + Rye: | | | | | | | + Whole grain | 11.6|10.6| 1.7|72.5| 1.7| 1.9| + Flaked, to be eaten | 11.1|10.0| 1.4| 75.8 | 1.7| + raw | | | | | | | + Barley: | | | | | | | + Whole grain | 10.9|12.4| 1.8|69.8| 2.7| 2.4| + Pearled barley | 11.5| 8.5| 1.1|77.5| 0.3| 1.1| + Buckwheat: | | | | | | | + Flour | 13.6| 6.4| 1.2|77.5| 0.4| 0.9| + Corn: | | | | | | | + Whole grain | 10.9|10.5| 5.4|69.6| 2.1| 1.5| + Corn meal, unbolted | 11.6| 8.4| 4.7| 74.0 | 1.3| + Corn meal, bolted | 12.5| 9.2| 1.9|74.4| 1.0| 1.0| + Hominy | 10.9| 8.6| 0.6|79.2| 0.4| 0.3| + Pop corn, popped | 4.3|10.7| 5.0|77.3| 1.4| 1.3| + Hulled corn | 74.1| 2.3| 0.9| 22.2 | 0.5| + Rice: | | | | | | | + Whole rice, polished| 12.3| 6.9| 0.3| 80.0 | 0.5| + Puffed rice | 7.1| 6.2| 0.6| 85.7 | 0.4| + Crackers | 6.8|10.7| 8.8|71.4| 0.5| 1.8| + Macaroni | 10.3|13.4| 0.9| 74.1 | 1.3| + ======================================================= + + + ===================================================== + | DIGESTIBLE NUTRIENTS + |----+----+----+----+---------- + | | | | | Fuel + KIND OF FOOD |Pro.|Fat |C.H.|Ash | Value + | | | | | per lb. + | | | | | + ----------------------+----+----+----+----+---------- + | % | % | % | % | Calories. + Oat Preparations: | | | | | + Oats, whole grain | -- | -- | -- | -- | -- + Oatmeal, raw |12.5| 6.5|65.5| 1.4| 1767 + Rolled, steam-cooked|12.5| 6.7|64.5| 1.4| 1759 + Wheat: | | | | | + Whole grain | -- | -- | -- | -- | -- + Cracked wheat | 8.1| 1.5|68.7| 1.2| 1501 + Rolled, steam-cooked| 8.5| 1.6|70.7| 1.1| 1541 + Shredded wheat | 7.7| 1.3|71.1| 1.4| 1521 + Crumbed and malted | 9.1| 0.9|73.7| 1.4| 1623 + Farina | 8.9| 1.3|72.9| 0.5| 1609 + Rye: | | | | | + Whole grain | -- | -- | -- | -- | -- + Flaked, to be eaten | 7.8| 1.3|71.1| 1.3| 1516 + raw | | | | | + Barley: | | | | | + Whole grain | -- | -- | -- | -- | -- + Pearled barley | 6.6| 1.0|73.0| 0.3| 1514 + Buckwheat: | | | | | + Flour | 5.0| 1.1|73.1| 0.7| 1471 + Corn: | | | | | + Whole grain | -- | -- | -- | -- | -- + Corn meal, unbolted | 6.2| 4.2|73.2| 1.0| 1728 + Corn meal, bolted | 6.8| 1.7|74.6| 0.8| 1602 + Hominy | 6.4| 0.5|78.7| 0.2| 1671 + Pop corn, popped | 7.9| 4.5|77.8| 1.0| 1882 + Hulled corn | 1.7| 0.8|21.8| 0.4| 492 + Rice: | | | | | + Whole rice, polished| 5.8| 0.3|78.4| 0.4| 1546 + Puffed rice | 5.1| 0.5|84.0| 0.3| 1639 + Crackers | 9.1| 7.9|70.5| 1.4| 1905 + Macaroni |11.6| 0.8|72.2| 1.0| 1660 + ===================================================== + + + + +CHAPTER X + +WHEAT FLOUR + + +151. Use for Bread Making.--Wheat is particularly adapted to +bread-making purposes because of the physical properties of the gliadin, +one of its proteids. It is the gliadin which, when wet, binds together +the flour particles, enabling the gas generated during bread making to +be retained, and the loaf to expand and become porous. Wheat varies in +chemical composition between wide limits; it may contain as high as 16 +per cent of protein, or as low as 8 per cent; average wheat has from 12 +to 14 per cent; and with these differences in composition, the +bread-making value varies. + +[Illustration: FIG. 36.--STARCHY (LIGHT-COLORED) AND +GLUTINOUS (DARK-COLORED) WHEATS.] + +152. Winter and Spring Wheat Flours.--There are two general classes of +wheat: spring wheat and winter wheat. The winter varieties are seeded in +the fall, and the spring varieties, which are grown mainly in the +Northwestern states, Minnesota, and North and South Dakota, and the +Canadian Northwest, are seeded in the spring and mature in the late +summer. Winter wheat is confined to more southern latitudes and regions +of less severe winter, and matures in the early summer. There are many +varieties of both spring and winter wheat, although wheats are +popularly characterized only as hard or soft, depending upon the +physical properties. The winter wheats are, as a rule, more soft and +starchy than the spring wheats, which are usually corneous or flinty to +different degrees. There is a general tendency for wheats to become +either starchy or glutinous, owing to inherited individuality of the +seed and to environment. There are often found in the same field wheat +plants yielding hard glutinous kernels, and other plants producing +starchy kernels containing 5 per cent less proteids. Wheats of low +protein content do not make high-grade flour; neither do wheats of the +maximum protein content necessarily make the best flour. For a more +extended discussion of wheat proteids, the student is referred to +Chapter XI. + +[Illustration: FIG. 37.--LONGITUDINAL SECTION OF WHEAT KERNEL: +_a_, pericarp; _b_, bran layers; _c_, aleurone cells; _d_, +germ. (After KOeNIG.)] + +153. Composition of Wheat and Flour.--In addition to 12 to 14 per cent +proteids, wheat contains 72 to 76 per cent of starch and small amounts +of other carbohydrates, as sucrose, dextrose, and invert sugar. The ash +or mineral matter ranges from 1.7 to 2.3 per cent. There is also about 2 +per cent fiber, 2.25 per cent ether extract or crude fat, and about 0.2 +per cent organic acids. + +Summary: + +COMPOSITION OF WHEAT FLOUR + + ======================================================== + | Per Cent + Water | 12.00 + | + {Potash } | + {Soda } | + {Lime } | + Ash {Magnesia } | 2.25 + {Phosphoric anhydrid} | + {Sulphuric anhydrid } | + {Other substances } | + | + {Albumin 0.4} | + {Globulin 0.9} | + Protein {Gliadin 6.0} | 13.00 + {Glutenin 5.3} | + {Other proteids 0.4} | + Other nitrogenous bodies, as amids, lecethin | 0.25 + Crude fat, ether extract | 2.25 + Cellulose | 2.25 + Starch | 66.00 + Sucrose, dextrose, soluble carbohydrates, etc.| 2.00 + ======================================================= + +154. Roller Process of Flour Milling.--Flours vary in composition, +food value, and bread-making qualities with the character of the wheat +and the process of milling employed. Prior to 1870 practically all +wheat flour was prepared by grinding the wheat between millstones; but +with the introduction of the roller process, steel rolls were +substituted for millstones.[60] By the former process a smaller amount +of flour was secured from the wheat, but with the present improved +systems about 75 per cent of the weight of the grain is recovered as +merchantable flour and 25 per cent as wheat offals, bran, and +shorts[61]. + +[Illustration: FIG. 38.--GRANULAR WHEAT FLOUR PARTICLES.] + +The wheat is first screened and cleaned, then passed on to the +corrugated rolls, or the first break, where it is partially flattened +and slightly crushed and a small amount of flour, known as the break +flour, is separated by means of sieves, while the main portion is +conveyed through elevators to the second break, where the kernels are +more completely flattened and the granular flour particles are partially +separated from the bran. The material passes over several pairs of rolls +or breaks, each succeeding pair being set a little nearer together. This +is called the gradual reduction process, because the wheat is not made +into flour in one operation. More complete removal of the bran and other +impurities from the middlings is effected by means of sieves, +aspirators, and other devices, and the purified middlings are then +passed on to smooth rolls, where the granulation is completed. The flour +finally passes through silk bolting cloths, containing upwards of 12,000 +meshes per square inch. The dust and fine debris particles are removed +at various points in the process. The granulation of the middlings is +done after the impurities are removed, the object being first to +separate as perfectly as possible the middlings from the branny portions +of the kernel. If the wheat were first ground into a fine meal, it would +be impossible to secure complete separation of the flour from the +offal portions of the kernel. + +[Illustration: FIG. 39.--EXTERIOR OF FLOUR MILL AND WHEAT ELEVATOR.] + +Flour milling is entirely a mechanical process; the flour stock passes +from roll to roll by means of elevators. According to the number of +reductions which the middlings and stock undergo, the milling is +designated as a long or a short reduction system; the term 4, 6, 8, or +10 break process means that the stock has been subjected to that number +of reductions. With an 8-break system of milling, the process is more +gradual than with a 4-break, and greater opportunity is afforded for +complete removal of the bran. In some large flour mills, the wheat is +separated into forty or more different products, or streams, as they are +called, so as to secure a better granulation and more complete removal +of the offals, after which many of these streams are brought together to +form the finished flour. What is known as patent flour is derived from +the reduction of the middlings, while the break flours are recovered +before the offals are completely removed; hence they are not of so high +a grade. No absolute definition can be given, however, of the term +"patent flour," as usage varies the meaning in different parts of the +country. + +155. Grades of Flour.--Flour is the purified, refined, and bolted +product obtained by reduction and granulation of wheat during and after +the removal of the branny portions of the wheat kernel. It is defined by +proclamation of the Secretary of Agriculture, under authority of an +act of Congress, as: "Flour is the fine, sound product made by bolting +wheat meal, and contains not more than thirteen and one half (13.5) per +cent of moisture, not less than one and twenty-five hundredths (1.25) +per cent of nitrogen, not more than one (1) per cent of ash, and not +more than fifty hundredths (0.50) per cent of fiber." + +[Illustration: FIG. 40.--GRINDING FLOOR OF FLOUR MILL, +RUSSELL-MILLER MILLING CO., MINNEAPOLIS, MINN.] + +Generally speaking, flour may be divided into two classes, high grade +and low grade. To the first class belong the first and second patents +and, according to some authorities, a portion of the straight grade, or +standard patent flour, and to the second class belong the second clear +and "red dog." About 72 per cent of the cleaned wheat as milled is +recovered in the higher grades of flour, and about 2 or 3 per cent as +low grades, a large portion of which is sold as animal food. The high +grades are characterized by a lighter color, more elastic gluten, better +granulation, and a smaller number of debris particles. Although the +lower grade flours contain a somewhat higher percentage of protein, they +are not as valuable for bread-making purposes because the gluten is not +as elastic, and consequently they do not make as good bread. If the +impurities from the low grades could be further eliminated, it is +believed that less difference would exist between high and low grade +flours. + +Various trade names are used to designate flours, as a 95 per cent +patent, meaning that 95 per cent of the total flour is included in the +patent; or an 85 per cent patent, when 85 per cent of all the flour is +included in that particular patent. If all the flour streams were +purified and blended, and only one grade of flour made, it would be +called a 100 per cent patent. An 85 per cent patent is a higher grade +flour than a 95 per cent patent. + +[Illustration: FIG. 41.--SILK BOLTING CLOTH USED IN +MANUFACTURE OF FLOUR, MAGNIFIED.] + +156. Composition of Flour.--The composition of the different grades of +flour made from the same wheat is given in the following table:[62] + +COMPOSITION, ACIDITY, AND HEATS OF COMBUSTION OF FLOURS AND OTHER +MILLED PRODUCTS OF WHEAT + + + =========================================================================== + |WATER| PROTEIN | FAT| CARBO-| ASH| ACIDITY | HEAT OF + MILLED PRODUCT | |(N x 5.7)| | HY- | | CALCUL- |COMBUSTION + | | | | DRATES| |ATED AS | PER GRAM + | | | | | |LACTIC |DETERMINED + | | | | | | ACID | + --------------------------------------------------------------------------- + | % | % | % | % | % | % |Calories + First patent flour |10.55| 11.08 |1.15| 76.85 |0.37| 0.08 | 4032 + Second patent flour |10.49| 11.14 |1.20| 76.75 |0.42| 0.08 | 4006 + Straight[A] or | | | | | | | + standard patent |10.54| 11.99 |1.61| 75.36 |0.50| 0.09 | 4050 + flour | | | | | | | + First clear grade |10.13| 13.74 |2.20| 73.13 |0.80| 0.12 | 4097 + flour | | | | | | | + Second clear grade |10.08| 15.03 |3.77| 69.37 |1.75| 0.56 | 4267 + flour | | | | | | | + "Red dog" flour | 9.17| 18.98 |7.00| 61.37 |3.48| 0.59 | 4485 + Shorts | 8.73| 14.87 |6.37| 65.47 |4.56| 0.14 | 4414 + Bran | 9.99| 14.02 |4.39| 65.54 |6.06| 0.23 | 4198 + Entire-wheat flour |10.81| 12.26 |2.24| 73.67 |1.02| 0.32 | 4032 + Graham flour | 8.61| 12.65 |2.44| 74.58 |1.72| 0.18 | 4148 + Wheat | 8.50| 12.65 |2.36| 74.69 |1.80| 0.18 | 4140 + =========================================================================== + +[Footnote A: Straight flour includes the first and second patents and +first clear grade.] + +In the table it will be noted that there is a gradual increase in +protein content from first patent to "red dog," the largest amount being +in the "red dog" flour. Although "red dog" contains the most protein, it +is by far the poorest flour in bread-making qualities, and in the +milling of wheat often it is not separated from the offals, but is sold +as an animal food. It will also be seen that there is a gradual increase +in the ash content from the highest to the lowest grades of flour, the +increase being practically proportional to the grade,--the most ash +being in the lowest grade. The grade to which a flour belongs can be +determined more accurately from the ash content than from any other +constituent. Patent grades of flour rarely contain more than 0.55 per +cent of ash,--the better grades less than 0.5 per cent. The more +completely the bran and offals are removed during the process of +milling, the lower the per cent of ash. The ash content, however, cannot +be taken as an absolute guide in all cases, as noticeable variations +occur in the amount of mineral matter or ash in different wheats; +starchy wheats that have reached full maturity often contain less than +hard wheats grown upon rich soil where the growing season has been +short, and from such wheats a soft, straight flour may have as low a per +cent of ash as a hard first patent flour. When only straight or standard +patent flour is manufactured by a mill, all of the flour is included +which would otherwise be designated first and second patents and first +clear. + +157. Graham and Entire Wheat Flours.--When the germ and a portion of +the bran are retained in the flour, and the particles are not completely +reduced, the product is called "entire wheat flour." The name does not +accurately describe the product, as it includes all of the flour and +only a portion of the bran, and not the entire wheat kernel. Graham +flour is coarsely granulated wheat meal. No sieves or bolting cloths +are employed in its manufacture, and many coarse, unpulverized +particles are present in the product[62]. + +158. Composition of Wheat Offals.--Bran and shorts are characterized +by a high percentage of fiber, or cellulose. The ash, fat, and protein +content of bran are all larger than of flour. The protein, however, is +not in the form of gluten, but is largely albumin and globulins,[16] +which are mainly in the aleurone layer of the wheat kernel, and are +inclosed in branny capsules, and consequently are in a form not readily +digested by man. + +[Illustration: FIG. 42.--FLOUR AND GLUTEN. + +1, flour; 2, dough; 3, moist gluten; 4, dry gluten.] + +The germ is generally included in the shorts, although occasionally it +is removed for special commercial purposes. It is sometimes sterilized +and used in breakfast food products. The germ is rich in oil and is +excluded from the flour mainly because it has a tendency to become +rancid and to impart to the flour poor keeping qualities. Wheat oil has +cathartic properties, and it is believed the physiological action of +whole wheat and graham bread is in part due to the oil. The germ is also +rich in protein, mainly in the form of globulins and proteoses. A dough +cannot be made of pure germ, because it contains so little of the +gliadin and glutenin. + +159. Aging and Curing of Flour.--Flours well milled and made from +high-grade, cleaned wheat generally improve in bread-making value when +stored in clean, ventilated warehouses for periods of three to six +months[9]. High-grade flour becomes drier and whiter and produces bread +of slightly better quality when properly cured by storage. If the flour +is in any way unsound, it deteriorates during storage, due to the action +of ferment bodies. Wheat also, when properly cleaned and stored, +improves in milling and bread-making value. Certain enzymic changes +appear to take place which are beneficial. Wheats differ materially from +year to year in bread-making value, and those produced in seasons when +all the conditions for crop growth are normal do not seem to be so much +improved by storing and aging, either of the wheat or the flour, as when +the growing season has been unfavorable. When wheat is stored, specific +changes occur in both the germ and the cells of the kernel; these +changes are akin to the ripening process, and appear to be greater if, +for any reason, the wheat has failed to fully mature or is abnormal in +composition. + +The flour yield of wheat is in general proportional to the weight per +bushel of the grain, well-filled, heavy grain producing more flour than +light grain.[61] The quality of the flour, however, is not necessarily +proportional to the weight of the grain. It is often necessary to blend +different grades and types of wheat in order to secure good flour. + +160. Macaroni Flour is made from durum wheat, according to Saunders a +variety of hard, spring wheat. It is best grown in regions of restricted +rainfall. Durum and other varieties of hard spring wheat grown under +similar conditions, differ but little in general chemical composition, +except that the gluten of durum appears to have a different percentage +of gliadin and glutenin, and the flour has a more decided yellow color. +Durum wheats are not generally considered as valuable for bread making +as other hard wheat. They differ widely in bread-making value, some +being very poor, while others produce bread of fair quality.[68] + +161. Color.--The highest grades of flour are white in color, or of a +slight creamy tinge. Dark-colored, slaty, and gray flours are of +inferior quality, indicating a poor grade of wheat, poor milling, or a +poor quality of gluten. Flours, after being on the market for a time, +bleach a little and improve to a slight degree in color. Color is one of +the characteristics by which the commercial value of flour is +determined; the whiter the flour, the better the grade, provided other +properties are equal[9]. The color, however, should be a pure or cream +white. Some flours have what is called a dead white color, and, while +not objectionable as far as color is concerned, they are not as valuable +for bread-making and general commercial purposes. One of the principal +trade requirements of a flour is that it possess a certain degree of +whiteness and none of the objectionable shades mentioned. + +To determine the color of a flour, it is compared with a standard. If it +is a winter wheat flour, one of the best high-grade winter patents to be +found on the market is selected, and the sample in question is compared +with this; if it is a spring wheat patent flour, one of the best spring +wheat patent grades is taken as the standard. In making the comparison, +the flours should be placed side by side on a glass plate and smoothed +with the flour trier, the comparison being made preferably by a north +window. Much experience and practice are necessary in order to determine +with accuracy the color value of a flour. + +162. Granulation.--The best patent grades of flour contain an +appreciable amount of granular middlings, which have a characteristic +"feel" similar to fine, sharp sand. A flour which has no granular +feeling is not usually considered of the highest grade, but is generally +a soft wheat flour of poor gluten. However, a flour should not be too +coarsely granulated. The percentage amounts of the different grades of +stock in a flour can be approximately determined by means of sieves and +different sized bolting cloths. To test a flour, ten grams are placed in +a sieve containing a No. 10 bolting cloth; with a camel's-hair brush and +proper manipulation, the flour is sieved, and that which passes through +is weighed. The percentage amount remaining on the No. 10 cloth is +coarser middlings. Nearly all high-grade flours leave no residue on the +No. 10 cloth. The sifted flour from the No. 10 cloth is also passed +through Nos. 11, 12, 13, and 14 cloths[63]. In this way the approximate +granulation of any grade of flour may be determined, and the granulation +of an unknown sample be compared with that of a standard flour. In +determining the granulation of a flour, if there are any coarse or +discolored particles of bran or dust, they should be noted, as it is an +indication of poor milling. When the flour is smoothed with a trier, +there should be no channels formed on the surface of the flour, due to +fibrous impurities caught under the edge of the trier. A hand magnifying +glass is useful for detecting the presence of abnormal amounts of dirt +or fibrous matter in the flour. + +163. Capacity of Flour to absorb Water.--The capacity of a flour to +absorb water is determined by adding water from a burette to a weighed +amount of flour until a dough of standard consistency is obtained. Low +absorption is due to low gluten content. A good flour should absorb from +60 to 65 per cent of its weight of water. In making the test, it is +advisable to determine the absorption of a flour of known baking value +at the same time that an unknown flour is being tested. Flours of low +absorption do not make breads of the best quality; also there are a +smaller number of loaves per barrel, and the bread dries out more +readily. + +164. Physical Properties of Gluten.--The percentages of wet and dry +gluten in a flour are determined as outlined in Experiment No. 27. +Flours of good character should show at least 30 per cent moist gluten +and from 10 to 12 per cent dry gluten. The quality of a flour is not +necessarily proportional to its gluten content, although a flour with +less than 10-1/2 per cent of dry gluten will not make the best quality +of bread, and flours with excessive amounts are sometimes poor bread +makers. The color of the gluten is also important; it should be white or +creamy. The statements made in regard to color of flour apply also to +color of the gluten. A dark, stringy, or putty-like gluten is of little +value for bread-making purposes.[64] In making the gluten test, it is +advisable to compare the gluten with that from a flour of known +bread-making value. Soft wheat flours have a gluten of different +character from hard wheat flours. + +165. Gluten as a Factor in Bread Making.--The bread-making value of a +flour is dependent upon the character of the wheat and the method of +milling. It is not necessarily dependent upon the amount of gluten, as +the largest volume and best quality of bread are often made from flour +of average rather than maximum gluten content. But flours with low +gluten do not produce high-grade breads. When a flour contains more than +12 or 13 per cent of proteids, any increase does not necessarily mean +added bread-making value. The quality of the gluten, equally with the +amount, determines the value for bread-making purposes. + +166. Unsoundness.--A flour with more than 14 per cent of moisture is +liable to become unsound. High acidity also is an indication of +unsoundness or of poor keeping qualities. The odor of a sample of flour +should always be carefully noted, for any suggestion of fermentation +sufficient to affect the odor renders the flour unsuited for making the +best bread. Any abnormal odor in flour is objectionable, as it is due to +contamination of some sort, and most frequently to fermentation changes. +A musty odor is always an indication of unsoundness. Some flours which +have but a slight suggestion of mustiness will, when baked into bread, +have it more pronounced; on the other hand, some odors are removed +during bread making. Flours may absorb odors because of being stored in +contaminated places or being shipped in cars in which oil or other +ill-smelling products with strong odors have previously been shipped. +Unsoundness is often due to faulty methods in handling, as well as to +poor wheat, or to lack of proper cleaning of the wheat or flour. + +[Illustration: FIG. 43.--FUNGOUS GROWTH IN UNSOUND FLOUR.] + +167. Comparative Baking Tests.--To determine the bread-making value of +a flour, comparative baking tests, as outlined in Experiment No. 29, are +made; the flour in question is thus compared as to bread-making value +with a flour of known baking quality. In making the baking tests, the +absorption of the flour, the way in which it responds in the doughing +process, and the general properties of the dough, are noted. The details +should be carried out with care, the comparison always being made with a +similar flour of known baking value, and the bread should be baked at +the same time and under the same conditions as the standard. The color +of the bread, the size and weight of the loaf, and its texture and odor, +are the principal characteristics to be noted. + +[Illustration: FIG. 44.--COMPARATIVE BAKING TESTS.] + +The quality of flour for bread-making purposes is not strictly +dependent upon any one factor, but appears to be the aggregate of a +number of desirable characteristics. The commercial grade of a flour can +be accurately determined from the color, granulation, absorption, gluten +and ash content, and the quality of the bread. Technical flour testing +requires much experience and a high degree of skill. + +168. Bleaching.--In the process of manufacture, flours are often +subjected to air containing traces of nitrogen peroxide gas, generated +by electrical action and resulting in the union of the oxygen and +nitrogen of the air. This whitens and improves the color of the flour. +Bleached flours differ neither in chemical composition nor in nutritive +value from unbleached flours, except that bleached flours contain a +small amount (about one part to one million parts of flour) of nitrite +reacting material, which is removed during the process of bread making. +The amount of nitrites produced in flour during bleaching is less than +is normally present in the saliva, or is found naturally in many +vegetable foods, or in smoked or cured meats, or in bread made from +unbleached flour and baked in a gas oven where nitrites are produced +from combustion of the gas. The bleaching of flour cannot be regarded as +in any way injurious to health or as adulteration, and a bleached flour +which has good gluten and bread-making qualities is entirely +satisfactory. It is not possible to successfully bleach low-grade flours +so they will resemble the high grades, because the bran impurities of +the low grades blacken during bleaching and become more prominent. +Alway, of the Nebraska Experiment Station, has shown that there is no +danger to apprehend from over-bleaching, for when excess of the +bleaching reagent is used, flours become yellow in color[65]. Similar +results have been obtained at the Minnesota Experiment Station. As +bleaching is not injurious to health, and as it is not possible through +bleaching to change low grades so as to resemble the patent grades, +bleaching resolves itself entirely into the question of what color of +flour the consumer desires. Pending the settlement of the status of +bleaching the practice has been largely discontinued. + +[Illustration: FIG. 45.--WHEAT HAIRS AND DEBRIS IN LOW GRADE FLOURS.] + +169. Adulteration of Flour.--Flour is not easily adulterated, as the +addition of any foreign material interferes with the expansion and +bread-making qualities and hence is readily detected. The mixing of +other cereals, as corn flour, with wheat flour has been attempted at +various times when wheat commanded a high price, but this also is +readily detected, by microscopic examination, as the corn starch and +wheat starch grains are quite different in mechanical structure. Such +flours are required to be labeled, in accord with the congressional act +of 1898, when Congress passed, in advance of the general pure food bill, +an act regulating the labeling and sale of mixed and adulterated flours. +Various statements have been made in regard to the adulteration of flour +with minerals, as chalk and barytes, but such adulteration does not +appear to be at all general. + +170. Nutritive Value of Flour.--From a nutritive point of view, wheat +flour and wheat bread have a high value.[66] A larger amount of +nutrients can be secured for a given sum of money in the form of flour +than of any other food material except corn meal. According to +statistics, the average per capita consumption of wheat in the United +States is about 4-1/2 bushels, or, approximately, one barrel per year, +and from recent investigations it would appear that the amount of flour +used in the dietary is on the increase. According to the Bureau of +Labor, flour costs the average laborer about one tenth as much as all +other foods combined, although he secures from it a proportionally +larger amount of nutritive material than from any other food. + + + + +CHAPTER XI + +BREAD AND BREAD MAKING + + +171. Leavened and Unleavened Bread.--To make unleavened bread the +flour is moistened and worked into a stiff dough, which is then rolled +thin, cut into various shapes, and baked, forming a brittle biscuit or +cracker. + +The process of making raised or leavened bread consists, in brief, of +mixing the flour and water in proper proportions for a stiff dough, +together with some salt for seasoning, and yeast (or other agent) for +leavening. The moistened gluten of the flour forms a viscid, elastic, +tenacious mass, which is thoroughly kneaded to distribute the yeast. The +dough is then set in a warm place and the yeast begins to grow, or +"work," causing alcoholic fermentation, with the production of carbon +dioxid gas, which expands the dough, or causes it to "rise," thus +rendering it porous. After the yeast has grown sufficiently, the dough +is baked in a hot oven, where further fermentation is stopped because of +destruction of the yeast by the heat, which also causes the gas to +expand the loaf and, in addition, generates steam. The gas and steam +inflate the tenacious dough and finally escape into the oven. At the +same time the gluten of the dough is hardened by the heat, and the mass +remains porous and light, while the outer surface is darkened and formed +into a crust. + +When the flour is of good quality, the dough well prepared, and the +bread properly baked, the loaf has certain definite characteristics. It +should be well raised and have a thin, flinty crust, which is not too +dark in color nor too tough, but which cracks when broken; the crumb, as +the interior of the loaf is called, should be porous, elastic, and of +uniform texture, without large holes, and should have good flavor, odor, +and color. + +Meal or flour from any of the cereals may be used for unleavened bread, +but leavened bread can be made only from those that contain gluten, a +mixture of vegetable proteids which when moistened with water becomes +viscid, and is tenacious enough to confine the gas produced in the +dough. Most cereals, as barley, rice, oats, and corn, some of which are +very frequently made into forms of unleavened bread, are deficient or +wholly lacking in gluten, and hence cannot be used alone for making +leavened bread. For the leavened bread, wheat and rye, which contain an +abundance of gluten, are best fitted, wheat being in this country by far +the more commonly used. + +172. Changes during Bread Making.--In bread making complex physical, +chemical, and biological changes occur. Each chemical compound of the +flour undergoes some change during the process. The most important +changes are as follows[64]: + +1. Production of carbon dioxid gas, alcohol, and soluble carbohydrates +as the result of ferment action. + +2. Partial rupturing of the starch grains and formation of a small +amount of soluble carbohydrates due to the action of heat. + +3. Production of lactic and other organic acids. + +4. Formation of volatile carbon compounds, other than alcohol and carbon +dioxid. + +5. Change in the solubility of the gluten proteins, due to the action of +the organic acids and fermentation. + +6. Changes in the solubility of the proteids due to the action of heat, +as coagulation of the albumin and globulin. + +7. Formation and liberation of a small amount of volatile, nitrogenous +compounds, as ammonia and amids. + +8. Partial oxidation of the fat. + +173. Loss of Dry Matter during Bread Making.--As many of the compounds +formed during bread making are gases resulting from fermentation action, +and as these are volatile at the temperature of baking, appreciable +losses necessarily take place. Experiments show about 2 per cent of loss +of dry matter under ordinary conditions. These losses are not confined +to the carbohydrates alone, but also extend to the proteids and other +compounds. When 100 pounds of flour containing 10 per cent of water and +90 per cent of dry matter are made into bread, the bread contains about +88 pounds of dry matter. In exceptional cases, where there has been +prolonged fermentation, the losses exceed 2 per cent[64]. + +[Illustration: FIG. 46.--BREWERS' YEAST.] + +174. Action of Yeast.--Yeast is a monocellular plant requiring sugar +and other food materials for its nourishment. Under favorable conditions +it rapidly increases by budding, and as a result produces the well-known +alcoholic fermentation. It requires mineral food, as do plants of a +higher order, and oftentimes the fermentation process is checked for +want of sufficient soluble mineral food. The yeast plant causes a +number of chemical changes to take place, as conversion of starch to a +soluble form and alcoholic fermentation. + + C_{6}H_{10}O_{5} + H_{2}O = C_{6}H_{12}O_{6}. + + C_{6}H_{12}O_{6} = 2 C_{2}H_{5}OH + 2 CO_{2}. + +Alcoholic fermentation cannot occur until the starch has been converted +into dextrose sugar. The yeast plant is destroyed at a temperature of +131 deg. F. It is most active from 70 deg. to 90 deg. F. At a low +temperature it is less active, and when it freezes the cells are ruptured. +A number of different kinds of fermentation are associated with the growth +of the yeast plant, and there are many varieties of yeast, some of which +are more active than others. For bread making an active yeast is desirable +to prevent the formation of acid bodies. If the work proceeds quickly, +the rising process is completed before the acid fermentation is far +advanced. If fermentation is too prolonged, some of the products of the +yeast plant impart an undesirable taste and odor to the bread, and +hinder the development of the gluten and expansion of the loaf. + +175. Compressed Yeast.--The yeast most commonly used in bread making +is compressed yeast, a product of distilleries. The yeast floating on +the surface of the wort is skimmed off and that remaining is allowed to +settle to the bottom, and is obtained by running the wort into shallow +tanks or settling trays. It is then washed with cold water, and the +impurities are removed either by sieving through silk or wire sieves, +or, during the washing, by fractional precipitation. The yeast is then +pressed, cut into cakes, and wrapped in tinfoil. When fresh, it is of +uniform creamy color, moist, and of a firm, even texture[18]. It should +be kept cold, as it readily decomposes. + +176. Dry Yeast is made by mixing starch or meal with fresh yeast until +a stiff dough is formed. This is then dried, either in the sun or at a +moderate temperature, and cut into cakes. By drying, many of the yeast +cells are rendered temporarily inactive, and so it is a slower acting +leaven than the compressed yeast. A dry yeast will keep indefinitely. + +177. Production of Carbon Dioxid Gas and Alcohol.--Carbon dioxid and +alcohol are produced in the largest amounts of any of the compounds +formed during bread making. When the alcoholic ferments secreted by the +yeast plant act upon the invert sugars and produce alcoholic +fermentation, carbon dioxid is one of the products formed. Ordinarily +about 1 per cent of carbon dioxid gas is generated and lost during bread +making. About equal weights of carbon dioxid and alcohol are produced +during the fermentation. In baking, the alcohol is vaporized and aids +the carbon dioxid in expanding the dough and making the bread porous. If +all of the moisture given off during bread making be collected it will +be found that from a pound loaf of bread there are about 40 cubic +centimeters of liquid; when this is submitted to chemical analysis, +small amounts of alcohol are obtained. Alcoholic fermentation sometimes +fails to take place readily, because there are not sufficient soluble +carbohydrates to undergo inversion, or other food for the yeast plant. +Starch cannot be converted directly into alcohol and carbon dioxid gas; +it must first be changed into dextrose sugars, and these undergo +alcoholic fermentation. Bread gives no appreciable reaction for alcohol +even when fresh.[64] + +[Illustration: FIG. 47.--WHEAT STARCH GRANULES AFTER +FERMENTATION WITH YEAST, AS IN BREAD MAKING.] + +If the gluten is of poor quality, or deficient in either gliadin or +glutenin, the dough mass fails to properly expand because the gas is not +all retained. The amount of gas formed is dependent upon temperature, +rapidity of the ferment action, and quality of the yeast and flour. If +the yeast is inactive, other forms of fermentation than the alcoholic +may take place and, as a result, the dough does not expand. Poor yeast +is a frequent cause of poor bread. + +The temperature reached in bread making is not sufficient to destroy all +the ferment bodies associated with the yeast, as, for example, bread +sometimes becomes soft and stringy, due to fermentation changes after +the bread has been baked and stored. Both bread and flour are subject to +many bacterial diseases, and one of the objects of thorough cleaning of +the wheat and removal of the bran and debris particles during the +process of flour manufacture is to completely eliminate all ferment +bodies mechanically associated with the exterior of the wheat kernel, +which, if retained in the flour, would cause it readily to become +unsound. + +178. Production of Soluble Carbohydrates.--Flour contains naturally a +small amount of soluble carbohydrates, which are readily acted upon by +the alcoholic ferments. The yeast plant secretes soluble ferments, which +act upon the starch, forming soluble carbohydrates, and the heat during +baking brings about similar changes. In fact, soluble carbohydrates are +both consumed and produced by ferment action during the bread-making +process. Flour contains, on an average, 65 per cent of starch, and +during bread making about 10 per cent is changed to soluble forms. +Bread, on a dry matter basis, contains approximately 6 per cent of +soluble carbohydrates, including dextrine, dextrose, and sucrose +sugars.[64] + +The physical changes which the starch grains undergo are also +noticeable. Wheat starch has the structure shown in illustration No. 33. +The starch grains are circular bodies, concave, with slight markings in +the form of concentric rings. When the proteid matter of bread is +extracted with alcohol and the starch grains are examined, it will, be +seen that some of them are partially ruptured, like those in popped +corn, while others have been slightly acted upon or eaten away by the +organized ferments, the surface of the starch grains being pitted, as +shown in the illustration. The joint action of heat and ferments on the +starch grains changes them physically so they may more readily undergo +digestion. The brown coating or crust formed upon the surface of bread +is mainly dextrine, produced by the action of heat on the starch. +Dextrine is a soluble carbohydrate, having the same general composition +as starch, but differing from it in physical properties and ease of +digestion. + +179. Production of Acids in Bread Making.--Wheat bread made with yeast +gives an acid reaction. The acid is produced from the carbohydrates by +ferment action. Flour contains about one tenth of 1 per cent of acid; +the dough contains from 0.3 to 0.5 per cent, while the baked bread +contains from 0.14 to 0.3 per cent, but after two or three days slightly +more acid is developed.[64] During the process of bread making, a small +portion of the acid is volatilized, but the larger part enters into +chemical combination with the gliadin, forming an acid proteid. When the +alcoholic fermentation of bread making becomes less active, acid +fermentations begin, and sour dough results. It is not definitely known +what specific organic acids are developed in bread making. Lactic and +butyric acids are known to be formed, and for purposes of calculation, +the total acidity is expressed in terms of lactic acid. + +The acidity is determined by weighing 20 grams of flour into a flask, +adding 200 cubic centimeters of distilled water, shaking vigorously, and +leaving the flour in contact with the water for an hour; 50 cubic +centimeters of the filtered solution are then titrated with a tenth +normal solution of potassium hydroxid. Phenolphthalein is used as the +indicator. It cannot be said that all of the alkali is used for +neutralizing the acid, as a portion enters into chemical combination +with the proteids. If the method for determining the acid be varied, +constant results are not secured. Unsound or musty flours usually show a +high per cent of acidity. + +[Illustration: FIG. 48.--APPARATUS USED IN STUDY OF LOSSES +IN BREAD MAKING.] + +180. Volatile Compounds produced during Bread Making.--In addition to +carbon dioxid and alcohol, there is lost during bread making a small +amount of carbon in other forms, as volatile acids and hydrocarbon +products equivalent to about one tenth of one per cent of carbon dioxid. +The aroma of freshly baked bread is due to these compounds. Both the +odor and flavor of bread are caused in part by the volatile acids and +hydrocarbons. The amount and kind of volatile products formed can be +somewhat regulated through the fermentation process by the use of +special flours and the addition of materials that produce specific +fermentation changes and desirable aromatic compounds. Some of the +ferment bodies left in flour from the imperfect removal of the dirt +adhering to the exterior of the wheat kernels impart characteristic +flavors to the bread. The so-called nutty flavor of some bread is due to +the action of these ferment bodies and, when intensified, it becomes +objectionable. Fungous growths in unsound flour and bread result in the +liberation of volatile products, which impart a musty odor. Good odor +and flavor are very desirable in both flour and bread. + +181. Behavior of Wheat Proteids in Bread Making.--Gluten is an +ingredient of the flour on which its bread-making properties largely +depend. The important thing, however, is not entirely the quantity of +gluten, but more particularly its character. Two flours containing the +same amounts of carbohydrates and proteid compounds, when converted into +bread by exactly the same process, may produce bread of entirely +different physical characteristics because of differences in the nature +of the gluten of the two samples. Gluten is composed of two bodies +called gliadin and glutenin. The gliadin, a sort of plant gelatin, is +the material which binds the flour particles together to form the dough, +thus giving it tenacity and adhesiveness; and the glutenin is the +material to which the gliadin adheres. If there is an excess of gliadin, +the dough is soft and sticky, while if there is a deficiency, it lacks +expansive power. Many flours containing a large amount of gluten and +total proteid material and possessing a high nutritive value, do not +yield bread of the best quality, because of an imperfect blending of the +gliadin and glutenin. This question is of much importance in the milling +of wheats, especially in the blending of the different types of wheat. +An abnormally large amount of gluten does not yield a correspondingly +large loaf. + +[Illustration: FIG. 49.--BREAD FROM NORMAL FLOUR (1); +GLIADIN EXTRACTED FLOUR (2); AND FROM FLOUR AFTER EXTRACTION OF SUGAR +AND SOLUBLE PROTEIDS (3).] + +Experiments were made at the Minnesota Experiment Station to determine +the relation between the nature of the gluten and the character of the +bread. This was done by comparing bread from normal flour with that +from other flour of the same lot, but having part or all of its gliadin +extracted.[64] Dough made from the latter was not sticky, but felt like +putty, and broke in the same way. The yeast caused the mass to expand a +little when first placed in the oven; then the loaf broke apart at the +top and decreased in size. When baked it was less than half the size of +that from the same weight of normal flour, and decidedly inferior in +other respects. The removal of part of the gliadin produced nearly the +same effect as the extraction of the whole of it, and even when an equal +quantity of normal flour was mixed with that from which part of the +gliadin had been extracted, the bread was only slightly improved. In +flour of the highest bread-making properties the two constituents, +gliadin and glutenin, are present in such proportions as to form a +well-balanced gluten. + +The proteids of wheat flour are mainly in an insoluble form, although +there are small amounts of albumins and globulins; these are coagulated +by the action of heat during the bread-making process, and rendered +insoluble. A portion of the acid that is developed unites with the +gliadin and glutenin, forming acid proteids, which change the physical +properties of the dough. Both gliadin and glutenin take important parts +in bread making. The removal of gliadin from flour causes complete loss +of bread-making properties. Ordinarily from 45 to 65 per cent of the +total nitrogen of the flour is present in alcohol soluble or gliadin +form. Proteids also undergo hydration during mixing, some water being +chemically united with them, changing their physical properties. This +hydration change is necessary for the full development of the physical +properties of the gluten. The water and salt soluble proteids appear to +take no important part in the bread-making process, as their removal in +no way affects the size of the loaf or general character of the bread. +Because of the action of the acids upon the gliadin, bread contains a +larger amount of alcohol soluble nitrogen or gliadin than the flour from +which the bread was made. It is believed that this action changes the +molecular structure of the protein so that it is more readily separated +into its component parts when it undergoes digestion and assimilation. + +182. Production of Volatile Nitrogenous Compounds.--When fermentation +is unnecessarily prolonged, an appreciable amount of nitrogen is +volatilized in the form of ammonia and allied bodies, as amids. During +the process of bread making, the yeast appears to act upon the protein, +as well as upon the carbohydrates, and, as previously stated, losses of +dry matter fall alike upon these two classes of compounds, nitrogenous +and non-nitrogenous. Analyses of the flours and materials used in bread +making, and of the bread, show that ordinarily about 1.5 per cent of the +total nitrogen is liberated in the form of gas during the bread-making +process, and analyses of the gases dispelled in baking show +approximately the same per cent of nitrogen. When bread is dried, as in +a drying oven, a small amount of volatile nitrogen appears to be given +off,--probably as ammonium compounds formed during fermentation. The +nitrogen lost in bread making under ordinary conditions is not +sufficient to affect the nutritive value of the product. The losses of +both nitrogen and carbon are more than offset by the increased +solubility of the proteids and carbohydrates, the preliminary changes +they have undergone making them more digestible and valuable for food +purposes. The nitrogen volatilized in bread making appears to be mainly +that present in the flour in amid forms or liberated as the result of +fermentation processes. The more stable proteids undergo only limited +changes in solubility and are not volatilized. + +183. Oxidation of Fat.--Flour contains about 1.25 per cent of fat +mechanically mixed with a small amount of yellow coloring matter. During +the process of bread making the fat undergoes slight oxidation, +accompanied by changes in both physical and chemical properties. The fat +from bread, when no lard or shortening has been added, is darker in +color, more viscous, less soluble in ether, and has a lower iodine +number, than fat from flour. The change in solubility of the fat is not, +however, such as to affect food value, because the fat is not +volatilized, and is only changed by the addition of a small amount of +oxygen from the air. When wheat fat and other vegetable and animal fats +are exposed to the air, they undergo changes known as aging, similar to +the slight oxidation changes in bread making.[64] + +184. Influence of the Addition of Wheat Starch and Gluten to +Flour.--Ten per cent or more of starch may be added to normal flour +containing a well-balanced gluten, without decreasing the size of the +loaf. When moist gluten was added to flour, thus increasing the total +amount of gluten, the size of the loaf was not increased[67]. + + +INFLUENCE OF ADDITION OF STARCH AND GLUTEN TO FLOUR + + ===================================================================== + | SIZE OF LOAF | WEIGHT + --------------------------------------------------------------------- + Wheat flour, 14 ounces | 22-1/2 x 17-1/2 | 18.75 + Wheat flour, 10% wheat starch | 23-1/2 x 17 | 18.25 + Wheat flour, 12.2% wheat starch | 21-1/2 x 17 | 18.00 + | | + Wheat flour, 210 grams, about 8 ounces | 12-3/4 x 9 | 12.00 + Wheat flour, 10% gluten added, 210 grams | 12-1/2 x 9 | 12.75 + Wheat flour, 20% gluten added | 12 x 8-3/4 | 13.00 + ===================================================================== + +So long as the quality of the gluten is not destroyed, the addition of a +small amount of either starch or gluten to flour does not affect the +size of the loaf, but removal of the gluten affects the moisture content +and physical properties of the bread. The addition of starch to flour +has the same effect upon the bread as the use of low gluten +flour,--lessening the capacity of the flour to absorb water and +producing a dryer bread of poorer quality. + +185. Composition of Bread.--The composition of bread depends primarily +upon that of the flour from which it was made. If milk and butter (or +lard) are used in making the dough, as is commonly the case, their +nutrients are, of course, added to those of the flour; but when only +water and flour are used, the nutrients of the bread are simply those +of the flour. In either case the amount of nutrients in the bread is +smaller than in the same weight of flour, because a considerable part of +the water or milk used in making the dough is present in the bread after +baking; that is, a pound of bread contains less of any of the nutrients +than a pound of the flour from which the bread was made, because the +proportion of water in the bread is greater. The following table shows +how the composition of flour compares with that of bread, the different +kinds of bread all having been made from the flour with which they are +compared: + + +COMPOSITION OF FLOUR, AND BREAD MADE FROM IT IN DIFFERENT WAYS + + + ===================================================================== + MATERIAL | WATER | PROTEIN | FAT| C.H.| ASH + --------------------------------------------------------------------- + | % | % | % | % | % + Flour | 10.11 | 12.47 |0.86|76.09 |0.47 + Bread from flour and water | 36.12 | 9.46 |0.40|53.70 |0.32 + Bread from flour, water, and lard | 37.70 | 9.27 |1.02|51.70 |0.31 + Bread from flour and skim milk | 36.02 | 10.57 |0.48|52.63 |0.30 + ===================================================================== + +Thus it may be seen that the proportion of water is larger and of each +nutrient smaller in bread than in flour, and that the nutrients of the +flour are increased by those in the materials added in making the bread. + +It is apparent that two breads of the same lot of flour may differ, +according to the method used in making, and also that two loaves of +bread made by exactly the same process but from different lots of flour, +even when of the same grade or brand, do not necessarily have the same +composition, because of possible variation in the flours. In bread made +from flour of low gluten content, the per cent of protein is +correspondingly low. + +186. Use of Skim Milk and Lard in Bread Making.--When flours low in +gluten are used, skim milk may be employed advantageously in making the +bread, to increase the protein content. Tests show that such bread +contains about 1 per cent more protein than that made with water. +Ordinarily there is no gain from a nutritive point of view in adding an +excessive amount of lard or other shortening, as it tends to widen the +nutritive ratio. + +187. Influence of Warm and Cold Flours on Bread Making.--When flour is +stored in a cold closet or storeroom, it is not in condition to produce +a good quality of bread until it has been warmed to a temperature of +about 70 deg. F. Cold flour checks the fermentation process, and is +occasionally the cause of poor bread. On the other hand, when flour is +too warm (98 deg. F.) the influence upon fermentation is unfavorable. +Heating of flour does not affect the bread-making value, provided the +flour is not heated above 158 deg. F. and is subsequently cooled to a +temperature of 70 deg. F. Wheat flour contains naturally a number of +ferment substances, some of which are destroyed by the action of heat. +The natural ferments, or enzymes, of flour appear to take a part in +bread making, imparting characteristic odors and flavors to the product. + +[Illustration: FIG. 50.-BREAD FROM (1) GRAHAM, (2) ENTIRE +WHEAT, AND (3) WHITE FLOUR. + +The same amounts of flour were used in making all of the breads.] + +188. Variations in the Process of Bread Making.--Since flours differ +so in chemical composition, and the yeast plant acts upon all the +compounds of flour, it naturally follows that bread making is not a +simple but a complex operation, resulting in a number of intricate +chemical reactions, which it is necessary to control and many of which +are only imperfectly understood. Bread of the best physical quality and +commercial value is made of flour from fully matured, hard wheats, +containing a low per cent of acid, no foreign ferment materials or their +products, and at least 12-1/2 per cent of proteids, of which the larger +portion is in the form of gliadin. It is believed that a better quality +of bread could be produced from many flours by slight changes or +modifications in the process of bread making. It cannot be expected that +the same process will give the best results alike with all types and +kinds of flour. The kind of fermentation process that will produce the +best bread from a given type of flour can be determined only by +experimentation. Poor bread making is due as often to lack of skill on +the part of the bread maker, and to poor yeast, as it is to poor quality +of flour. Frequently the flour is blamed when the poor bread is due to +other factors. Lack of control of the fermentation process, and the +consequent development of acid and other organisms which check the +activity of the alcoholic ferments, is a frequent cause of poor bread. + +189. Digestibility of Bread.--Extensive experiments have been made by +the Office of Experiment Stations of the United States Department of +Agriculture, at the Minnesota and Maine Experiment Stations, to +determine the digestibility and nutritive value of bread. Different +kinds and types of wheat were milled so as to secure from each three +flours: graham, entire wheat, and standard patent. The flours were made +into bread, and the bread fed to workingmen, and its digestibility +determined. The experiments taken as a whole show that bread is an +exceedingly digestible food, nearly 98 per cent of the starch or +carbohydrate nutrients and about 88 per cent of the gluten or proteid +constituents being assimilated by the body. In the case of the graham +and entire wheat flours, although they contained a larger total amount +of protein, the nutrients were not as completely digested and absorbed +by the body as were those of the white flour. The body secured a larger +amount of nutrients from the white than from the other grades of flour, +the digestibility of the three types being as follows: standard patent +flour, protein 88.6 per cent and carbohydrates 97.7 per cent; entire +wheat flour, protein 82 percent and carbohydrates 93.5 per cent; graham +flour, protein 74.9 per cent and carbohydrates 89.2 per cent. The low +digestibility of the protein of the graham and entire wheat flours is +supposed to be due to the coarser granulation; the proteins, being +embedded and surrounded with cellular tissue, escape the action of the +digestive fluids. Microscopic examination of the feces showed that often +entire starch grains were still inclosed in the woody coverings and +consequently had failed to undergo digestion.[62], [64], [67], [86] + +190. Use of Graham and Entire Wheat in the Dietary.--Entire wheat and +graham flours should be included in the dietary of some persons, as they +are often valuable because of their physiological action, the branny +particles stimulating the process of digestion and encouraging +peristaltic action. In the diet of the overfed, they are valuable for +the smaller rather than the larger amount of nutrients they contain. +Also they supply bulk and give the digestive tract needed exercise. For +the laboring man, where it is necessary to obtain the largest amount of +available nutrients, bread from white flour should be supplied; in the +dietary of the sedentary, graham and entire wheat flours can, if found +beneficial, be made to form an essential part. The kind of bread that it +is best to use is largely a matter of personal choice founded upon +experience. + + "When we pass on to consider the relative nutritive values of white + and whole-meal bread, we are on ground that has been the scene of + many a controversy. It is often contended that whole-meal is + preferable to white bread, because it is richer in proteid and + mineral matter, and so makes a better balanced diet. But our + examination of the chemical composition of whole-meal bread has + shown that as regards proteid at least, this is not always true, + and even were it the case, the lesser absorption of whole-meal + bread, which we have seen to occur, would tend to annul the + advantage.... On the whole, we may fairly regard the vexed question + of whole-meal _versus_ white bread as finally settled and settled + in favor of the latter."[28] + + "The higher percentage of nitrogen in bran than in fine flour has + frequently led to the recommendation of the coarser breads as more + nutritious than the finer. We have already seen that the more + branny portions of the grain also contain a much larger percentage + of mineral matter. And, further, it is in the bran that the largest + proportion of fatty matter--the non-nitrogenous substance of higher + respiratory capacity which the wheat contains--is found. It is, + however, we think, very questionable whether upon such data alone + a valid opinion can be formed of the comparative values of bread + made from the finer or courser flours ground from one and the same + grain. Again, it is an indisputable fact that branny particles when + admitted into the flour in the degree of imperfect division in + which our ordinary milling processes leave them very considerably + increase the peristaltic action, and hence the alimentary canal is + cleared much more rapidly of its contents. It is also well known + that the poorer classes almost invariably prefer the whiter bread, + and among some of those who work the hardest and who consequently + soonest appreciate a difference in nutritive quality (navvies, for + example) it is distinctly stated that their preference for the + whiter bread is founded on the fact that the browner passes through + them too rapidly; consequently, before their systems have extracted + from it as much nutritious matter as it ought to yield them.... In + fact, all experience tends to show that the state as well as the + chemical composition of our food must be considered; in other + words, that the digestibility and aptitude for assimilation are not + less important qualities than its ultimate composition. + + "But to suppose that whole-wheat meal as ordinarily prepared is, as + has generally been assumed, weight for weight more nutritious than + ordinary bread flour is an utter fallacy founded on theoretical + text-book dicta, not only entirely unsupported by experience, but + inconsistent with it. In fact, it is just the poorer fed and the + harder working that should have the ordinary flour bread rather + than the whole-meal bread as hitherto prepared, and it is the + overfed and the sedentary that should have such whole-meal bread. + Lastly, if the whole grain were finely ground, it is by no means + certain that the percentage of really nutritive nitrogenous matters + would be higher than in ordinary bread flour, and it is quite a + question whether the excess of earthy phosphates would not then be + injurious."--LAWES AND GILBERT.[68] + + * * * * * + + "According to the chemical analysis of graham, entire wheat, and + standard patent flours milled from the same lot of hard Scotch Fife + spring wheat, the graham flour contained the highest and the + patent flour the lowest percentage of total protein. But according + to the results of digestion experiments with these flours the + proportions of digestible or available protein and available energy + in the patent flour were larger than in either the entire wheat or + the graham flour. The lower digestibility of the protein of the + latter is due to the fact that in both these flours a considerable + portion of this constituent is contained in the coarser particles + (bran), and so resists the action of the digestive juices and + escapes digestion. Thus while there actually may be more protein in + a given amount of graham or entire wheat flour than in the same + weight of patent flour from the same wheat, the body obtains less + of the protein and energy from the coarse flour than it does from + the fine, because, although the including of the bran and germ + increases the percentage of protein, it decreases its + digestibility. By digestibility is meant the difference between the + amounts of the several nutrients consumed and the amount excreted + in the feces. + + "The digestibility of first and second patent flours was not + appreciably different from that of standard patent flour. The + degree of digestibility of all these flours is high, due largely to + their mechanical condition; that is, to the fact that they are + finely ground."--SNYDER.[62] + +For a more extended discussion of the subject, the student is referred +to Bulletins 67, 101, and 126, Office of Experiment Stations, United +States Department of Agriculture. + +191. Mineral Content of White Bread.--Average flour contains from 0.4 +to 0.5 of 1 per cent of ash or mineral matter, the larger portion being +lime and magnesia and phosphate of potassium. It is argued by some that +graham and entire wheat flours should be used liberally because of their +larger mineral content and their greater richness in phosphates. In a +mixed dietary, however, in which bread forms an essential part, there is +always an excess of phosphates, and there is nothing to be gained by +increasing the amount, as it only requires additional work of the +kidneys for its removal. Few experiments have been made to determine the +phosphorus requirements of the human body, but these indicate that it is +unnecessary to increase the phosphate content of a mixed diet. It is +estimated that less than two grams per day of phosphates are required to +meet all of the needs of the body, and in an average mixed ration there +are present from three to five grams and more. A large portion of the +phosphate compounds of white bread is present in organic combinations, +as lecithin and nucleated proteids, which are the most available forms, +and more valuable for purposes of nutrition than the mineral phosphates. +In the case of graham and entire wheat flours, a proportionally smaller +amount of the phosphates are digested and assimilated than from the +finer grades of flour. + +192. Comparative Digestibility of New and Old Bread.--With healthy +persons there is no difference whatever in the completeness of +digestibility of old and new bread; one appears to be as thoroughly +absorbed as the other. In the case of some individuals with impaired +digestion there may be a difference in the ease and comfort with which +the two kinds of bread are digested, but this is due mainly to +individuality and does not apply generally. The change which bread +undergoes when it is kept for several days is largely a loss of moisture +and development of a small amount of acid and other substances from the +continued ferment action. + +193. Different Kinds of Bread.--According to variations in method of +preparation, there are different types and varieties of bread, as the +"flat bread" of Scandinavian countries, unleavened bread, Vienna bread, +salt rising bread, etc. Bread made with baking powder differs in no +essential way from that made with yeast, except in the presence of the +residue from the baking powder, discussed in Chapter XII. Biscuits, +wheat cakes, crackers, and other food materials made principally from +flour, have practically the same food value as bread. It makes but +little difference in what way flour is prepared as food, for in its +various forms it has practically the same digestibility and nutritive +value. + +194. Toast.--When bread is toasted there is no change in the +percentage of total nutrients on a dry matter basis. The change is in +solubility and form, and not in amount of nutrients available. Some of +the starch becomes dextrine, which is more soluble and digestible.[5] +Proteids, on the other hand, are rendered less soluble, which appears to +slightly lower the digestion coefficient. They are somewhat more readily +but not quite so completely digested as those of bread. Digestion +experiments show that toast more readily yields to the diastase and +other ferments than does wheat bread. Toasting brings about ease of +digestion rather than increased completeness of the process. Toast is a +sterile food, while bread often contains various ferments which have not +been destroyed by baking. These undergo incubation during the process of +digestion, particularly in the case of individuals with diseases of the +digestive tract. With normal digestion, however, these ferment bodies do +not develop to any appreciable extent, as the digestive tract disinfects +itself. When the flour is prepared from well cleaned wheat and the +ferment substances which are present mainly in the bran particles have +been removed, a flour of higher sanitary value is secured. + + + + +CHAPTER XII + +BAKING POWDERS + + +195. General Composition.--All baking powders contain at least two +materials; one of these has combined carbon dioxid in its composition, +the other some acid constituent which serves to liberate the gas. The +material from which the gas is obtained is almost invariably sodium +bicarbonate, NaHCO_{3}, commonly known as "soda" or "saleratus." +Ammonium carbonate has been used to some extent, but is very seldom used +at the present time. The acid constituent may be one of several +materials, the most common being cream of tartar, tartaric acid, calcium +phosphate, or alum. These may be used separately or in combination. The +various baking powders are designated according to the acid constituent, +as "cream of tartar," "phosphate," and "alum" powders. All of them +liberate carbon dioxid gas, but the products left in the food differ +widely in nature and amount[69]. + +Baking powder is a chemical preparation which, when brought in contact +with water, liberates carbon dioxid gas. The baking powder is mixed dry +with flour, and when this is moistened the carbon dioxid that is +liberated expands the dough. The action is similar to that of yeast +except that in the case of yeast the gas is given off much more slowly +and no residue is left in the bread. When baking powder is used, there +is a residue left in the food which varies with the material in the +powder. It is the nature and amount of this residue that is important +and makes one baking powder more desirable than another. + +[Illustration: FIG. 51.--INGREDIENTS OF A BAKING POWDER. + +1, baking powder; 2, cream of tartar; 3, baking soda; 4, starch.] + +196. Cream of Tartar Powders.--The acid ingredient of the cream of +tartar powders is tartaric acid, H_{2}C_{4}H_{4}O_{6}. Cream of tartar +is potassium acid tartrate, KHC_{4}H_{4}O_{6}; it contains one atom of +replaceable hydrogen, which imparts the acid properties, and it is +prepared from crude argol, a deposit of grape juice when wine is made. +The residue from this powder is sodium potassium tartrate, +NaKC_{4}H_{4}O_{6}, commonly known as Rochelle salt. This is the active +ingredient of Seidlitz powders and has a purgative effect when taken +into the body. The dose as a purgative is from one half to one ounce. A +loaf of bread as ordinarily made with cream of tartar powder contains +about 160 grains of Rochelle salt, which is 45 grains more than is found +in a Seidlitz powder, but the amount actually eaten at any one time is +small and its physiological effect can probably be disregarded. When a +cream of tartar baking powder is used, the reaction takes place +according to the following equation: + + 188 84 210 44 18 + HKH_{4}C_{4}O_{6} + NaHCO_{3} = KNaC_{4}H_{4}O_{6} + CO_{2} + H_{2}O. + +The crystallized Rochelle salt contains four molecules of water, so +that, even allowing for some starch filler, there is very nearly as much +weight of material (Rochelle salt) left in the food as there was of the +original powder. If free tartaric acid were used instead of potassium +acid tartrate, the reaction would be as follows: + + 150 168 230 88 + H_{2}C_{4}H_{4}O{6} + 2NaHCO_{3} = Na_{2}C_{2}H_{4}O_{6}.2 H_{2}O + 2CO_{2}. + +But the residue, sodium tartrate, is less in proportion. It has +physiological properties very similar to Rochelle salt. Tartaric acid is +seldom used alone, but very often in combination with cream of tartar. +It is more expensive than cream of tartar; but not so much is required, +and it is more rapid in action. + +197. Phosphate Baking Powders.--Here the acid ingredient is phosphoric +acid and the compound usually employed is mono-calcium phosphate, +CaH_{4}(PO-{4})_{2}. This is made by the action of sulphuric acid on +ground bone (Ca_{3}(PO_{4})_{2} + 2 H_{2}SO_{4} = CaH_{4}(PO_{4})_{2} + +2 CaSO_{4}), and it is difficult to free it from the calcium phosphate +formed at the same time; hence such powders contain more or less of this +inert material. The reaction which occurs with a phosphate powder is as +follows: + + 234 168 136 + CaH_{4}(PO_{4})_{2} + 2 NaHCO_{3} = CaHPO_{4} + + 88 36 142 + + 2 CO_{2} + 2 H_{2}O + Na_{2}HPO_{4}. + +Sodium phosphate, according to the United States Dispensatory, is +"mildly purgative in doses of from 1 to 2 ounces." The claim is made by +the makers of phosphate baking powders that the phosphates of sodium and +calcium, products left after the baking, restore the phosphates which +have been lost from the flour in the bran. This baking powder residue +does not restore the phosphates in the same form in which they are +present in grains and it does furnish them in larger amounts--nearly +tenfold. However, the residue from these powders is probably less +objectionable than that from alum powders. The chief drawback to the +phosphate powders is their poor keeping qualities. + +198. Alum Baking Powders.--Sulphuric acid is the acid constituent of +these powders. The alums are double sulphates of aluminium and an +alkali metal, and have the general formula _x_Al(SO_{4})_{2} in which +_x_ may be K, Na, or NH_{4}, producing respectively a potash, soda, or +ammonia alum. Potash alum is most commonly used, soda and ammonia alums +to a less extent. The reaction takes place as follows: + + 475 504 157 + 2 NH_{4}Al(SO_{4})_{2} + 6 NaHCO_{3} = Al_{2}(OH)_{6} + + 426 132 264 + + 3 Na_{2}SO_{4} + (NH_{4})_{2}SO_{4} + 6 CO_{2}. + +If it is a potash or soda alum, simply substitute K or Na for NH_{4} +throughout the equation. The best authorities regard alum baking powders +as the most objectionable. Ammonia alum is without doubt the worst form, +since all of the ammonium compounds have an extremely irritating effect +on animal tissue. Sulphates of sodium and potassium are also +objectionable. Aluminium hydroxide is soluble in the slightly acid +gastric juice and has an astringent action on animal tissue, hindering +digestion in a way similar to the alum itself. Many of the alum powders +contain also mono-calcium phosphate; the reaction is as follows: + + 475 234 336 + 2 NH_{4}Al(SO_{4})_{2} + CaH_{4}(PO_{4})_{2} + 4 NaHCO_{3} + + 245 136 132 + = Al_{2}(PO_{4})_{2} + CaSO_{4} + (NH_{4})_{2}SO_{4} + + 284 176 72 + + 2 Na_{2}SO_{4} + 4 CO_{2} + 4 H_{2}O. + +These are probably less injurious than the straight alum powders, +although the residues are, in general, open to the same objection. + +199. Inspection of Baking Powders.--Many of the states have enacted +laws seeking to regulate the sale of alum baking powders. Some of these +laws simply require the packages to bear a label setting forth the fact +that alum is one of the ingredients; others require the baking powder +packages to bear a label naming all the ingredients of the powder. + +200. Fillers.--All baking powders contain a filler of starch. This is +necessary to keep the materials from acting before the powder is used. +The amount of filler varies from 15 to 50 per cent; the least is found +in the tartrate powders and the most in the phosphate powders. The +amount of gas which a powder gives off regulates its value; it should +give off at least 1/8 of its weight. + +201. Home-made Baking Powders.--Baking powders can be made at home for +about one half what they usually cost and they will give equal +satisfaction. The following will make a long-keeping powder: cream of +tartar, 8 ounces; baking soda, 4 ounces; corn starch, 3 ounces. For a +quick-acting powder use but one ounce of starch. The materials should be +thoroughly dry. Mix the soda and starch first by shaking well in a glass +or tin can. Add the cream of tartar last and shake again. Thorough +mixing is essential to good results. Cream of tartar is often +adulterated, but it can be obtained pure from a reliable druggist. To +insure baking powders remaining perfectly dry, they should always be +kept in glass or tin cans, never in paper. + + + + +CHAPTER XIII + +VINEGAR, SPICES, AND CONDIMENTS + + +202. Vinegar.--Vinegar is a dilute solution of acetic acid produced by +fermentation, and contains, in addition to acetic acid, small amounts of +other materials in solution, as mineral matter and malic acid, according +to the material from which the vinegar was made. Unless otherwise +designated, vinegar in this country is generally considered to be made +from apples. Other substances, however, are used, as vinegar can be +manufactured from a variety of fermentable materials, as molasses, +glucose, malt, wine, and alcoholic beverages in general. The chemical +changes which take place in the production of vinegars are: (1) +inversion of the sugar, (2) conversion of the invert sugars into +alcohol, and (3) change of alcohol into acetic acid. All these chemical +changes are the result of ferment action. The various invert ferments +change the sugar into dextrose and glucose sugars; then the alcoholic +ferment produces alcohol and carbon dioxid from the invert sugars, and +finally the acetic acid ferment completes the work by converting the +alcohol into acetic acid. The chemical changes which take place in these +different steps are: + + sucrose dextrose levulose + (1) C_{12}H_{22}O_{11} + H_{2}O = C_{6}H_{12}O_{6} + C_{6}H_{12}O_{6}; + + dextrose alcohol + (2) C_{6}H_{12}O_{6} = 2 C_{2}H_{5}OH + 2 CO_{2}; + + alcohol acid + (3) C_{2}H_{5}OH + 2 O = HC_{2}H_{3}O_{2} + H_{2}O. + +[Illustration: FIG. 52.--ACETIC ACID FERMENTS. (After KOeNIG.)] + +The acetic acid organism, _Mycoderma aceti_, can work only in the +presence of oxygen. It is one of the aerobic ferments, and is present in +what is known as the "mother" of vinegar and is secreted by it. When +vinegar is made in quantity, the process is hastened by allowing the +alcoholic solution to pass through a narrow tank rilled with shavings +containing some of the ferment material, and at the same time air is +admitted so as to secure a good supply of oxygen. When vinegar is made +by allowing cider or wine to stand in a warm place until the +fermentation process is completed, a long time is required--the length +of time depending upon the supply of air and other conditions affecting +fermentation. + +In some countries malt vinegar is common. This is produced by allowing a +wort made from malt and barley to undergo acetic acid fermentation, +without first distilling the alcohol as is done in the preparation of +spirit vinegar. In various European countries wine vinegar is in general +use and is made by acetification of the juice of grapes. Sometimes +spirit vinegar is made from corn or barley malt. Alcoholic fermentation +takes place, the alcohol is distilled so that a weak solution remains, +which is acetified in the ordinary way. Such a vinegar can be produced +very cheaply and is much inferior in flavor to genuine wine or cider +vinegar. + +Vinegar, when properly made, should remain clear, and should not form a +heavy deposit or produce any large amount of the fungous growth, +commonly called the "mother" of vinegar. In order to prevent the vinegar +from becoming cloudy and forming deposits, it should be strained and +stored in clean jugs and protected from the air. So long as air is +excluded further acetic acid fermentation and production of "mother" of +vinegar cannot take place. When the vinegar is properly made and the +fermentation process has been completed, the acid already produced +prevents all further development of acetic acid ferments. When vinegar +becomes cloudy and produces deposits, it is an indication that the +acetic fermentation has not been completed. + +The national standard for pure apple cider vinegar calls for not less +than 4 grams acetic acid, 1.6 grams of apple solids, and 0.25 grams of +apple ash per 100 cubic centimeters, along with other characteristics, +as acidity, sugar, and phosphoric acid content. Many states have special +laws regarding the sale of vinegar. + +203. Adulteration of Vinegar.--Vinegar is frequently adulterated by +the addition of water, or by coloring spirit vinegar, thus causing it to +resemble cider vinegar. Formerly vinegar was occasionally adulterated by +the use of mineral acids, as hydrochloric or sulphuric, but since acetic +acid can be produced so cheaply, this form of adulteration has almost +entirely disappeared. Colored spirit vinegar contains merely a trace of +solid matter and can be readily distinguished from cider vinegar by +evaporating a small weighed quantity to dryness and determining the +weight of the solids. Occasionally, however, glucose and other materials +are added so as to give some solids to the spirit vinegar, but such a +vinegar contains only a trace of ash[18]. Attempts have also been made +to carry the adulteration still further by adding lime and soda to give +the colored spirit vinegar the necessary amount of ash. Malt, white +wine, glucose, and molasses vinegars when properly manufactured and +unadulterated are not objectionable, but too frequently they are made to +resemble and sell as cider vinegar. This is a fraud which affects the +pocketbook rather than the health. For home use apple cider vinegar is +highly desirable. There is no food material or food adjunct, unless +possibly ground coffee and spices, so extensively adulterated as +vinegar. + +Vinegar has no food value whatever, and is valuable only for giving +flavor and palatability to other foods, and to some extent for the +preservation of foods. It is useful in the household in other ways, as +it furnishes a dilute acid solution of aid in some cooking and baking +operations for liberating gas from soda, and also when a dilute acid +solution is required for various cleaning purposes. + +Vinegar should never be kept in tin pails, or any metallic vessel, +because the acetic acid readily dissolves copper, tin, iron, and the +ordinary metals, producing poisonous solutions. Earthenware jugs, +porcelain dishes, glassware, or wooden casks are all serviceable for +storing vinegar. + +204. Characteristics of Spices.[70]--Spices are aromatic vegetable +substances characterized as a class by containing some essential or +volatile oil which gives taste and individuality to the material. They +are used for the flavoring of food and are composed of mineral matter +and the various nitrogenous and non-nitrogenous compounds found in all +plant bodies. Since only a comparatively small amount of a spice is used +for flavoring purposes, no appreciable nutrients are added to the food. +Some of the spices have characteristic medicinal properties. +Occasionally they are used to such an extent as to mask the natural +flavors of foods, and to conceal poor cooking and preparation or poor +quality. For the microscopic study of spices the student is referred to +Winton, "Microscopy of Vegetable Foods," and Leach, "Food Inspection and +Analysis." + +205. Pepper.--Black and white pepper are the fruit of the pepper plant +(_Piper nigrum_), a climbing perennial shrub which grows in the East and +West Indies, the greatest production being in Sumatra. For the black +pepper, the berry is picked before thoroughly ripe; for the white +pepper, it is allowed to mature. White pepper has the black pericarp or +hull removed. Pepper owes its properties to an alkaloid, piperine, and +to a volatile oil. In the black pepper berries there is present ash to +the extent of about 4.5 per cent, it ought not to be above 6.5 per cent; +ether extract, including piperine and resin, not less than 6.5 per cent; +crude fiber not more than 16 per cent; also some starch and nitrogenous +material. The white pepper contains less ash and cellulose than the +black pepper. Ground pepper is frequently grossly adulterated; common +adulterants being: cracker crumbs, roasted nut shells and fruit stones, +charcoal, corn meal, pepper hulls, mustard hulls, and buckwheat +middlings. The pepper berries wrinkle in drying, and this makes it +difficult to remove the sand which may have adhered to them. An +excessive amount of sand in the ash should be classed as adulteration. +Adulterants in pepper are detected mainly by the use of the microscope. +The United States standard for pepper is: not more than 7 per cent total +ash, 15 per cent fiber, and not less than 25 per cent starch and 6 per +cent non-volatile ether extract.[71] + +206. Cayenne.--Cayenne or red pepper is the fruit pod of a plant, +_capsicum_, of which there are several varieties,--the small-fruited +kind, used to make cayenne or red pepper; and the tabasco sort, forming +the basis of tabasco sauce. It is grown mainly in the tropics, and was +used there as a condiment before the landing of Columbus, who took +specimens back to Europe. Cayenne pepper contains 25 per cent of oil, +about 7 per cent of ash, and a liberal amount of starch. The adulterants +are usually of a starchy nature, as rice or corn meal, and the product +is often colored with some red dye. + +207. Mustard.--Mustard is the seed of the mustard plant, and is most +often found in commerce in the ground form. The black or brown mustard +has a very small seed and the most aroma. White mustard is much larger +and is frequently used unground. For the ground mustard, only the +interior of the seed is used, the husk being removed in the bolting. +Mustard contains a large amount of oil, part of which is usually +expressed before grinding, and this is the form in which spice grinders +buy it. In mustard flour there is: ash from 4 to 6 per cent, volatile +oil from 0.5 to 2 per cent, fixed oil from 15 to 25 per cent, crude +fiber from 2 to 5 per cent, albuminoids from 35 to 45 per cent, and a +little starch. The principal adulterants are wheat, corn, and rice +flour. When these are used, the product is frequently colored with +turmeric, a harmless vegetable coloring material. + +208. Ginger.--Ginger is the rhizome or root of a reed-like plant +(_Zingiber officinale_), native in tropical Asia, chiefly India. It is +cultivated in nearly all tropical countries. When unground it usually +occurs in two forms: dried with the epidermis, or with the epidermis +removed, when it is called scraped ginger. Very frequently a coating of +chalk is given, as a protection against the drug store beetle. Jamaica +ginger is the best and most expensive. Cochin, scraped, African, and +Calcutta ginger range in price in the order given. Ginger contains from +3.6 to 7.5 per cent of ash, from 1.5 to 3 per cent of volatile oil, and +from 3 to 5.5 per cent of fixed oil. There is a large amount of starch. +The chief adulterants are rice, wheat, and potato starch, mustard hulls, +exhausted ginger from ginger-ale and extract factories, sawdust and +ground peanut-shells, and turmeric is frequently used for coloring the +product. The United States standard for ginger is not more than 42 per +cent starch, 8 per cent fiber, and 6 per cent total ash.[71] + +209. Cinnamon and Cassia.--The bark of several species of plants +growing in tropical countries furnishes these spices. True cinnamon is a +native of Ceylon, while the cassias are from Bengal and China. In this +country there is more cassia used than cinnamon--cinnamon being rarely +found except in drug stores. Cassia bark is much thicker than cinnamon +bark. The ground spice contains about 1.5 per cent volatile oil and the +same amount of fixed oil, 4 per cent of ash, and some fiber, nitrogenous +matter, and starch. Cereals, cedar sawdust, ground nutshells, oil meal, +and cracker crumbs are the chief adulterants. + +210. Cloves.--Cloves are the flower buds of an evergreen tree that +grows in the tropics. These are picked by hand and dried in the sun. In +the order of value, Penang, Sumatra, Amboyna, and Zanzibar furnish the +chief varieties. Cloves rarely contain more than 8 per cent ash, or less +than 10 per cent volatile oil and 4 per cent fixed oil, and 16 to 20 per +cent of tannin-yielding bodies. No starch is present. The chief +adulterants of ground cloves are spent cloves, allspice, and ground +nutshells. Clove stems are also sometimes used and may be detected by a +microscopical examination, since they contain many thick-walled cells +and much fibrous tissue. + +211. Allspice.--Allspice, or pimento, is the fruit of an evergreen +tree common in the West Indies. It is a small, dry, globular berry, +two-celled, each cell having a single seed. Allspice contains about 2.5 +per cent volatile oil, 4 per cent fixed oil, and 4.5 per cent ash. +Because of its cheapness, it is not generally adulterated, cereal +starches being the most common adulterants. + +212. Nutmeg.--Nutmeg is the interior kernel of the fruit of a tree +growing in the East Indies. The fruit resembles a small pear. A fleshy +mantle of crimson color, which is mace, envelopes the seed. Nutmeg +contains about 2.2 per cent ash, 2.5 to 5 per cent volatile oil, and 25 +to 35 per cent fixed oil. Mace has practically the same composition. +Extensive adulteration is seldom practiced. The white coating on the +surface of the nutmeg is lime, used to prevent sprouting of the germ. + + + + +CHAPTER XIV + +TEA, COFFEE, CHOCOLATE, AND COCOA + + +[Illustration: FIG. 53.--TEA LEAF. (After +WINTON.)] + +213. Tea is the prepared leaf of an evergreen shrub or small tree +cultivated chiefly in China and Japan. There are two varieties of +plants. The Assamese, which requires a very moist, hot climate, yields +in India and Ceylon about 400 pounds per acre, and may produce as high +as 1000 pounds. From this plant a number of flushes or pickings are +secured in a year. The Chinese plant grows in cooler climates and has a +smaller, tougher, and darker leaf, which is more delicate than that of +the Assamese and is usually made into green tea. The Chinese tea plant +yields only four or five flushes a year. About 40 per cent of the tea +used in this country comes from Japan and 50 per cent from China. The +tea industry of India and Ceylon has developed rapidly in late years, +and is now second only to that of China. Tea has been raised upon a +small scale in the United States. The quality or grade of the tea +depends upon the leaves used and the method of curing. + +214. Composition of Tea.--Black and green teas are produced from the +same species of plant, but owe their difference in color as well as +flavor and odor to methods of preparation. The same plant may yield +several grades of both green and black tea. To produce black tea, the +leaves are bruised to liberate the juices, allowed to ferment a short +time, which develops the color, and then dried.[73] For green tea the +fresh leaves are roasted or steamed, then rolled and dried as quickly as +possible to prevent fermentation. The smaller leaves and the first +picking produce the finest quality of tea. The characteristic flavor and +odor of tea are imparted by a volatile oil, although the odor is +sometimes altered by the tea being brought in contact with orange +flowers, jessamine, or the fragrant olive. There are also present in tea +an alkaloid, theine, which gives the peculiar physiological properties, +and tannin, upon which depends largely the strength of the tea infusion. +The composition of tea is as follows: + + =========================================== + |ORIGINAL| GREEN | BLACK + | TEA | TEA | TEA + ------------------------------------------- + Tannin, per cent | 12.91 | 10.64 | 4.89 + Theine, per cent | 3.30 | 3.20 | 3.30 + Ash, per cent | 4.97 | 4.92 | 4.93 + Fiber, per cent | 10.44 | 10.06 | 10.07 + Protein, per cent | 37.33 | 37.43 | 38.90 + (all insoluble) | | | + =========================================== + +It will be noticed that green tea contains twice as much tannin as black +tea; during the fermentation which the black tea undergoes, some of the +tannin is decomposed. There is a large amount of protein in tea, but it +is of no food value, because of its insolubility. About half of the ash +is soluble. The tannin is readily soluble, and for this reason green tea +especially should be infused for a very short time and never boiled. +Tannin in foods in large amounts may interfere with the normal digestion +of the protein compounds, because it coagulates the albumin and peptones +after they have become soluble, and thus makes additional work for the +digestive organs. + +215. Judging Teas.--Teas are judged according to: (1) the tea as it +appears prepared for market, (2) the infusion, and (3) the out-turn +after infusion. The color should be uniform; if a black tea, it should +be grayish black, not a dead black. The leaves should be uniform in size +or grade. The quality and grade are dependent upon flavor, and, with the +strength of the infusion, are determined by tasting. This work is +rapidly done by the trained tea taster. The out-turn should be of one +color; no bright green leaves should be present; evenness of make is +judged by the out-turn. The flavor of a tea is largely a matter of +personal judgment, but from a physiological point of view black teas are +given the preference. + +216. Adulteration of Tea.--A few years ago tea was quite extensively +adulterated, but the strict regulation of the government regarding +imported tea has greatly lessened adulteration. The most common form +was the use of spent leaves, _i.e._ leaves which had been infused. +Leaves of the willow and other plants which resemble tea were also used, +as well as large quantities of tea stems. Facing or coloring is also an +adulteration, since it is done to give poor or damaged tea a brighter +appearance. "Facing consists in treating leaves damaged in manufacture +or which from age are inferior, with a mixture containing Prussian blue, +turmeric, indigo, or plumbago to impart color or gloss, and with a +fraudulent intent. There is no evidence that the facing agents are +deleterious to health in the small quantities used, but as they are used +for purposes of deception, they should be discouraged."[73] Facing and +the addition of stems are the chief adulterations practiced at present. + +217. Food Value and Physiological Properties of Tea.--Tea infusion +does not contain sufficient nutrients to entitle it to be classed as a +food. It is with some persons a stimulant. The caffein or theine in tea +is an alkaloid that has characteristic physiological properties. In +doses of from three to five grains, according to the United States +Dispensatory, "it produces peculiar wakefulness." Larger doses produce +intense physical restlessness, mental anxiety, and obstinate +sleeplessness. "It has no effect upon the motor nerves, but is believed +to have a visible effect upon the sensatory nerves." (United States +Dispensatory.) Experiments with animals show that it causes elevation +of the arterial pressure. It is used as a cardiac stimulant. The +quantity of theine consumed in a cup of tea is about 4/5 of a grain, or +1/4 of a medicinal dose. + +[Illustration: FIG. 54.--COFFEE BERRIES. + +1, Mocha; 2, Java; 3, Rio.] + +218. Composition of Coffee.--The coffee tree is an evergreen +cultivated in the tropics. It grows to a height of 30 feet, but when +cultivated is kept pruned to from 6 to 10 feet. The fruit, which +resembles a small cherry, with two seeds or coffee grains embedded in +the pulp, is dried and the seeds removed, cleaned, and graded. Coffee +has an entirely different composition from tea; it is characterized by +a high per cent of fat and soluble carbohydrates, and also contains an +essential oil and caffein, an alkaloid identical with theine. Tannic +acid, not as free acid, is combined with caffein as a tannate. + + ====================================== + |RAW COFFEE|ROASTED COFFEE + -------------------------------------- + | Per Cent | Per Cent + Water | 11.23 | 1.15 + Ash | 3.92 | 4.75 + Fat | 12.27 | 14.48 + Sugar, etc. | 0.66 | 8.55 + Protein | 12.07 | 13.98 + Caffein | 1.21 | 1.24 + ====================================== + +The high per cent of sugar and other soluble carbohydrates in roasted +coffee is caused by the action of heat upon the non-nitrogenous +compounds. Coffee cannot be considered a food, because only a +comparatively small amount of the nutrients are soluble and available. +It is a mildly stimulating beverage. With some individuals it appears to +promote the digestive process, while with others its effect is not +beneficial. Coffee is more extensively used in this country than tea, +and is subject to greater adulteration. It is adulterated by facing and +glazing; _i.e._ coloring the berries to resemble different grades and +coating them with caramel and dextrine. Spent coffee grains and coffee +that has been extracted without grinding are also used as adulterants. +Imitation berries made of rye, corn, or wheat paste, molded, colored +with caramel, and baked have been found mixed with genuine coffee +berries. Roasted cereals and chicory are used extensively to adulterate +ground coffee. Chicory is prepared from the root of the chicory plant, +which belongs to the same family as the dandelion. It is claimed by some +that a small amount of chicory improves the flavor of coffee. However, +when chicory is added to coffee, it should be so stated on the label and +the amount used given. The dextrine and sugar used in glazing are +browned or caramelized during roasting and impart a darker color to the +infusion, making it appear better than it really is. The glazing also +makes the coffee retain moisture which would otherwise be driven off +during roasting. Coffee contains such a large per cent of oil that the +berries generally float when thrown on water, while the imitation +berries sink. Chicory also sinks rapidly and colors the water brown, +while the coffee remains floating for some time. + +There are three kinds of coffee in general use: Java, Mocha, and Rio or +Brazil. The Brazil coffee has the largest berry and is usually styled by +dealers as "low" or "low middlings." The Java coffee berries are smaller +and paler in color, the better grades being brown. Mocha usually +commands the highest price in commerce. The seeds are small and dark +yellow before roasting. + +219. Cereal Coffee Substitutes. + + "A few of these preparations contain a little true coffee, but for + the most part they appear to be made of parched grains of barley, + wheat, etc., or of grain mixed with pea hulls, ground corncobs, or + wheat middlings. It is said that barley or wheat parched, with a + little molasses, in an ordinary oven, makes something + indistinguishable in flavor from some of the cereal coffees on the + market. If no coffee is used in the cereal preparations, the claim + that they are not stimulating is probably true. As for the + nutritive value, parching the cereals undoubtedly renders some of + the carbohydrates soluble, and a part of this soluble matter passes + into the decoction, but the nutritive value of the infusion is + hardly worth considering in the dietary."[56] + +220. Cocoa and Chocolate Preparations.--Cocoa and chocolate are +manufactured from the "cocoa bean," the seed of a tree native to +tropical America. The beans are inclosed in a lemon-yellow, fleshy pod. +They are removed from the pulp, allowed to undergo fermentation, and +dried by exposure to the air and light, which hardens them and gives +them a red color. This method produces what is known as the "fermented +cocoa." For the "unfermented cocoa," the beans are dried without +undergoing fermentation. Fermentation removes much of the acidity and +bitterness characteristic to the unfermented bean, and when properly +regulated develops flavor. The original bean contains about 50 per cent +fat, part of which is removed in preparing the cocoa. This fat is sold +as cocoa butter. In the preparation of some brands of cocoa, alkalies, +such as soda and potash, are used to form a combination with the fat to +prevent its separating in oily globules. This treatment improves the +appearance of the cocoa, but experiments show the albumin to be somewhat +less digestible and the soap-like product resulting not as valuable a +food as the fat. Such preparations have a high per cent of ash. There +is no objection from a nutritive point of view to a cocoa in which the +fat separates in oily globules. + +221. Composition of Cocoa.--The cocoa bean, when dried or roasted and +freed from its husk and ground, is sold as cracked cocoa, or cocoa nibs. +From cocoa nibs the various cocoa and chocolate preparations are made. +Cocoas vary in composition according to the extent to which the fat is +removed during the process of manufacture and the nature and extent to +which other ingredients are added. An average cocoa contains about 20 +per cent of proteids, and 30 per cent fat, also starch, sugar, gums, +fiber, and ash, as well as theobromine, a material very similar to +theine and caffein in tea and coffee, but not such an active stimulant. +Cocoa is not easily soluble, but it may be ground so fine that a long +time is required for its sedimentation; or sugar or other soluble +material may be added during the process of manufacture to increase the +specific gravity of the liquid to such an extent that the same object is +attained without such fine grinding. The first method is to be +preferred. Cocoa and its preparations are richer in nutritive substances +than tea and coffee and have this added advantage that both the soluble +and insoluble portions become a part of the beverage. Owing to the small +amount used for a cup of cocoa, independent of the milk it does not add +much in the way of nutrients to the ration. + +222. Chocolate.--Plain chocolate is prepared from cocoa nibs without +"removal of the fat or other constituents except the germ." It differs +in chemical composition from cocoa by containing more fat and less +protein; it has nearly the same chemical composition as the cocoa nibs. +It is officially defined as containing "not more than 3 per cent of ash +insoluble in water, 3-1/2 per cent of crude fiber and 9 per cent of +starch, and less than 45 per cent cocoa fat."[71] + +By the addition of sugar, sweet chocolates are made. They vary widely in +composition according to the flavors and amounts of sugar added during +their preparation. The average composition of cocoa nibs, standard +cocoa, and plain chocolate is as follows: + + ============================================================== + | COCOA | COMPOSITION OF | COMPOSITION OF + | NIBS | STANDARD COCOA | PLAIN CHOCOLATE + |--------------------------------------------- + |Per Cent| Per Cent | Per Cent + Water | 3.00 | -- | 3.09 + Ash | 3.50 | 4.20 | 3.08 + Theobromine | 1.00 | -- | -- + Caffein | 0.50 | -- | -- + Crude Protein | 12.00 | -- | -- + Crude fiber | 2.50 | 5.02 | 2.63 + Fat | 50.00 | 32.52 | 49.81 + Starch and other| | | + non-nitrogenous| | | + matter | 27.50 | -- | -- + ============================================================ + +223. Adulteration of Chocolate and Cocoa.--The various chocolate and +cocoa preparations offer an enticing field for sophistication; they are +not, however, so extensively adulterated as before the enforcement of +national and state pure food laws. The most common adulterants are +starch, cocoa shells, and occasionally iron dioxid and other pigments to +give color, also foreign fats to replace the fat removed and to give the +required plasticity for molding. + +224. Comparative Composition of Beverages.--Tea and coffee as +beverages contain but little in the way of nutrients other than the +cream and sugar used in them. The solid matter in tea and coffee +infusions amounts to less than 1.2 per cent. When cocoa is made with +milk, it is a beverage of high nutritive value due mainly to the milk. + + +COMPOSITION OF BEVERAGES[56] + + ============================================================================= + | | | | | FUEL + KIND OF BEVERAGE | WATER | PROTEIN | FAT | CARBO- | VALUE + | | | | HYDRATES | PER LB. + ------------------------|----------|----------|----------|----------|-------- + | Per Cent | Per Cent | Per Cent | Per Cent |Calories + Commercial cereal coffee| | | | | + (0.5 ounce to | | | | | + 1 pint water) | 98.2 | 0.2 | -- | 1.4 | 30 + Parched corn coffee | | | | | + (1.6 ounces to | | | | | + 1 pint water) | 99.5 | 0.2 | -- | 0.5 | 13 + Oatmeal water (1 ounce | | | | | + to 1 pint water) | 99.7 | 0.3 | -- | 0.3 | 11 + Coffee (1 ounce | | | | | + 1 pint water) | 98.9 | 0.2 | -- | 0.7 | 16 + Tea (0.5 ounce to | | | | | + 1 pint water) | 99.5 | 0.2 | -- | 0.6 | 15 + Cocoa (0.5 ounce to | | | | | + 1 pint milk) | 84.5 | 3.8 | 4.7 | 6.0 | 365 + Cocoa (0.5 ounce to | | | | | + 1 pint water) | 97.1 | 0.6 | 0.9 | 1.1 | 65 + Skimmed milk | 90.5 | 3.4 | 0.3 | 5.1 | 170 + ============================================================================= + + + + +CHAPTER XV + +THE DIGESTIBILITY OF FOODS + + +225. Digestibility, How Determined.--The term "digestibility," as +applied to foods, is used in two ways: (1) meaning the thoroughness of +the process, or the completeness with which the nutrients of the food +are absorbed and used by the body, and (2) meaning the ease or comfort +with which digestion is accomplished. Cheese is popularly termed +indigestible, and rice digestible, when in reality the nutrients of +cheese are more completely although more slowly digested than those of +rice. In this work, unless otherwise stated, digestibility is applied to +the completeness of the digestion process. + +The digestibility of a food is ascertained by means of digestion +experiments, in which all of the food consumed for a certain period, +usually two to four days, is weighed and analyzed, and from the weight +and composition is determined the amount, in pounds or grams, of each +nutrient consumed.[72] In like manner the nutrients in the indigestible +portion, or feces, are determined from the weight and composition of the +feces. The indigestible nutrients in the feces are deducted from the +total nutrients of the food, the difference being the amount digested, +or oxidized in the body. When the food is digested, the various +nutrients undergo complete or partial oxidation, with the formation of +carbon dioxid gas, water, urea (CH_{4}N_{2}O), and other compounds. The +feces consist mainly of the compounds which have escaped digestion. The +various groups of compounds of foods do not all have the same +digestibility; for example, the starch of potatoes is 92 per cent +digestible, while the protein is only 72 per cent. The percentage amount +of a nutrient that is digested is called the digestion coefficient. + +In the following way the digestibility of a two-days ration of bread and +milk was determined: 773.5 grams of bread and 2000 grams of milk were +consumed by the subject. The dried feces weighed 38.2 grams. The foods +and feces when analyzed were found to have the following +composition:[62] + + ===================================================================== + COMPOSITION | BREAD | MILK | FECES[A] + --------------------------------------------------------------------- + Water | 44.13 | 86.52 | -- + Crude protein | 7.75 | 3.15 | 25.88 + Ether extract | 0.90 | 4.63 | 18.23 + Ash | 0.32 | 0.70 | 26.35 + Carbohydrates | 46.90 | 5.00 | 29.54 + Calories per gram | 2.450 | 0.79 | 5.083 + ===================================================================== + +[Footnote A: Results on dry-matter basis.] + + +STATEMENT OF RESULTS OF A DIGESTION EXPERIMENT + + ============================================================================= + FOOD CONSUMED | WEIGHT | PROTEIN | ETHER | CARBO- | | HEAT OF + | OF | N x 6.25 | EXTRACT | HY- | ASH | COMBUS- + | MATERIAL | | | DRATES | | TION + ------------------+----------+----------+---------+--------+-------+--------- + | Grams | Grams | Grams | Grams | Grams | Calories + Bread | 773.5 | 60.0 | 6.9 | 362.8 | 2.5 | 1895 + Milk | 2000.0 | 63.0 | 92.6 | 100.0 | 14.0 | 1585 + | | ------- + ------- + -------+-------+--------- + Total | 38.2 | 123.0 | 99.5 | 462.8 | 16.5 | 3480 + Feces | | 9.9 | 7.0 | 11.3 | 10.1 | 194 + | | ------- + ------- + -------+-------+--------- + Total amount | | 113.1 | 92.5 | 451.5 | 6.4 | 3286 + digested | | | | | | + Per cent digested | | | | | | + or coefficients | | | | | | + of digestibility| | 92.0 | 93.0 | 97.5 | 38.8 | 94.4 + | | | | | | + Available energy | | -- | -- | -- | -- | 90.0 + ============================================================================= + +In this experiment 92 per cent of the crude protein, 93 per cent of the +ether extract, and 97.5 per cent of the carbohydrates of the bread and +milk ration were digested and absorbed by the body. In calculating the +available energy, correction is made for the unoxidized residue, as urea +and allied forms. It is estimated that for each gram of protein in the +ration there was an indigestible residue yielding 1.25 calories. + +226. Available Nutrients.--A food may contain a comparatively large +amount of a compound, and yet, on account of its low digestibility, fail +to supply much of it to the body in an available form. Hence it is that +the value of a food is dependent not alone on its composition, but also +on its digestibility. The digestible or available nutrients of a food +are determined by multiplying the per cent of each nutrient which the +food contains by its digestion coefficient. For example, a sample of +wheat flour contains 12 per cent protein, 88 per cent of which is +digestible, making 10.56 per cent of available or digestible protein (12 +x 0.88-10.56). Graham flour made from similar wheat contains 13 per cent +total protein, and only 75 per cent of the protein is digestible, making +9.75 per cent available (13 x 0.75 = 9.75). Thus one food may contain a +larger total but a smaller available amount of a nutrient than another. + +227. Available Energy.--The available energy of a food or a ration is +expressed in calories. A ration for a laborer at active out-of-door work +should yield about 3200 calories. The calory is the unit of heat, and +represents the heat required to raise the temperature of a kilogram of +water 1 deg. C., or four pounds of water 1 deg. F. The caloric value of +foods is determined by the calorimeter, an apparatus which measures heat +with great accuracy. A pound of starch, or allied carbohydrates, yields +1860 calories, and a pound of fat 4225 (see Section 13). While a gram of +protein completely burned produces 7.8 calories, digested it yields only +about 4.2 calories, because, as explained in the preceding section, not +all of the carbon and oxygen are oxidized.[59] The caloric value or +available energy of a ration can be calculated from the digestible +nutrients by multiplying the pounds of digestible protein and +carbohydrates by 1860, the digestible fat by 4225, and adding the +results. For determination of the available energy of foods under +different experimental conditions, and where great accuracy is desired, +a specially constructed respiration calorimeter has been devised, which +is built upon the same principle as an ordinary calorimeter, except it +is large enough to admit a person, and is provided with appliances for +measuring and analyzing the intake and outlet of air.[74] The heat +produced by the combustion of the food in the body warms the water +surrounding the calorimeter chamber, and this increase in temperature is +determined by thermometers reading to 0.005 of a degree or less. + +[Illustration: FIG. 55.--CALORIMETER.] + +228. Normal Digestion and Health.--While the process of digestion has +been extensively studied, it is not perfectly understood. Between the +initial compounds of foods and their final oxidation products a large +number of intermediate substances are formed, and when digestion fails +to take place in a normal way, toxic or poisonous compounds are produced +and various diseases result. It is probable that more diseases are due +to imperfect or malnutrition than to any other cause. There is a very +close relationship between health and normal digestion of the food. + +The cells in the different parts of the digestive tract secrete fluids +containing substances known as soluble ferments, or enzymes, which act +upon the various compounds of foods, changing them chemically and +physically so that they can be absorbed and utilized by the body. (See +Section 31.) Some of the more important ferments are: ptyolin of the +saliva, pepsin of the stomach, and pancreatin and diastase of the +intestines. In order that these ferments may carry on their work in a +normal way, the acidity and alkalinity of the different parts of the +digestive tract must be maintained. The gastric juice contains from 0.1 +to 0.25 per cent of hydrochloric acid, imparting mildly antiseptic +properties; and while the peptic ferment works in a slightly acid +solution, the tryptic ferment requires an alkaline solution. To secrete +the necessary amount and quality of digestive fluids, the organs must be +in a healthy condition. Many erroneous ideas regarding the digestion of +foods are based upon misinterpretation of facts by persons suffering +from impaired digestion, and attempts are frequently made to apply to +normal digestion generalizations applicable only to diseased conditions. + +229. Digestibility of Animal Foods.--The proteids and fats in animal +foods, as meats, are more completely digested than the same class of +nutrients in vegetables. In general, about 95 per cent of the proteids +of meats is digestible, while those in vegetables are often less than 85 +percent digestible. The amount of indigestible residue from animal foods +is small; while from vegetables it is large, for the cellulose prevents +complete absorption of the nutrients and, as a result, there is much +indigestible residue. Animal foods are concentrated, in that they +furnish large amounts of nutrients in digestible forms. There is less +difference in the completeness with which various meats are digested +than in their ease of digestion; the proteins all have about the same +digestion coefficients, but vary with individuals as to ease of +digestion and time required. It is generally considered that the +digestible proteins, whether of animal or vegetable origin, are equally +valuable for food purposes. This is an assumption, however, that has not +been well established by experimental evidence. In a mixed ration, the +proteins from different sources appear to have the same nutritive value, +but as each is composed of different radicals and separated into +dissimilar elementary compounds during the process of digestion, they +would not necessarily all have the same food value. + +There is but little difference between the fats and proteins of meats as +to completeness of digestion,--the slight difference being in favor of +the proteins. Some physiologists claim that the fat, which in some meats +surrounds the bundles of fiber (protein), forming a protecting coat, +prevents the complete solvent action of the digestive fluid. Very fat +meats are not as completely digested as those moderately fat. It is also +claimed that the digestibility of the meat is influenced by the +mechanical character, as toughness of the fiber. + +230. Digestibility of Vegetable Foods.--Vegetable foods vary in +digestibility with their mechanical condition and the amount of +cellulose or fiber. In some the nutrients are so embedded in cellular +tissue as to be protected from the solvent action of the digestive +fluids, and in such cases the digestibility and availability are low. +The starches and sugars are more completely digested than any other of +the nutrients of vegetables; in some instances they are from 95 to 98 +per cent digestible. Some cellular tissue, but not an excess, is +desirable in a ration, as it exerts a favorable mechanical action upon +the organs of digestion, encourages peristalsis, and is an absorbent and +dilutant of the waste products formed during digestion. For example, in +the feeding of swine, it has been found that corn and cob meal often +gives better results than corn fed alone. The cob contains but little in +the way of nutrients, but it exerts a favorable mechanical action upon +digestion. Occasionally too many bulky foods are combined, containing +scant amounts of nutrients, so that the body receives insufficient +protein. This is liable to be the case in the dietary of the strict +vegetarian. Many of the vegetables possess special dietetic value, due +to the organic acids and essential oils, as cited in the chapter on +fruits and vegetables. The value of such foods cannot always be +determined from their content of digestible protein, fat, and +carbohydrates. This is particularly evident when they are omitted from +the ration, as in the case of a restricted diet consisting mainly of +animal foods. Many vegetables have low nutritive value on account of +their bulky nature and the large amount of water and cellulose which +they contain, which tends to decrease digestibility and lower the amount +of available nutrients. Because of their bulk and fermentable nature, +resulting in the formation of gases, a diet of coarse vegetables has a +tendency to cause distention and enlargement of the intestinal organs. +The carbohydrates, which are the chief constituents of vegetables, are +digested mainly in the intestines, and require special mechanical +preparation in the stomach, hence the nutrients of vegetables are not, +as a rule, as easily digested as those of animal foods. + +231. Factors influencing Digestion.--There are a number of factors +which influence completeness as well as ease of digestion, as: (1) +combination of foods; (2) amount of food; (3) method of preparation; (4) +mechanical condition of the food; (5) palatability; (6) physiological +properties; (7) individuality of the consumer; and (8) psychological +influences. + +232. Combination of Foods.--In a mixed ration the nutrients are +generally more completely digested than when only one food is used. For +example, milk is practically all digested when it forms a part of a +ration, and it also promotes digestibility of the foods with which it is +combined, but when used alone it is less digestible.[27] Bread alone and +milk alone are not as completely digested as bread and milk combined. +The same in a general way has been observed in the feeding of farm +animals,--better results are secured from combining two or more foods +than from the use of one alone. The extent to which one food influences +the digestibility of another has not been extensively studied. + +In a mixed ration, consisting of several articles of food of different +mechanical structure, the work of digestion is more evenly distributed +among the various organs. A food often requires special preparation on +the part of the stomach before it can be digested in the intestines, and +if this food is consumed in small amounts and combined with others of +different structure, the work of gastric digestion is lessened so that +the foods are properly prepared and normal digestion takes place. The +effect which one food exerts upon the digestibility of another is +largely mechanical. + +233. Amount of Food.--Completeness as well as ease of digestion is +influenced by the amount of food consumed. In general, excessive amounts +are not as completely digested as moderate amounts. In digestion +experiments with oatmeal and milk, it was found that when these foods +were consumed in large quantities the fat and protein were not as +completely absorbed by the body as when less was used, the protein being +7 per cent and the fat 6 per cent more digestible in the medium ration. +Experiments with animals show that economical results are not secured +from an excess of food.[5] Some individuals consume too much food, and +with them a restricted diet would be beneficial, while others err in not +consuming enough to meet the requirements of the body. Quite frequently +it is those who need more food who practice dieting. When there is +trouble with digestion, it is not always the amount or kind of food +which is at fault, but other habits may be such as to affect digestion. +The active out-of-door laborer can with impunity consume more food, +because there is greater demand for nutrients, and the food is more +completely oxidized in the body and without the formation of poisonous +waste products. The amount of food consumed should be sufficient to meet +all the demands of the body and maintain a normal weight. + +234. Method of Preparation of Food.--The extent to which methods of +cooking and preparation influence completeness of digestion has not been +extensively investigated. As is well known, they have great influence +upon ease and comfort of digestion. During cooking, as discussed in +Chapter II, extensive physical and chemical changes occur, and these in +turn affect digestibility. When the cooking has not been sufficient to +mechanically disintegrate vegetable tissue, the digestive fluids fail to +act favorably upon the food. Cooking is also beneficial because it +renders the food sterile and destroys all objectionable microoerganisms +which, if they remain in food, readily undergo incubation in the +digestive tract, interfering with normal digestion. Prolonged heat +causes some foods to become less digestible, as milk, which digestion +experiments show to be more completely digested when fresh than when +sterilized. Pasteurized milk, which is not subjected to so high a +temperature as sterilized milk, is more completely digested. See Chapter +VII for discussion of sterilizing and pasteurizing milk.[38] The +benefits derived from the destruction of the objectionable bacteria in +foods are, however, greater than the losses attendant on lessened +digestibility due to the action of heat. The method of preparation of a +food affects its digestibility mainly through change in mechanical +structure, and modification of the forms in which the nutrients are +present.[5] + +235. Mechanical Condition of Foods.--The mechanical condition of foods +as to density and structure of the particles and the extent to which +they are disintegrated in their preparation for the table influences +digestibility to a great extent. The mechanics of digestion is a subject +that has not been extensively investigated, and it is one of great +importance, as biological and chemical changes cannot take place if the +food is not in proper mechanical condition. In general, the finer the +food particles, the more completely the nutrients are acted upon by the +digestive fluids and absorbed by the body. Nevertheless, the diet should +not consist entirely of finely granulated foods. Some foods are valuable +mainly because of the favorable action they exert mechanically upon +digestion, rather than for the nutrients they contain.[62] Coarsely +granulated breakfast foods, whole wheat flour, and many vegetables +contain sufficient cellular tissue to give special value from a +mechanical rather than a chemical point of view. The extent to which +coarsely and finely granulated foods should enter into the ration is a +question largely for the individual to determine. Experiments with pigs +show that if large amounts of coarse, granular foods are consumed, the +tendency is for the digestive tract to become inflamed and less able to +exercise its normal functions. Coarsely granulated foods have a tendency +to pass through the digestive tract in less time than those that are +finely granulated, due largely to increased peristaltic action, and the +result is the food is not retained a sufficient length of time to allow +normal absorption to take place. In the feeding of farm animals, it has +been found that the mechanical condition of the food has a great +influence upon its economic use. Rations that are either too bulky or +too concentrated fail to give the best results. In the human ration, the +mechanical condition of the food is equally as important as its chemical +composition. + +236. Mastication is an important part of digestion, and when foods are +not thoroughly masticated, additional work is required of the stomach, +which is usually an overworked organ because of doing the work of the +mouth as well. Although much of the mechanical preparation and mixing of +foods is of necessity done in the stomach, some of it may advantageously +be done in the mouth. The stomach should not be required to perform the +function of the gizzard of a fowl. + +237. Palatability of Foods.--Many foods naturally contain essential +oils and other substances which impart palatability. These have but +little in the way of nutritive value, but they assist in rendering the +nutrients with which they are associated more digestible. Palatability +of a food favorably influences the secretion of the gastric and other +digestive fluids, and in this way the natural flavors of well-prepared +foods aid in digestion. In the feeding of farm animals it has been found +that when foods are consumed with a relish better returns are secured +than when unpalatable foods are fed. To secure palatability the +excessive use of condiments is unnecessary. It is possible to a great +extent during preparation to develop and conserve the natural flavors. +Some foods contain bitter principles which are removed during the +cooking, while in others pleasant flavors are developed. Palatability is +an important factor in the digestibility of foods. + +238. Physiological Properties of Food.--Some food materials, +particularly fruits and vegetables, contain compounds which have +definite physiological properties, as tannin which is an astringent, +special oils which exert a cathartic action, and the alkaloids which +serve as irritants to nerve centers. Wheat germ oil is laxative, and it +is probable that the physiological properties of graham and whole wheat +breads are due in some degree to the oil which they contain.[67] The +use of fruits, herbs, and vegetables for medicinal purposes is based +upon the presence of compounds possessing well-defined medicinal +properties. As a rule food plants do not contain appreciable amounts of +such substances, and the use of food for medicinal effect should be by +the advice of a physician. The physiological properties of some foods +are due to bacterial products. See Chapter XX. + +239. Individuality.--Material difference in digestive power is +noticeable among individuals. Digestion experiments show that one person +may digest 5 per cent more of a nutrient than another. This difference +appears to be due to a number of factors, as activity of the organs, as +affected by exercise and kind of labor performed; abnormal composition +of the digestive fluids; or failure of the different parts of the +digestive tract to act in harmony. Individuality is one of the most +important factors in digestion. Persons become accustomed to certain +foods through long usage, and the digestive tract adapts itself to those +foods, rendering sudden and extreme changes in the dietary hazardous. +Common food articles may fail to properly digest in the case of some +individuals, while with others they are consumed with benefit. What is +food to one may prove to be a poison to another, and while general +statements can be made in regard to the digestibility of foods, +individual differences must be recognized. + +240. Psychological Factors.--Previously conceived ideas concerning +foods influence digestibility. Foods must be consumed with a relish in +order to secure the best results, as flow of the digestive fluids and +activity of the organs are to a certain extent dependent upon the nerve +centers. If it is believed that a food is poisonous or injurious, even +when the food is wholesome, normal digestion fails to take place. In +experiments by the author, in which the comparative digestibility of +butter and oleomargarine was being studied, it was found that when the +subjects were told they were eating oleomargarine, its digestibility was +depressed 5 per cent, and when they were not told the nature of the +material, but assumed that butter was oleomargarine, the digestibility +of the butter was lowered about 6 per cent.[13] Preconceived notions in +regard to foods, not founded upon well-established facts, but due to +prejudice resulting from ignorance, cause many valuable foods to be +excluded from the dietary. Many persons, like the foreign lady who, +visiting this country, said she ate only acquaintances, prefer foods +that have a familiar taste and appearance, and any unusual taste or +appearance detracts from the value because of the psychological +influence upon digestion. + + + + +CHAPTER XVI + +COMPARATIVE COST AND VALUE OF FOODS + + +241. Cost and Nutrient Content of Foods.--The market price and the +nutritive value of foods are often at variance, as those which cost the +most frequently contain the least nutrients.[75] It is difficult to make +absolute comparisons as to the nutritive value of foods at different +prices, because they differ not only in the amounts, but also in the +kinds of nutrients. While it is not possible to express definitely the +value of one food in terms of another, approximate comparisons may be +made as to the amounts of nutrients that can be secured for a given sum +of money when foods are at different prices, and tables have been +prepared making such comparisons. + +[Illustration: FIG. 56.--COMPOSITION OF FOODS. + +(From Office of Experiment Stations Bulletin.)] + +242. Nutrients Procurable for a Given Sum.[7]--To ascertain the +nutrients procurable for a given sum first determine the amount in +pounds that can be obtained, say, for ten cents, and then multiply by +the percentages of fat, protein, carbohydrates, and calories in the +food. The results are the amounts, in pounds, of nutrients procurable +for that sum of money. For example: if milk is 5 cents per quart, two +quarts or approximately four pounds, can be procured for 10 cents. If +the milk contains fat, 4 per cent, protein, 3.3 per cent, carbohydrates, +5 per cent, and fuel value, 310 calories per pound, multiplying each of +these by 4 gives the nutrients and fuel value in four pounds, or 10 +cents worth of milk, as follows: + + Protein 0.13 lb. + Fat 0.16 lb. + Carbohydrates 0.2 lb. + Calories 1240 + +If it is desired to compare milk at 5 cents per quart with round steak +at 15 cents per pound, 10 cents will procure 0.66, or two thirds of a +pound of round steak containing on an average (edible portion) 19 per +cent protein, 12.8 per cent fat, and yielding 890 calories per pound. If +10 per cent is refuse, there is edible about 0.6 of a pound. The amounts +of nutrients in the 0.6 of a pound of steak, edible portion, or 0.66 lb. +as purchased would be: + + Protein 0.11 lb. + Fat 0.08 lb. + Calories 534 + +It is to be observed that from the 10 cents' worth of milk a little more +protein, 0.08 of a pound more fat, and nearly two and one half times as +many calories can be secured as from the 10 cents' worth of meat. This +is due to the carbohydrates and the larger amount of fat which the milk +contains. At these prices, milk should be used liberally in the dietary, +as it furnishes more of all the nutrients than does meat. It would not +be advisable to exclude meat entirely from the ration, but milk at 5 +cents per quart is cheaper food than meat at 15 cents per pound. In +making comparisons, preference cannot always be given to one food +because of its containing more of any particular nutrient, for often +there are other factors that influence the value. + +243. Comparing Foods as to Nutritive Value.--In general, preference +should be given to foods which supply the most protein, provided the +differences between the carbohydrates and fats are not large. When the +protein content of two foods is nearly the same, but the fats and +carbohydrates differ materially, the preference may safely be given to +the food which supplies the larger amount of total nutrients. A pound of +protein in a ration is more valuable than a pound of either fat or +carbohydrates, although it is not possible to establish an absolute +scale as to the comparative value of these nutrients, because they serve +different functional purposes in the body. It is sometimes necessary to +use small amounts of foods rich in protein in order to secure a balanced +ration; excessive use of protein, however, is not economical, as that +which is not needed for functional purposes is converted into heat and +energy which could be supplied as well by the carbohydrates, and they +are less expensive nutrients. + +[Illustration: FIG. 57.--PECUNIARY ECONOMY OF FOOD. + +(From Office of Experiment Stations Bulletin.)] + + +TEN CENTS WILL PURCHASE: (From Farmer's Bulletin No. 142, U. S. +Dept. of Agr.) + + ============================================================================= + | | TOTAL | | | | + | | WEIGHT | | | | + KIND OF FOOD | PRICE | OF FOOD | | | CAR- | + MATERIAL | PER | MATE- |PROTEIN | FAT | BOHY- | ENERGY + | POUND | RIAL | | | DRATES | + ------------------------+-------+---------+--------+-------+---------+------- + | Cents | Pounds | Pound | Pound | Pounds |Calories + Beef, sirloin | 25 | 0.40 | 0.06 | 0.06 | -- | 410 + Do. | 20 | 0.50 | 0.08 | 0.08 | -- | 515 + Do. | 15 | 0.67 | 0.10 | 0.11 | -- | 685 + Beef, round | 16 | 0.63 | 0.11 | 0.08 | -- | 560 + Do. | 14 | 0.71 | 0.13 | 0.09 | -- | 630 + Do. | 12 | 0.83 | 0.15 | 0.10 | -- | 740 + Beef, shoulder clod | 12 | 0.83 | 0.13 | 0.08 | -- | 595 + Do. | 9 | 1.11 | 0.18 | 0.10 | -- | 795 + Beef, stew meat | 5 | 2.00 | 0.29 | 0.23 | -- | 1530 + Beef, dried, chipped | 25 | 0.40 | 0.10 | 0.03 | -- | 315 + Mutton chops, loin | 16 | 0.63 | 0.08 | 0.17 | -- | 890 + Mutton, leg | 20 | 0.50 | 0.07 | 0.07 | -- | 445 + Do. | 16 | 0.63 | 0.09 | 0.09 | -- | 560 + Roast pork, loin | 12 | 0.83 | 0.11 | 0.19 | -- | 1035 + Pork, smoked ham | 22 | 0.45 | 0.06 | 0.14 | -- | 735 + Do. | 18 | 0.56 | 0.08 | 0.18 | -- | 915 + Pork, fat salt | 12 | 0.83 | 0.02 | 0.68 | -- | 2950 + Codfish, dressed, fresh | 10 | 1.00 | 0.11 | -- | -- | 220 + Halibut, fresh | 18 | 0.56 | 0.08 | 0.02 | -- | 265 + Cod, salt | 7 | 1.43 | 0.22 | 0.01 | -- | 465 + Mackerel, salt, dressed | 10 | 1.00 | 0.13 | 0.20 | -- | 1135 + Salmon, canned | 12 | 0.83 | 0.18 | 0.10 | -- | 760 + Oysters, solids, | | | | | | + 50 cents per quart | 25 | 0.40 | 0.02 | -- | 0.01 | 90 + 35 cents per quart | 18 | 0.56 | 0.03 | 0.01 | 0.02 | 125 + Lobster, canned | 18 | 0.56 | 0.10 | 0.01 | -- | 225 + Butter | 20 | 0.50 | 0.01 | 0.40 | -- | 1705 + Do. | 25 | 0.40 | -- | 0.32 | -- | 1365 + Do. | 30 | 0.33 | -- | 0.27 | -- | 1125 + Eggs, 36 cents per dozen| 24 | 0.42 | 0.05 | 0.04 | -- | 260 + Eggs, 24 cents per dozen| 16 | 0.63 | 0.07 | 0.06 | -- | 385 + Eggs, 12 cents per dozen| 8 | 1.25 | 0.14 | 0.11 | -- | 770 + Cheese | 16 | 0.63 | 0.16 | 0.20 | 0.02 | 1185 + Milk, 7 cents per quart | 3-1/2 | 2.85 | 0.09 | 0.11 | 0.14 | 885 + Milk, 6 cents per quart | 3 | 3.33 | 0.11 | 0.13 | 0.17 | 1030 + Wheat flour | 3 | 3.33 | 0.32 | 0.03 | 2.45 | 5440 + Do. | 2-1/2 | 4.00 | 0.39 | 0.04 | 2.94 | 6540 + Corn meal, granular | 2-1/2 | 4.00 | 0.31 | 0.07 | 2.96 | 6540 + Wheat breakfast food | 7-1/2 | 1.33 | 0.13 | 0.02 | 0.98 | 2235 + Oat breakfast food | 7-1/2 | 1.33 | 0.19 | 0.09 | 0.86 | 2395 + Oatmeal | 4 | 2.50 | 0.34 | 0.16 | 1.66 | 4500 + Rice | 8 | 1.25 | 0.08 | -- | 0.97 | 2025 + Wheat bread | 6 | 1.67 | 0.13 | 0.02 | 0.87 | 2000 + Do. | 5 | 2.00 | 0.16 | 0.02 | 1.04 | 2400 + Do. | 4 | 2.50 | 0.20 | 0.03 | 1.30 | 3000 + Rye bread | 5 | 2.00 | 0.15 | 0.01 | 1.04 | 2340 + Beans, white, dried | 5 | 2.00 | 0.35 | 0.03 | 1.16 | 3040 + Cabbage | 2-1/2 | 4.00 | 0.05 | 0.01 | 0.18 | 460 + Celery | 5 | 2.00 | 0.02 | -- | 0.05 | 130 + Corn, canned | 10 | 1.00 | 0.02 | 0.01 | 0.18 | 430 + Potatoes, | | | | | | + 90 cents per bushel | 1-1/2| 6.67 | 0.10 | 0.01 | 0.93 | 1970 + 60 cents per bushel | 1 | 10.00 | 0.15 | 0.01 | 1.40 | 2950 + 45 cents per bushel | 3/4 | 13.33 | 0.20 | 0.01 | 1.87 | 3935 + Turnips | 1 | 10.00 | 0.08 | 0.01 | 0.54 | 1200 + Apples | 1-1/2| 6.67 | 0.02 | 0.02 | 0.65 | 1270 + Bananas | 7 | 1.43 | 0.01 | 0.01 | 0.18 | 370 + Oranges | 6 | 1.67 | 0.01 | -- | 0.13 | 250 + Strawberries | 7 | 1.43 | .01 | 0.01 | 0.09 | 215 + Sugar | 6 | 1.67 | -- | -- | 1.67 | 2920 + ============================================================================= + +It is to be noted in the table that, ordinarily, for the same amount of +money the most nutrients can be obtained in the form of milk, cheese, +sugar, and beans, corn meal, wheat flour, oatmeal, and cereals in bulk. +While meats supply protein liberally, they fail to furnish carbohydrates +as the vegetables. As discussed in the chapter on Dietary Studies of +Families, unnecessarily expensive foods are often used, resulting either +in lack of nutrients or unbalanced rations. + + +EXAMPLES + +1. Compute the calories and the amounts of protein, fat, and +carbohydrates that can be procured for 25 cents in cheese selling for 18 +cents per pound; how do these compare with the nutrients in eggs at 20 +cents per dozen? + +2. Which food furnishes the larger amount of nutrients, potatoes at 50 +cents per bushel or flour at $6 per barrel? + +3. How do beans at 10 cents per quart compare in nutritive value with +beef at 15 Cents per pound? + +4. How does salt codfish at 10 cents per pound compare in nutritive +value with lamb chops at 15 cents per pound? + +5. Compare in nutritive value cream at 25 cents per quart with butter at +30 cents per pound. + +6. Calculate the composition and nutritive value of a cake made of +sugar, 8 oz.; butter, 4 oz.; eggs, 8 oz.; flour, 8 oz.; and milk, 4 oz.; +the baked cake weighs one and three fourths pounds. + + +AVERAGE COMPOSITION OF COMMON AMERICAN FOOD PRODUCTS + +(From Farmer's Bulletin, No. 142, U. S. Dept. of Agr.) + + ============================================================================= + | | | | | | | F + | | | | | h | | u p + | R | | P | | C y | | e e + | e | W | r | | a d | | l r + | f | a | o | F | r r | A | + Food Material | u | t | t | a | b a | s | v P + (as purchased) | s | e | e | t | o t | h | a o + | e | r | i | | - e | | l u + | | | n | | s | | u n + | | | | | | | e d + ------------------------------+------+------+------+------+-----+-----+------ + | | | | | | | Calo- + ANIMAL FOOD | % | % | % | % | % | % | ries + | | | | | | | + Beef, fresh: | | | | | | | + Chuck ribs | 16.3 | 52.6 | 15.5 | 15.0 | -- | 0.8 | 910 + Flank | 10.2 | 54.0 | 17.0 | 19.0 | -- | 0.7 | 1105 + Loin | 13.3 | 52.5 | 16.1 | 17.5 | -- | 0.9 | 1025 + Porterhouse steak | 12.7 | 52.4 | 19.1 | 17.9 | -- | 0.8 | 1100 + Sirloin steak | 12.8 | 54.0 | 16.5 | 16.1 | -- | 0.9 | 975 + Neck | 27.6 | 45.9 | 14.5 | 11.9 | -- | 0.7 | 1165 + Ribs | 20.8 | 43.8 | 13.9 | 21.2 | -- | 0.7 | 1135 + Rib rolls | -- | 63.9 | 19.3 | 16.7 | -- | 0.9 | 1055 + Round | 7.2 | 60.7 | 19.0 | 12.8 | -- | 1.0 | 890 + Rump | 20.7 | 45.0 | 13.8 | 20.2 | -- | 0.7 | 1090 + Shank, fore | 36.9 | 42.9 | 12.8 | 7.3 | -- | 0.6 | 545 + Shoulder and clod | 16.4 | 56.8 | 16.4 | 9.8 | -- | 0.9 | 715 + Fore quarter | 18.7 | 49.1 | 14.5 | 17.5 | -- | 0.7 | 995 + Hind quarter | 15.7 | 50.4 | 15.4 | 18.3 | -- | 0.7 | 1045 + Beef, corned, canned, | | | | | | | + pickled, dried: | | | | | | | + Corned beef | 8.4 | 49.2 | 14.3 | 23.8 | -- | 4.6 | 1245 + Tongue, pickled | 6.0 | 58.9 | 11.9 | 19.2 | -- | 4.3 | 1010 + Dried, salted, and smoked | 4.7 | 53.7 | 26.4 | 6.9 | -- | 8.9 | 790 + Canned boiled beef | -- | 51.8 | 25.5 | 22.5 | -- | 1.3 | 1410 + Canned corned beef | -- | 51.8 | 26.3 | 18.7 | -- | 4.0 | 1270 + Veal: | | | | | | | + Breast | 21.3 | 52.0 | 15.4 | 11.0 | -- | 0.8 | 745 + Leg | 14.2 | 60.1 | 15.5 | 7.9 | -- | 0.9 | 625 + Leg cutlets | 3.4 | 68.3 | 20.1 | 7.5 | -- | 1.0 | 695 + Fore quarter | 24.5 | 54.2 | 15.1 | 6.0 | -- | 0.7 | 535 + Hind quarter | 20.7 | 56.2 | 16.2 | 6.6 | -- | 0.8 | 580 + Mutton: | | | | | | | + Flank | 9.9 | 39.0 | 13.8 | 36.9 | -- | 0.6 | 1770 + Leg, hind | 18.4 | 51.2 | 15.1 | 14.7 | -- | 0.8 | 890 + Loin chops | 16.0 | 42.0 | 13.5 | 28.3 | -- | 0.7 | 1415 + Fore quarter | 21.2 | 41.6 | 12.3 | 24.5 | -- | 0.7 | 1235 + Hind quarter, without | 17.2 | 45.4 | 13.8 | 23.2 | -- | 0.7 | 1210 + tallow | | | | | | | + Lamb: | | | | | | | + Breast | 10.1 | 45.5 | 15.4 | 19.1 | -- | 0.8 | 1075 + Leg, hind | 17.4 | 52.9 | 15.9 | 13.6 | -- | 0.9 | 860 + Pork, fresh: | | | | | | | + Ham | 10.7 | 48.0 | 13.5 | 25.9 | -- | 0.8 | 1320 + Loin chops | 19.7 | 41.8 | 13.4 | 24.2 | -- | 0.8 | 1245 + Shoulder | 12.4 | 44.9 | 12.0 | 29.8 | -- | 0.7 | 1450 + Tenderloin | -- | 66.5 | 18.9 | 13.0 | -- | 1.0 | 895 + Pork, salted, cured, pickled: | | | | | | | + Ham, smoked | 13.6 | 34.8 | 14.2 | 33.4 | -- | 4.2 | 1635 + Shoulder, smoked | 18.2 | 36.8 | 13.0 | 26.6 | -- | 5.5 | 1335 + Salt pork | -- | 7.9 | 1.9 | 86.2 | -- | 3.9 | 3555 + Bacon, smoked | 7.7 | 17.4 | 9.1 | 62.2 | -- | 4.1 | 2715 + Sausage: | | | | | | | + Bologna | 3.3 | 55.2 | 18.2 | 19.7 | -- | 3.8 | 1155 + Pork | -- | 39.8 | 13.0 | 44.2 | 1.1| 2.2 | 2075 + Frankfort | -- | 57.2 | 19.6 | 18.6 | 1.1| 3.4 | 1155 + Soups: | | | | | | | + Celery, cream of | -- | 88.6 | 2.1 | 2.8 | 5.0| 1.5 | 235 + Beef | -- | 92.9 | 4.4 | 0.4 | 1.1| 1.2 | 120 + Meat stew | -- | 84.5 | 4.6 | 4.3 | 5.5| 1.1 | 365 + Tomato | -- | 90.0 | 1.8 | 1.1 | 5.6| 1.5 | 185 + Poultry: | | | | | | | + Chicken, broilers | 41.6 | 43.7 | 12.8 | 1.4 | -- | 0.7 | 305 + Fowls | 25.9 | 47.1 | 13.7 | 12.3 | -- | 0.7 | 765 + Goose | 17.6 | 38.5 | 13.4 | 29.8 | -- | 0.7 | 1475 + Turkey | 22.7 | 42.4 | 16.1 | 18.4 | -- | 0.8 | 1060 + Fish: | | | | | | | + Cod, dressed | 29.9 | 58.5 | 11.1 | 0.2 | -- | 0.8 | 220 + Halibut, steaks or sections | 17.7 | 61.9 | 15.3 | 4.4 | -- | 0.9 | 475 + Mackerel, whole | 44.7 | 40.4 | 10.2 | 4.2 | -- | 0.7 | 370 + Perch, yellow dressed | 35.1 | 50.7 | 12.8 | 0.7 | -- | 0.9 | 275 + Shad, whole | 50.1 | 35.2 | 9.4 | 4.8 | -- | 0.7 | 380 + Shad, roe | -- | 71.2 | 20.9 | 3.8 | 2.6| 1.5 | 600 + Fish, preserved: | | | | | | | + Cod, salt | 24.9 | 40.2 | 16.0 | 0.4 | -- |18.5 | 325 + Herring, smoked | 44.4 | 19.2 | 20.5 | 8.8 | -- | 7.4 | 755 + Fish, canned | | | | | | | + Salmon | -- | 63.5 | 21.8 | 12.1 | -- | 2.6 | 915 + Sardines |[A]5.0| 53.6 | 23.7 | 12.1 | -- | 5.3 | 950 + Shellfish: | | | | | | | + Clams | -- | 80.8 | 10.6 | 1.1 | 5.2 | 2.3| 340 + Crabs | 52.4 | 36.7 | 7.9 | 0.9 | 0.6 | 1.5| 200 + Lobsters | 61.7 | 30.7 | 5.9 | 0.7 | 0.2 | 0.8| 145 + Eggs: Hen's eggs [B]|11.2 | 65.5 | 13.1 | 9.3 | -- | 0.9| 635 + Dairy products, etc.: | | | | | | | + Butter | -- | 11.0 | 1.0 |85.0 | -- | 3.0| 3410 + Whole milk | -- | 87.0 | 3.3 | 4.0 | 5.0 | 0.7| 310 + Skim milk | -- | 90.5 | 3.4 | 0.3 | 5.1 | 0.7| 165 + Buttermilk | -- | 91.0 | 3.0 | 0.5 | 4.8 | 0.7| 160 + Condensed milk | -- | 26.9 | 8.8 | 8.3 |54.1 | 1.9| 1430 + Cream | -- | 74.0 | 2.5 |18.5 | 4.5 | 0.5| 865 + Cheese, Cheddar | -- | 27.4 | 27.7 |36.8 | 4.1 | 4.0| 2075 + Cheese, full cream | -- | 34.2 | 25.9 |33.7 | 2.4 | 3.8| 1885 + | | | | | | | + VEGETABLE FOOD | | | | | | | + | | | | | | | + Flour, meal, etc.: | | | | | | | + Entire wheat flour | -- | 11.4 | 13.8 | 1.9 |71.9 | 1.0| 1650 + Graham flour | -- | 11.3 | 13.3 | 2.2 |71.4 | 1.8| 1645 + Wheat flour, patent | | | | | | | + roller process | | | | | | | + High-grade and medium | -- | 12.0 | 11.4 | 1.0 |75.1 | 0.5| 1635 + Low grade | -- | 12.0 | 14.0 | 1.9 |71.2 | 0.9| 1640 + Macaroni, vermicelli, etc | -- | 10.3 | 13.4 | 0.9 |74.1 | 1.3| 1645 + Wheat breakfast food | -- | 9.6 | 12.1 | 1.8 |75.2 | 1.3| 1680 + Buckwheat flour | -- | 13.6 | 6.4 | 1.2 |77.9 | 0.9| 1605 + Rye flour | -- | 12.9 | 6.8 | 0.9 |78.7 | 0.7| 1620 + Corn meal | -- | 12.5 | 9.2 | 1.9 |75.4 | 1.0| 1635 + Oat breakfast food | -- | 7.7 | 16.7 | 7.3 |66.2 | 2.1| 1800 + Rice | -- | 12.3 | 8.0 | 0.3 |79.0 | 0.4| 1620 + Tapioca | -- | 11.4 | 0.4 | 0.1 |88.0 | 0.1| 1650 + Starch | -- | -- | -- | -- |90.0 | -- | 1675 + Bread, pastry, etc.: | | | | | | | + White bread | -- | 35.3 | 9.2 | 1.3 |53.1 | 1.1| 1200 + Brown bread | -- | 43.6 | 5.4 | 1.8 |47.1 | 2.1| 1040 + Bread, pastry, etc.: | | | | | | | + Graham bread | -- | 35.7 | 8.9 | 1.8| 52.1| 1.5 | 1195 + Whole wheat bread | -- | 38.4 | 9.7.| 0.9| 49.7| 1.3 | 1130 + Rye bread | -- | 35.7 | 9.0.| 0.6| 53.2| 1.5 | 1170 + Cake | -- | 19.9 | 6.3.| 9.0| 63.3| 1.5 | 1630 + Cream crackers | -- | 6.8 | 9.7.| 12.1| 69.7| 1.7 | 1925 + Oyster crackers | -- | 4.8 | 11.3.| 10.5| 70.5| 2.9 | 1910 + Soda crackers | -- | 5.9 | 9.8.| 9.1| 73.1| 2.1 | 1875 + | | | | | | | + Sugars, etc.: | | | | | | | + | | | | | | | + Molasses | -- | -- | -- | -- | 70.0| -- | 1225 + Candy[C] | -- | -- | -- | -- | 96.0| -- | 1680 + Honey | -- | -- | -- | -- | 81.0| -- | 1420 + Sugar, granulated | -- | -- | -- | -- |100.0| -- | 1750 + Maple sirup | -- | -- | -- | -- | 71.4| -- | 1250 + | | | | | | | + Vegetables:[D] | | | | | | | + Beans, dried | -- | 12.6 | 22.5.| 1.8| 59.6| 3.5 | 1520 + Beans, Lima, shelled | -- | 68.5 | 7.1.| 0.7| 22.0| 1.7 | 540 + Beans, string | 7.0 | 83.0 | 2.1.| 0.3| 6.9| 0.7 | 170 + Beets | 20.0 | 70.0 | 1.3.| 0.1| 7.7| 0.9 | 160 + Cabbage | 15.0 | 77.7 | 1.4.| 0.2| 4.8| 0.9 | 115 + Celery | 20.0 | 75.6 | 0.9.| 0.1| 2.6| 0.8 | 65 + Corn, green (sweet), | | | | | | | + edible portion | -- | 75.4 | 3.1 | 1.1| 19.7| 0.7 | 440 + Cucumbers | 15.0 | 81.1 | 0.7.| 0.2| 2.6| 0.4 | 65 + Lettuce | 15.0 | 80.5 | 1.0.| 0.2| 2.5| 0.8 | 65 + Mushrooms | -- | 88.1 | 3.5 | 0.4| 6.8| 1.2 | 185 + Onions | 10.0 | 78.9 | 1.4.| 0.3| 8.9| 0.5 | 190 + Parsnips | 20.0 | 66.4 | 1.3.| 0.4| 10.8| 1.1 | 230 + Peas _(Pisum sativum),_ | | | | | | | + dried. | -- | 9.5 | 24.6 | 1.0| 62.0| 2.9 | 1565 + shelled | -- | 74.6 | 7.0 | 0.5| 16.9| 1.0 | 440 + Cowpeas, dried | -- | 13.0 | 21.4.| 1.4| 60.8| 3.4 | 1505 + Potatoes | 20.0 | 62.6 | 1.8.| 0.1| 14.7| 0.8 | 295 + Vegetables: | | | | | | | + Rhubarb | 40.0 | 56.6 | 0.4 | 0.4 | 2.2| 0.4 | 60 + Sweet potatoes | 20.0 | 55.2 | 1.4 | 0.6 | 21.9| 0.9 | 440 + Spinach | -- | 92.3 | 2.1 | 0.3 | 3.2| 2.1 | 95 + Squash | 50.0 | 44.2 | 0.7 | 0.2 | 4.5| 0.4 | 100 + Tomatoes | -- | 94.3 | 0.9 | 0.4 | 3.9| 0.5 | 100 + Turnips | 30.0 | 62.7 | 0.9 | 0.1 | 5.7| 0.6 | 120 + Vegetables, canned: | | | | | | | + Baked beans | -- | 68.9 | 6.9 | 2.5 | 19.6| 2.1 | 555 + Peas _(Pisum sativum),_ | | | | | | | + green | -- | 85.3 | 3.6 | 0.2 | 9.8| 1.1 | 235 + Corn, green | -- | 76.1 | 2.8 | 1.2 | 19.0| 0.9 | 430 + Succotash | -- | 75.9 | 3.6 | 1.0 | 18.6| 0.9 | 425 + Tomatoes | -- | 94.0 | 1.2 | 0.2 | 4.0| 0.6 | 95 + Fruits, berries, etc., | | | | | | | + fresh: [E] | | | | | | | + Apples | 25.0 | 63.3 | 0.3 | 0.3 | 10.8| 0.3 | 190 + Bananas | 35.0 | 48.9 | 0.8 | 0.4 | 14.3| 0.6 | 260 + Grapes | 25.0 | 58.0 | 1.0 | 1.2 | 14.4| 0.4 | 295 + Lemons | 30.0 | 62.5 | 0.7 | 0.5 | 5.9| 0.4 | 125 + Muskmelons | 50.0 | 44.8 | 0.3 | -- | 4.6| 0.3 | 80 + Oranges | 27.0 | 63.4 | 0.6 | 0.1 | 8.5| 0.4 | 150 + Pears | 10.0 | 76.0 | 0.5 | 0.4 | 12.7| 0.4 | 230 + Persimmons, edible portion | -- | 66.1 | 0.8 | 0.7 | 31.5| 0.9 | 550 + Raspberries | -- | 85.8 | 1.0 | -- | 12.6| 0.6 | 220 + Strawberries | 5.0 | 85.9 | 0.9 | 0.6 | 7.0| 0.6 | 150 + Watermelons | 59.4 | 37.5 | 0.2 | 0.1 | 2.7| 0.1 | 50 + Fruits, dried: | | | | | | | + Apples | -- | 28.1 | 1.6 | 2.2 | 66.1| 2.0 | 1185 + Apricots | -- | 29.4 | 4.7 | 1.0 | 62.5| 2.4 | 1125 + Dates | 10.0 | 13.8 | 1.9 | 2.5 | 70.6| 1.2 | 1275 + Fruits, dried: | | | | | | | + Rhubarb | 40.0 | 56.6 | 0.4 | 0.4 | 2.2| 0.4 | 60 + | | | | | | | + Figs | -- | 18.8 | 4.3 | 0.3 | 74.2| 2.4 | 1280 + Raisins | 10.0 | 13.1 | 2.3 | 3.0 | 68.5| 3.1 | 1265 + Nuts: | | | | | | | + Almonds | 45.0 | 2.7 | 11.5 | 30.2 | 9.5| 1.1 | 1515 + Brazil nuts | 49.6 | 2.6 | 8.6 | 33.7 | 3.5| 2.0 | 1485 + Butternuts | 86.4 | 0.6 | 3.8 | 8.3 | 0.5| 0.4 | 385 + Chestnuts, fresh | 16.0 | 37.8 | 5.2 | 4.5 | 35.4| 1.1 | 915 + Chestnuts, dried | 24.0 | 4.5 | 8.1 | 5.3 | 56.4| 1.7 | 1385 + Cocoanuts [F]| 48.8 | 7.2 | 2.9 | 25.9 | 14.3| 0.9 | 1295 + Cocoanut, prepared | -- | 3.5 | 6.3 | 57.4 | 31.5| 1.3 | 2865 + Filberts | 52.1 | 1.8 | 7.5 | 31.3 | 6.2| 1.1 | 1430 + Hickory nuts | 62.2 | 1.4 | 5.8 | 25.5 | 4.3| 0.8 | 1145 + Pecans, polished | 53.2 | 1.4 | 5.2 | 33.3 | 6.2| 0.7 | 1465 + Peanuts | 24.5 | 6.9 | 19.5 | 29.1 | 18.5| 1.5 | 1775 + Pinon _(Pinus edulis)_ | 40.6 | 2.0 | 8.7 | 36.8 | 10.2| 1.7 | 1730 + Walnuts, black | 74.1 | 0.6 | 7.2 | 14.6 | 3.0| 0.5 | 730 + Walnuts, English | 58.1 | 1.0 | 6.9 | 26.6 | 6.8| 0.6 | 1250 + Miscellaneous: | | | | | | | + Chocolate | -- | 5.9 | 12.9 | 48.7 | 30.3| 2.2 | 5625 + Cocoa, powdered | -- | 4.6 | 21.6 | 28.9 | 37.7| 7.2 | 2160 + Cereal coffee, infusion | | | | | | | + (1 part boiled in | | | | | | | + 20 parts water)[G] | -- | 98.2 | 0.2 | -- | 1.4| 0.2 | 30 + ============================================================================= + + +[Footnote A: Refuse, oil.] +[Footnote B: Refuse, shell.] + +[Footnote C: Plain confectionery not containing nuts, fruit, or +chocolate.] + +[Footnote D: Such vegetables as potatoes, squash, beets, etc., have a +certain amount of inedible material, skin, seeds, etc The amount varies +with the method of preparing the vegetables, and cannot be accurately +estimated The figures given for refuse of vegetables, fruits, etc., are +assumed to represent approximately the amount of refuse in these foods +as ordinarily prepared.] + +[Footnote E: Fruits contain a certain proportion of inedible materials, +as skin, seeds, etc., which are properly classed as refuse. In some +fruits, as oranges and prunes, the amount rejected in eating is +practically the same as refuse. In others, as apples and pears, more or +less of the edible material is ordinarily rejected with the skin and +seeds and other inedible portions. The edible material which is thus +thrown away, and should properly be classed with the waste, is here +classed with the refuse. The figures for refuse here given represent, as +nearly as can be ascertained, the quantities ordinarily rejected.] + +[Footnote F: Milk and shell.] + +[Footnote G: The average of five analyses of cereal coffee grain is: +Water 6.2, protein 13.3, fat 3.4, carbohydrates 72.6, and ash 4.5 per +cent. Only a portion of the nutrients, however, enter into the infusion. +The average in the table represents the available nutrients in the +beverage. Infusions of genuine coffee and of tea like the above contain +practically no nutrients.] + + + + +CHAPTER XVII + +DIETARY STUDIES + + +244. Object of Dietary Studies.--The quantity of food which different +families purchase varies between wide limits; a portion being lost +mechanically in preparation and a still larger and more variable amount +in the refuse and non-edible parts. If a record is made of all foods +purchased and the waste and non-edible portions are deducted, the +nutrients consumed by a family may be calculated by multiplying the +weight of each food by the average composition. If such calculations be +made, it will be found that in some families nearly a half pound per day +of both protein and fat is consumed by adults, while in other families +less than half of this amount is used. The object of dietary studies is +to determine the source, cost, composition, and nutritive value of the +foods consumed by different families; they also enable comparisons to be +made of the amounts of nutrients purchased. Extensive dietary studies +have been made by the United States Department of Agriculture, and the +results have been published in various bulletins.[76] + +245. Wide and Narrow Rations.--When the amount of carbohydrates in a +ration is small in comparison with the protein, it is called a narrow +ration, while a wide ration is one in which the carbohydrates are much +in excess of the protein. When a ration contains 0.40 of a pound of +protein, 0.40 of a pound of fat, and 1 pound of carbohydrates, it has a +nutritive ratio of 1 to 4.8 and is a narrow ration. To calculate the +nutritive ratio, the fat is multiplied by 2-1/4, the product added to +the carbohydrates, and this sum divided by the protein. It is not +possible to designate accurately the amount of protein and other +nutrients that should be in the daily ration of all persons, because the +needs of the body vary so with different individuals. Hard and fast +rules governing the amounts of nutrients to be consumed cannot as yet be +formulated, as our knowledge of the subject is too limited. It is known +that both excessive and scant amounts are alike injurious. While the +appetite may indicate either hunger or satiety, it alone cannot always +be relied upon as a safe guide for determining the amount and kind of +food to consume, although the demands of appetite should not be +disregarded until it has been demonstrated beyond a doubt that it is not +voicing the needs of nature. There has been a tendency which perhaps was +a survival of the Puritanical ideas of the early days to stamp as +hurtful whatever seemed desirable and pleasant; as examples might be +cited the craving for water by fever patients, and for sugar by growing +children, which have now been proven to be normal demands of nature. + +246. Dietary Standards.--As a result of a large number of dietary +studies and digestion experiments, dietary standards have been +prepared. Atwater in this country and Voit in Germany have proposed such +standards for men employed at different kinds of labor, as follows: + + + ========================================================================== + |Protein| Fat|Carbo- | Fuel |Nutritive + | | |hydrates| Value | + ---------------------------------|-------|----|-----------------|--------- + | lb. | lb.| lb. |Calories| Ratio + Man with little physical exercise| 0.20 |0.20| 0.66 | 2450 | 5.5 + Man with light muscular work | 0.22 |0.22| 0.77 | 2800 | 5.7 + Man with moderate muscular work | 0.28 |0.28| 0.99 | 3520 | 5.8 + Man with active muscular work | 0.33 |0.33| 1.10 | 4060 | 5.6 + Man with hard muscular work | 0.39 |0.55| 1.43 | 5700 | 6.9 + ========================================================================== + +In the table it will be seen that the quantity of nutrients increases +with the labor to be performed. In order to secure the necessary heat +and energy, rations for men at heavy labor contain proportionally more +fat and carbohydrates than are required for light work. All dietary +standards, however, should be regarded as tentative only. Opinions +differ greatly on different points; for example, as to the amount of +protein a ration should contain. This is a matter that can be determined +only from extended investigations under a variety of conditions, and as +yet results are too meager to formulate other than tentative standards. +Chittenden has found that the body can be sustained on very much less +protein than is called for in the standard ration.[77] The amount of +protein in the ration should be ample to sustain the body weight and +maintain a nitrogen equilibrium; that is, the income and outgo of +nitrogen from the body should be practically equal. + +[Illustration: FIG. 58.--DIETARIES AND DIETARY +STANDARDS. + +(From Office of Experiment Stations Bulletin.)] + + "While one freely admits that health and a large measure of + muscular strength may be maintained upon a minimum supply of + protein, yet I think that a dispassionate survey of mankind will + show that races which adopt such a diet are lacking in what, for + want of a better word, one can only describe as energy." [28] + +On the other hand, excessive and unnecessarily large amounts of protein +are sometimes consumed, adding greatly to the cost of the ration and +necessitating additional labor on the part of the body for its +elimination. + +247. Number of Meals per Day.--Some persons advocate two meals per day +rather than three, but dietary studies show that the best results are +secured when the food is divided among three rather than two meals, and +with a two-meal system the tendency is to consume a larger total amount +of food than when three meals are eaten. It is not essential that the +food be equally divided among the three meals. Any one of them may be +lighter or more substantial as the habits and inclinations of the +individual dictate. If it is found necessary to reduce the total +quantity of food consumed, this may be done by a proportional reduction +of each of the meals, or of any one of them instead of decreasing the +number of meals per day. The occasional missing of a meal is sometimes +beneficial, in cases of digestion disorders, but the ordinary +requirements of persons in normal health who have either mental or +physical labor to perform are best met when three meals per day are +consumed, as this insures an even supply of nutrients. For persons of +sedentary habits, the kind and quantity of food at each meal must be +regulated largely by the individual from knowledge based on personal +experience. + + "In the matter of diet every man must, in the last resort, be a law + unto himself; but he should draw up his dietetic code intelligently + and apply it honestly, giving due heed to the warnings which nature + is sure to address to him should he at any time transgress."[28] + +If there is trouble in digesting the food, it is well to study the other +habits of life along with the food question, for it may be the +difficulty arises from some other cause, and would be remedied by more +exercise and fresh air, avoiding rush immediately after meals, more +thorough mastication, or less worry. It is a serious matter to shut off +the supply of food from a person not suffering from some disease and who +is working; as well cut off the supply of fuel from a furnace and then +expect a full amount of energy and heat. But unlike the furnace, when +the human body is deprived of needed nutrients it preys upon itself and +uses up its reserve that should be drawn upon only in cases of illness +or extreme nervous strain. Some persons live in such a way as to never +have any reserve of strength and energy to call upon but use up each day +all the body can produce and so become physical bankrupts when they +should be in their prime. Food is required for the production of nerve +energy as well as physical energy.[78] + +248. Mixed Dietary Desirable.--Experiments in the feeding of farm +animals show that the best results come from the combination of a number +of foods to form a mixed ration, rather than from the use of one food +alone,[79] for in this way the work of digestion is more evenly +distributed, and a higher degree of efficiency is secured from the foods +consumed. The same is true in human feeding; the best results are +secured from a mixed diet. Ordinarily, about two fifths of the nutrients +of a ration are derived from animal and three fifths from vegetable +sources. + +249. Animal and Vegetable Foods; Economy of Production.--Animal foods +can never compete in cheapness of the nutrients with cereals and +vegetables, as it takes six to eight pounds or more of a cereal, +together with forage crops, to make a pound of meat. Hence the returns +in food value are very much larger from the direct use of the cereals as +human food, than from the feeding of cereals to cattle and the use of +the meat. As the population of a country increases, and foods +necessarily become more expensive, cereals are destined to replace +animal foods to a great extent, solely as a matter of economy. + +250. Food Habits.--Long-established dietary habits and customs are not +easily changed, and when the body becomes accustomed to certain foods, +substitution of others, although equally valuable, may fail to give +satisfactory results. For example, immigrants from southern Europe +demand foods with which they are familiar, as macaroni, olive oil, and +certain kinds of cheese, foods which are generally imported and more +expensive than the staples produced in this country,[80] and when they +are compelled to live on other foods, even though they have as many +nutrients, they complain of being underfed. Previously acquired food +habits appear to affect materially the process of digestion and +assimilation. Sudden and pronounced change in the feeding of farm +animals is attended with unsatisfactory results, and whenever changes +are made in the food of either humans or animals they should be gradual +rather than radical. + +251. Underfed Families.--As the purchasing of food is often done by +inexperienced persons, palatability rather than nutritive value is made +the basis of choice. Dietary studies show that because of lack of +knowledge of the nutritive value of foods, whole families are often +underfed. Particularly is this true where the means for purchasing foods +are limited. In dietary studies among poor families in New York +City,[81] the United States Department of Agriculture notes: "It is +quite evident that what is needed among these families more than +anything else is instruction in the way to make the little they have go +the farthest." Some classes of the rich too are equally liable to be +underfed, as they are more prone to food notions and are able to indulge +them. Among the children of the rich are found some as poorly nourished +as among the poor. + +252. Cheap and Expensive Foods.--Among the more expensive items of a +ration are meats, butter, and canned fruits. The difference in +composition and nutritive value between various cuts of meat is small, +being largely physical, and affecting taste and flavor rather than +nutritive value. Expensive cuts of meat, high-priced breakfast cereals, +tropical fruits and foods which impart special flavors, add little in +the way of nutritive value to the ration, but greatly enhance the cost +of living. Ordinarily the cheapest foods are corn meal, wheat flour and +bread, milk, beans, cheese, sugar, and potatoes.[7] The amount of animal +and vegetable foods to combine with these to form a balanced ration may +be governed largely by personal preference or cost, as there is little +difference in nutritive value. The selection of foods on the basis of +cost and nutritive value is discussed in Chapter XVI. + +253. Food Notions.--Many erroneous ideas exist as to the nutritive +value of foods, and often wholesome and valuable foods are discriminated +against because of prejudice. Skim milk is usually regarded as +containing little if any nourishing material, when in reality it has a +high protein content, and can be added to other foods to increase their +nutritive value. The less expensive cuts of meat contain more total +nutrients than many of the more expensive ones. Beef extracts have been +erroneously said to contain more nutrients than beef,[51] and mushrooms +to be equal in value of beefsteak; chemical analyses fail to confirm +either statement. The banana also has been overestimated as to food +value, and while it contains more nutrients than many fruits, it is not +the equal of cereals, as has been claimed.[82] Cocoa, although a +valuable beverage, adds but little in the way of nutrients to a ration +unless it is made with milk. The value of a food should be based upon +its composition as determined by chemical analysis, its digestibility as +founded upon digestion experiments, and its palatability and mechanical +structure. Food notions have, in many instances, been the cause of +banishing from the dietary wholesome and nutritious foods, of greatly +increasing the cost of living, as well as of promulgating incorrect +ideas in regard to foods, so that individuals and in some cases entire +families have suffered from improper or insufficient food. + +254. Dietary of Two Families Compared.--A dietary study often reveals +ways in which it is possible to improve the ration in kinds and amounts +of food, and sometimes at less expense. The following dietaries of two +families for the same period show that one family expends over twice as +much in the purchase of foods as the other family, and yet the one whose +food costs the less actually secures the larger amount of nutritive +material and is better fed than the family where more money is expended +for food.[13] + + FOOD CONSUMED, ONE WEEK + + FAMILY No. 1 + + 20 loaves of bread $1.00 + 10 to 12 lb. loin steak, or meat of similar cost 2.00 + 20 to 25 lb. rib roast, or similar meat 4.40 + 4 lb. high-priced cereal breakfast food, 20 ct. 0.80 + Cake and pastry purchased 3.00 + 8 lb. butter, 30 ct. 2.40 + Tea, coffee, spices, etc 0.75 + Mushrooms 0.75 + Celery 1.00 + Oranges 2.00 + Potatoes 0.25 + Miscellaneous canned goods 2.00 + Milk 0.50 + Miscellaneous foods 2.00 + 3 doz. eggs 0.60 + ------ + $23.45 + + FAMILY No. 2 + + 15 lb. flour, bread home-made (skim milk used) $0.45 + Yeast, shortening and skim milk 0.10 + 10 lb. steak (round. Hamburger and some loin) 1.50 + 10 lb. other meats, boiling pieces, rump roast, etc. 1.00 + 5 lb. cheese, 16 cents 0.80 + 5 lb. oatmeal (bulk) 0.15 + 5 lb. beans 0.25 + Home-made cake and pastry 1.00 + 6 lb. butter, 30 ct. 1.80 + 3 lb. home-made shortening 0.25 + Tea, coffee, and spices 0.40 + Apples 0.50 + Prunes 0.25 + Potatoes 0.25 + Milk 1.00 + Miscellaneous foods 1.00 + 3 doz. eggs 0.60 + ------ + $11.30 + +[Illustration: FIG. 59.--COST AND NUTRITIVE VALUE OF RATIONS.] + +In comparing the foods used by the two families, it will be observed +that family No. 1 purchased their bread at the bakery at a cost of $ +1.00, while the bread of family No. 2 was home-made, skim milk being +used in its preparation, the flour, milk, yeast, and shortening costing +about 55 cents. Family No. 1 consumed 10 pounds of expensive steaks, +family No. 2 consumed the same number of pounds, a portion being cheaper +cuts. Instead of the 20 pounds of roast or similar beef used by family +No. 1, only one half as much and cheaper cuts as boiling pieces, stew, +rump roast, etc., were used by family No. 2; 5 pounds of beans and 5 +pounds of cheese taking the place of some of the meat. Family No. 1 +consumed 4 pounds of high-priced cereal breakfast foods, supposing they +contained a larger amount of nutrients than were actually present. In +place of the 4 pounds of high-priced cereal breakfast foods of family +No. 1, family No. 2 used 5 pounds of oatmeal purchased in bulk. Family +No. 1 bought their cake and pastry for $3.00, while those of family No. +2 were home made and cost $1.00. Family No. 2 used 2 pounds less butter +per week because of the preparation and use of home-made shortening from +beef suet and milk. They also purchased a smaller amount of tea, coffee, +and spices than family No. 1. Family No. 2 consumed a larger quantity of +less expensive fruits and vegetables than family No. 1, who ate 75 +cents' worth of mushrooms with the idea that they contained as much +protein as meat, but analyses show that mushrooms contain no more +nutrients than potatoes and similar vegetables. In place of the celery +and oranges, apples and prunes were used by family No. 2. The same +amount of potatoes was used by each. Fifty cents was spent for milk by +family No. 1 and $1.00 by family No. 2. The total amount expended for +food by family No. 1 was $23.45, while family No. 2 purchased a greater +variety of foods for $11.30, as well as foods containing more nutrients. +The approximate amounts of nutrients in the foods purchased by the two +families are given in the following table, from which it will be +observed that family No. 2 obtained a much larger amount of total +nutrients and was better fed at considerably less expense than family +No. 1. + +NUTRIENTS IN FOODS CONSUMED.--FAMILY NO. 1 + + ============================================= + |PROTEIN| FAT |CARBOHYDRATES + | LB. | LB. | LB. + -------------------------|-----|------------- + 20 lb. bread | 1.98 | 0.28| 11.42 + 10 lb. loin steak| 1.59 | 1.76| -- + 20 lb. rib roast | 2.68 | 4.26| -- + 4 lb. cereals | 0.42 | 0.06| 2.75 + 8 lb. butter | 0.04 | 6.80| -- + 25 lb. potatoes | 0.45 | 0.03| 3.83 + 20 lb. milk | 0.70 | 0.80| 1.00 + |-------|-----|------------- + | 7.86 |13.99| 19.00 + ============================================= + + FAMILY NO. 2 + ===================================================== + |PROTEIN| FAT |CARBOHYDRATES + | LB. | LB. | LB. + -------------------------|-------|-----|------------- + 15 lb. flour | 1.89 | 0.12| 11.15 + 5 lb. skim milk | 0.16 | 0.01| 0.26 + 10 lb. round steak | 1.81 | 1.26| -- + 10 lb. beef | 1.32 | 2.02| -- + 5 lb. cheese | 1.40 | 1.75| -- + 5 lb. oatmeal | 0.78 | 0.36| 3.40 + 6 lb. butter | 0.03 | 5.10| -- + 3 lb. shortening | -- | 2.55| -- + 3 lb. prunes | 0.03 | -- | 0.60 + 25 lb. apples | 0.12 | -- | 2.50 + 25 lb. potatoes | 0.45 | 0.03| 3.83 + 40 lb. milk | 1.44 | 1.60| 1.90 + 5 lb. beans | 1.12 | -- | 3.00 + -------------------------|-------|-----|------------------ + | 10.55 |14.80| 26.64 + -------------------------|-------|-----|------------------ + Difference in nutrients | + in favor of family No. 2,| + consuming the cheaper |2.69 0.81 7.64 + combination of foods | + ===================================================== + +255. Food in its Relation to Mental and Physical Vigor.--When the body +is not properly supplied with food, the best results in the form of +productive work cannot be secured. There is a close relationship between +the nature of the food consumed and mental activity, also ability to +satisfactorily perform physical labor. "The productive power of the +individual as well as of the nation depends doubtless upon many factors +other than food, such as race, climate, habit, etc., but there is no +gainsaying the fact that diet has also a profound and direct influence +upon it."[83] + +If the body is diseased, it cannot make the right uses of the food, and +often the food is blamed when the trouble is due primarily to other +causes. The fact that a diseased digestive tract is unable to utilize +some foods is no valid reason why these foods should be discarded in the +dietary of persons in normal health, particularly when the food is in no +way responsible for the disease. + +Some diseases are most prevalent in the case of a restricted diet. A +change in the dietary of the Japanese navy greatly improved the health +of the sailors. + + "The prevalence of kakke or beriberi in the navy turned the + attention of many medical specialists toward the problem of + nutrition.... It was generally believed that there was some very + close connection between the disease and the rice diet.... One + outcome of these investigations was the passage of the food supply + act of the navy in 1884. The ration provided in accordance with + this act was sufficient to furnish an abundance of protein and + energy.... Following the change of ration in 1884, the prevalence + of the disease was very materially diminished, and at the end of + three years cases of kakke were practically unknown among the + marines."[83] + +256. Dietary Studies in Public Institutions.--Dietary studies in +public institutions, as prisons, and asylums for the insane, show that +it is possible to secure greater variety of food containing a larger +amount of nutrients, and even at a reduction in cost.[84] In such +institutions it is important that the food should be not only ample in +amount, but wholesome and nutritious, as many of the inmates respond +both physically and mentally to an improved diet. For humanitarian as +well as economic reasons institutional dietetics should more generally +be placed under the supervision of skilled dietists. + + + + +CHAPTER XVIII + +RATIONAL FEEDING OF MAN + + +257. Object.--Rational feeding of man has for its object the +regulation of the food supply in accord with the demands of the body. It +is based upon the same principles as the rational feeding of animals; in +each, the best results in the way of health, amount of labor performed, +and economy are secured when the body receives nutrients sufficient for +the production of heat and energy and for the repair of worn-out +tissues. Rational feeding is simply regulation of the food, both as to +kind and amount, to meet the needs of the body.[72] + +258. Standard Rations.--In human feeding, as in animal feeding, it is +not possible to lay down hard and fast rules as to the quantity of +nutrients required for a standard ration.[85] As stated in the chapter +on Dietary Studies, such standards have been proposed, but they are to +be considered as tentative rather than absolute, for the amount of food +required by different persons must necessarily vary with the +individuality. While it is impossible to establish absolute standards, +any large variation from the provisional standards usually results in +lessened ability to accomplish work, ill health, or increased expense. + +259. Amounts of Food Consumed.--The approximate amounts of some food +articles consumed per day are as follows: + + =================================== + | RANGE | APPROXIMATE + | |AMOUNT IN LBS. + --------|-------------------------- + Bread |6 to 14 oz.| 0.50 + Butter |2 to 5 oz.| 0.12 + Potatoes|8 to 16 oz.| 0.75 + Cheese |1 to 4 oz.| 0.12 + Beans |1 to 4 oz.| 0.12 + Milk |8 to 32 oz.| -- + Sugar |2 to 5 oz.| 0.20 + Meats |4 to 12 oz.| 0.25 + Oatmeal |1 to 4 oz.| 0.12 + =================================== + +In the calculation of rations it is desirable that the amount of any +food article should not exceed that designated, unless for some special +reason it has been found the food can consistently be increased. The +amount of nutrients given in dietary standards is for one day, and the +nutrients may be divided among the three meals as desired. It is to be +noted that, ordinarily, the foods which supply carbohydrates are flour, +corn meal, cereal products, potatoes, beans, sugar, and milk; those +which supply fat are milk, butter, lard, and meats; and those which +supply protein in liberal amounts are beans, cheese, meats, oatmeal, +cereals, bread, and milk. + +260. Average Composition of Foods.--The amounts of nutrients in foods +are determined from the average composition of the foods. These figures +for average composition are based upon analyses of a large number of +samples of food materials.[7] In individual cases it will be found that +foods may vary from the standards given; as for example, milk may +contain from 2.5 to 5 per cent of fat, while the protein and fat of +meats vary appreciably from the figures given for average composition. +With the cereals and vegetable foods, variations from the standards are +small. In the table, the composition of the food as purchased represents +all of the nutrients in the food, including those in the refuse, +trimmings, or waste, while the figures for the edible portion represent +the nutrients in the food after deducting what is lost as refuse. In +making calculations, the student should use the figures given for the +foods as purchased, unless the weights are of the edible portion only. +The figures in the table are on the basis of percentage amounts, or +nutrients in 100 pounds of food. By moving the decimal point two places +to the left, the figures will represent the nutrients in one pound, and +if this is multiplied by the number of pounds or fraction of a pound +used, the quantity of nutrients is secured. For example, suppose bread +contains 9.5 per cent of protein and 56 per cent of carbohydrates, 1 +pound would contain 0.095 pound of protein, 0.56 pound of +carbohydrates; and 0.5 of a pound would contain approximately 0.05 pound +of protein and 0.28 pound of carbohydrates. In calculating rations, it +is not necessary to carry the figures to the third decimal place. + +[Illustration: FIG. 60.--FOOD ARTICLES FOR A HUMAN RATION.] + +261. Example of a Ration.--Suppose it is desired to calculate a ration +for a man at light muscular work. First, note the requirements in the +way of nutrients in the table "Dietary Standards," Section 246. Such a +ration should supply approximately 0.22 pound each of protein and fat, +and 0.77 pound of carbohydrates, and should yield 2800 calories. A trial +ration is made by combining the following: + + ========================================================== + | Pound + Bread | 0.50 + Butter | 0.12 + Potatoes | 0.75 + Milk | 1.00 + Sugar | 0.12 + Beef | 0.25 + Ham | 0.20 + Oatmeal | 0.12 + Eggs | 0.25 + ========================================================== + +The quantities of nutrients in these food materials are approximately as +follows: + + +RATION FOR MAN AT MODERATE WORK + + =================================================================== + | | PROTEIN | FAT | C.H. | + | LB. | LB. | LB. | LB. | CALORIES + -------------------------+------+---------+------+------+---------- + Bread | 0.50 | 0.05 | 0.01 | 0.29 | 653 + Butter | 0.12 | -- | 0.10 | -- | 432 + Potato | 0.75 | 0.01 | -- | 0.12 | 244 + Milk | 1.00 | 0.04 | 0.04 | 0.05 | 323 + Sugar | 0.12 | -- | -- | 0.12 | 192 + Beef (round) | 0.25 | 0.05 | 0.03 | -- | 218 + Ham | 0.20 | 0.03 | 0.07 | -- | 331 + Oatmeal | 0.12 | 0.02 | 0.01 | 0.08 | 223 + Eggs | 0.25 | 0.03 | 0.03 | -- | 164 + Squash | 0.20 | -- | -- | 0.01 | 25 + |------+---------+------+------+---------- + | | 0.23 | 0.29 | 0.67 | 2805 + =================================================================== + +It is to be noted that this ration contains approximately the amount of +protein called for in the standard ration, while the fat is slightly +more and the carbohydrates are less. The food value of the ration is +practically that called for in the standard. This ration is sufficiently +near the standard to supply the nutrient requirements of a man at light +muscular work. To supply palatability, some fruit and vegetables should +be added to the ration. These will contribute but little to the nutrient +content, but are necessary in order to secure health and the best +returns from the other foods, and as previously stated, they are not to +be estimated entirely upon the basis of nutrient content. A number of +food articles could be substituted in this ration, if desired, either in +the interests of economy, palatability, or personal preference. + +262. Requisites of a Balanced Ration.--Reasonable combinations of +foods should be made to form balanced rations.[2] A number of foods slow +of digestion, or which require a large amount of intestinal work, should +not be combined; neither should foods which are easily digested and +which leave but little indigestible residue. After a ration has been +calculated and found to contain the requisite amount of nutrients, it +should be critically examined to see whether or not it fulfills the +following requirements: + + 1. Economy and adaptability to the work required. + + 2. Necessary bulk or volume. + + 3. Desired physiological influence of the foods upon the digestive + tract, whether constipating or laxative in character. + + 4. Ease of digestion. + + 5. Effect upon health. It is recognized that there are foods + wholesome and nutritious, that cannot be used by some persons, + while with others the same foods can be consumed with impunity. + +As explained in the chapter on Dietary Studies, the nutrients should be +supplied from a number of foods rather than from a few, because it is +believed the various nutrients, particularly the proteins, are not +absolutely identical from all sources, or equal in nutritive value. + + +EXAMPLES + +1. Calculate a ration for a man with little physical exercise. + +2. Calculate a ration for a man at hard muscular labor, and give the +approximate cost of the ration. + +3. Calculate the amounts of food and the nutrient requirements for a +family of seven for 10 days; five of the family to consume 0.8 as much +as an adult. Calculate the cost of the food; then calculate on the same +basis the probable cost of food for one year, adding 20 per cent for +fluctuation in market price and additional foods not included in the +list. + +4. Weigh out the food articles used in problem No. 2, and apportion them +among three meals. + + + + +CHAPTER XIX + +WATER + + +263. Importance.--Water is one of the most essential food materials. +It enters into the composition of the body, and without it the nutrients +of foods would be unavailable, and life could not be sustained. Water +unites chemically with various elements to form plant tissue and +supplies hydrogen and oxygen for the production of organic compounds +within the leaves of plants. In the animal economy it is not definitely +known whether or not water furnishes any of the elements of which the +tissues are composed, as the food contains liberal amounts of hydrogen +and oxygen; it is necessary mainly as the vehicle for distributing +nutrients in suspension and solution, and as a medium in which chemical, +physical, and physiological changes essential to life processes take +place. From a sanitary point of view, the condition of the water supply +is of great importance, as impure water seriously affects the health of +the consumer.[87] + +264. Impurities in Water.--Waters are impure because of: (1) excessive +amounts of alkaline salts and other mineral compounds; (2) decaying +animal and vegetable matters which act chemically as poisons and +irritants, and which may serve as food for the development of +objectionable bacterial bodies; and (3) injurious bacteria. The most +common forms of impurities are excess of organic matter and bacterial +contamination. The sanitary condition of water is greatly influenced by +the character of the soil through which it flows and the extent to which +it has been polluted by surface drainage.[88] + +[Illustration: FIG. 61.--DIRT AND IMPURITIES IN A SURFACE WELL WATER.] + +265. Mineral Impurities.--- The mineral impurities of water are mainly +soluble alkaline and similar compounds dissolved by the water in passing +through various layers of soil and rock. When water contains a large +amount of sodium chloride, sodium sulphate or carbonate, or other +alkaline salts, it is termed an "alkali water." Where water passes +through soil that has been largely formed from the decay of rocks +containing alkaline minerals, the water dissolves some of these minerals +and becomes alkaline. The kind of alkali determines the character of the +water; in some cases it is sodium carbonate, which is particularly +objectionable. The continued use of strong alkali water causes digestion +disorders, because of the irritating action upon the digestive tract. +Hard waters are due to the presence of lime compounds. In regions where +limestone predominates, the carbon dioxid in water acts as a solvent, +producing hard waters. Waters that are hard on account of the presence +of calcium carbonate give a deposit when boiled, due to liberation of +the carbon dioxid which is the material that renders the lime soluble. +Calcium sulphate, or gypsum, on the other hand, imparts permanent +hardness. There is no deposit when such waters are boiled. A large +number of minerals are found in various waters, often sufficient in +amount to impart physiological properties. Water that is highly charged +with mineral matter is difficult to improve sufficiently for household +purposes. About the only way is by distillation.[89] + +266. Organic Impurities.--Water that flows over the surface of the +ground comes in contact with animal and vegetable material in various +stages of decay, and as a result some is dissolved and some is +mechanically carried along by the water. After becoming soluble, the +organic matter undergoes further chemical changes, as oxidation and +nitrification caused by bacteria. If the organic matter contain a large +amount of nitrogenous material, particularly of proteid origin, a series +of chemical changes induced by bacterial action takes place, resulting +in the production of nitrites. The nitrifying organisms first produce +nitrous acid products (nitrites), and in the further development of the +nitrifying process these are changed to nitrates. The ammonia formed as +the result of the decomposition of nitrogenous organic matter readily +undergoes nitrification changes. Nitrates and nitrites alone are not +injurious in water, but they are usually associated with objectionable +bacteria and generally indicate previous contamination.[90] + +267. Interpretation of a Water Analysis.--"Total solid matter" +represents all the mineral, vegetable, and animal matter which a water +contains. It is the residue obtained by evaporating the water to dryness +at a temperature of 212 deg. F. Average drinking water contains from 20 to +90 grains per gallon of solid matter. "Free ammonia" is that formed as a +result of the decomposition of animal or vegetable matter containing +nitrogen. Water of high purity usually contains less than 0.07 parts +per million of free ammonia. "Albuminoid ammonia" is derived from the +partially decomposed animal or vegetable material in water. The greater +the amount of nitrogenous organic impurities, the higher the albuminoid +ammonia. A good drinking water ought not to contain more than 0.10 part +per million of albuminoid ammonia. An abnormal quantity of chlorine +indicates surface drainage or sewage contamination, or an excess of +alkaline matter, as common salt. Nitrites should not be present, as they +are generally associated with matter not completely oxidized. Nitrites +are usually considered more objectionable than nitrates; both are +innocuous unless associated with disease-producing nitrooerganisms. + +268. Natural Purification of Water.--River waters are sometimes dark +colored because of large amounts of dissolved organic matter, but in +contact with the sun and air they gradually undergo natural purification +and the organic matter is oxidized. However, absolute reliance cannot be +placed upon natural purification of a bad water, as the objectionable +organisms often have great resistive power. There is no perfectly pure +water except that prepared in the chemical laboratory by distillation. +All natural waters come in contact with the soil and air, and +necessarily contain impurities proportional to the extent of their +contamination. + +269. Water in Relation to Health.--There are many diseases, of which +typhoid fever is a type, that are distinctly water-born. The typhoid +bacilli, present in countless numbers in the feces of persons suffering +or convalescent from typhoid fever, find their way into streams, lakes, +and wells.[91] They retain their vitality, and when they enter the +digestive tract of an individual, rapidly increase in numbers. Numerous +disastrous outbreaks of typhoid fever have been traced to contamination +of water. Coupled with the sanitary improvement of a city's water +supply, there is diminution of typhoid fever cases, and a noticeable +lowering of the death rate. Many cities and villages are dependent for +their water upon rivers and lakes into which surface drainage finds its +way, with all contaminating substances. Mechanical sedimentation and +filtration greatly improve waters of this class, but do not necessarily +render them entirely pure. Compounds of iron and aluminium are sometimes +added in small amounts, under chemical supervision, to such waters to +precipitate the organic impurities. Spring waters are not entirely above +suspicion, as oftentimes the soil through which they flow is highly +polluted. All water of doubtful purity should be boiled, and there are +but few natural waters of undoubted purity. There is no such thing as +absolutely pure water in a state of nature. The mountain streams perhaps +approach nearest to it where there are no humans to pollute the banks; +but then there are always the beasts and birds, and they, too, are +subject to disease. There are very few waters that at some time of the +year and under some conditions are not contaminated with +disease-producing organisms. No matter how carefully guarded are the +banks of lakes furnishing the water supply of cities, more or less +objectionable matter will get in. In seasons of heavy rains, large +amounts of surface water enter the lakes, carrying along the filth +gathered from many acres of land drained by the streams entering the +lakes. Some of the most serious outbreaks of typhoid fever have come +from temporary contamination of ordinarily fairly good drinking water. +In general, too little attention is given to the purity of drinking +water. It is just as important that water should be boiled as that food +should be cooked. One of the objects of cooking is to destroy the +injurious bacteria, and they are frequently more numerous in the +drinking water than in the food. + +The argument is sometimes advanced that the mineral matter present in +water is needed for the construction of the bone and other tissues of +the body, and that distilled water fails to supply the necessary mineral +matter. This is an erroneous assumption, as the mineral matter in the +food is more than sufficient for this purpose. When water is highly +charged with mineral salts, additional work for their elimination is +called for on the part of the organs of excretion, particularly the +kidneys; and furthermore, water nearly saturated with minerals cannot +exert its full solvent action. + +In discussing the immediate benefits resulting from improvement of +water, Fuertes says:[92] + + "Immediately after the change to the 'four mile intake' at Chicago + in 1893, there was a great reduction in typhoid. Lawrence, Mass., + showed a great improvement with the setting of the filters in + operation in September, 1893; fully half of the deaths in 1894 were + among persons known to have used the unfiltered canal water. The + conclusion is warranted that for the efficient control of the death + rate from typhoid fever it is necessary to have efficient sewerage + and drainage, proper methods of living, and pure water. The reason + why our large cities, which are all provided with sewerage, have + such high death rates is therefore without doubt their continuance + of the filthy practice of supplying drinking water which carries in + solution and suspension the washings from farms, from the streets, + from privies, from pigpens, and the sewage of cities.... And also + we should recognize the importance of flies and other winged + insects and birds which feed on offal as carriers of bacteria of + specific diseases from points of infection to the watersheds, and + the consequent washing of newly infected matter into our drinking + water by rains." + +There is a very close relationship between the surface water and that of +shallow wells. A shallow well is simply a reservoir for surface water +accumulations. It is stated that, when an improved system of drainage +was introduced into a part of London, many of the shallow wells became +dry, indicating the source from which they received their supply. Direct +subterranean connection between cesspools and wells is often traced in +the following way: A small amount of lithium, which gives a distinct +flame reaction, and a minute trace of which can be detected with the +spectroscope, is placed in the cesspool, and after a short time a +lithium reaction is secured from the well water. + +Rain water is relied upon in some localities for drinking purposes. That +collected in cities and in the vicinity of barns and dwellings contains +appreciable amounts of organic impurities. The brown color is due to the +impurities, ammonium carbonate being one of these. There are also traces +of nitrates and nitrites obtained from the air. When used for drinking, +rain water should be boiled. + +270. Improvement of Waters.--Waters are improved by: (1) boiling, +which destroys the disease-producing organisms; (2) filtration, which +removes the materials mechanically suspended in the water; and (3) +distillation, which eliminates the impurities in suspension and +solution, as well as destroys all germ life. + +271. Boiling Water.--In order to destroy the bacteria that may be in +drinking water, it is not sufficient to heat the water or merely let it +come to a boil. It has been found that if water is only partially +sterilized and then cooled in the open air, the bacteria develop more +rapidly than if the water had not been heated at all. It should boil +vigorously five to ten minutes; cholera and typhoid bacteria succumb in +five minutes or less. Care should be taken in cooling that the water is +not exposed to dust particles from the air nor placed in open vessels in +a dirty refrigerator. It should be kept in perfectly clean, +tight-stoppered bottles. These bottles should be frequently scalded. +Great reliance may be placed upon this method of water purification when +properly carried out. + +272. Filtration.--Among the most efficient forms of water filters are +the Berkefeld and Pasteur. The Pasteur filter is made of unglazed +porcelain, and the Berkefeld of fine infusorial earth (finely divided +SiO_{2}). Both are porous and allow a moderately rapid flow of water. +The flow from the Berkefeld filter is more rapid than from the Pasteur. +The mechanical impurities of the water are deposited upon the filtering +surface, due to the attraction which the material has for particles in +suspension. These particles usually are the sources of contamination and +carry bacteria. When first used, filters are satisfactory, but unless +carefully looked after they soon lose their ability to remove germs from +the water and may increase the impurity by accumulation. Small faucet +filters are made of porous stone, asbestos, charcoal, etc. Many of them +are of no value whatever or are even worse than valueless. Filters +should be frequently cleansed in boiling water or in steam under +pressure. Unless this is done, the filters may become incubators for +bacteria. + +[Illustration: FIG. 62.--PASTEUR WATER FILTERS.] + +273. Distillation.--When an unquestionably pure water supply is +desired, distillation should be resorted to. There are many forms of +stills for domestic use which are easily manipulated and produce +distilled water economically.[93] The mineral matter of water is in no +way essential for any functional purpose, and hence its removal through +distillation is not detrimental. + +[Illustration: FIG. 63.--WATER STILL.] + +274. Chemical Purification.--Purification of water by the use of +chemicals should not be attempted in the household or by inexperienced +persons. When done under supervision of a chemist or bacteriologist, it +may be of great value to a community. Turneaure and Russell,[94] in +discussing the purification of water by addition of chemicals, state: + + "There are a considerable number of chemical substances that may be + added to water in order to purify it by carrying down the suspended + matter as well as bacteria, by sedimentation. Such a process of + purification is to be seen in the addition of alum, sulphate of + iron, and calcium hydrate to water. Methods of this character are + directly dependent upon the flocculating action of the chemical + added, and the removal of the bacteria is accomplished by + subsidence." + +275. Ice.--The purity of the ice supply is also of much importance. +While freezing reduces the number of organisms and lessens their +vitality, it does not make an impure water absolutely wholesome. The +way, too, in which ice is often handled and stored subjects it to +contamination, and foods which are placed in direct contact with it +mechanically absorb the impurities which it contains. For cooling water, +ice should be placed around rather than in it. Diseases have frequently +been traced to impure ice. The only absolutely pure ice is that made +from distilled water. + +276. Mineral Waters.--When water is charged with carbonic acid gas +under pressure, carbonated water results, and when minerals, as salts of +sodium, potassium, or lithium, are added, artificial mineral waters are +produced. Natural mineral waters are placed on the market to some +extent, but most mineral waters are artificial products and they are +sometimes prepared from water of low sanitary character. Mineral waters +should not be used extensively except under medical direction, as many +have pronounced medicinal properties. Some of the constituents are +bicarbonates of sodium, potassium, and lithium; sulphates of magnesium +(Epsom salts) and calcium; and chloride of sodium. The sweetened mineral +waters, as lemonade, orangeade, ginger ale, and beer, contain sugar and +organic acids, as citric and tartaric, and are flavored with natural or +artificial products. Most of them are prepared without either fruit or +ginger. Natural mineral waters used under the direction of a physician +are often beneficial in cases of chronic digestion disorders or other +diseases. + +277. Materials for Softening Water.--The materials most commonly used +for softening water are sodium carbonate (washing soda), borax, ammonia, +ammonium carbonate, potash, and soda lye. Waters that are very hard with +limestone should have a small amount of washing soda added to them. Two +ounces for a large tub of water is the most that should be used, and it +should first be dissolved in a little water. If too much soda is used, +it is injurious, as only a certain amount can be utilized for softening +the water, and the excess simply injures the hands and fabric. When hard +limewater is boiled and a very little soda lye added, a precipitate of +carbonate of lime is formed, and then if the water is strained, it is +greatly improved for washing purposes. Borax is valuable for making some +hard waters soft. It is not as strong in its action as is sodium +carbonate. For the hardest water 1/4 pound of borax to a large tubful +may be used; most waters, however, do not need so much. Ammonia is one +of the most useful reagents for softening water. It is better than +washing soda and borax, because the ammonia is volatile and does not +leave any residue to act on the clothes, thus causing injury. For +bathing purposes, the water should be softened with ammonia, in +preference to any other material. Ammonia should not be poured directly +into hot water; it should be added to the water while cold, or to a +small quantity of cold water, and then to the warm water, as this +prevents the ammonia from vaporizing too readily. Ammonia produces the +same effect as potash or soda lye, without leaving a residue in the +garments washed. It is especially valuable in washing woolen goods or +materials liable to shrink. Waters which are hard with alum salts are +greatly benefited by the addition of ammonia. A little in such a water +will cause a precipitate to form, and when the water is strained it is +in good condition for cleaning purposes. Ammonium carbonate is used to +some extent as a softening and cleaning agent, and is valuable, as there +is no injurious effect upon clothing, because it readily volatilizes. +Caustic potash and caustic soda are sometimes employed for softening +water, but they are very active and are not adapted to washing colored +or delicate fabrics. They may be used for very heavy and coarse articles +that are greasy,--not more than a gram in a gallon of water. Bleaching +powder is not generally a safe material for cleansing purposes, as it +weakens the texture of clothing. After a contagious disease, articles +may be soaked in water containing a little bleaching powder and a few +drops of carbolic acid, followed by thorough rinsing and bleaching in +the sun. But as a rule formaline is preferable for disinfecting +clothing. It can be used at the rate of about one pound to 100 gallons +of water. Bleaching powder, caustic potash or soda, and strong soap are +not suitable for cleaning woodwork, because of the action of the alkali +on paint and wood; they roughen the surface and discolor the paint. +Waters vary so in composition, that a material suitable for softening +one may not prove to be the best for softening another. The special kind +must be determined largely by trial, and it should be the aim to use as +little as possible. When carbolic acid, formaline, bleaching powder, and +caustic soda are used, the hands should be protected and the clothes +should be well rinsed. + +[Illustration: FIG. 64.--TYPHOID BACILLI.] + +278. Economic Value of a Pure Water Supply.--From a financial point of +view, the money spent in securing pure water is one of the best +investments a community can make. Statisticians estimate the death of an +adult results in a loss to the state of from $1000 to $5000; and to the +losses sustained by death must be added those incurred by sickness and +by lessened quality and quantity of work through impaired +vitality,--all caused by using poor drinking water. Wherever plants have +been installed for improving the sanitary condition of the water supply, +the death rate has been lowered and the returns to the community have +been far greater than the cost of the plant. Impure water is the most +expensive food that can be consumed. + + + + +CHAPTER XX + +FOOD AS AFFECTED BY HOUSEHOLD SANITATION AND STORAGE + + +279. Injurious Compounds in Foods.--An ordinary chemical analysis of a +food determines only the nutrients, as protein, carbohydrates, and fats; +and unless there is reason to believe the food contains injurious +substances no special tests for these are made. There are a number of +poisonous compounds that foods may contain, and many of them can but +imperfectly be determined by chemical analysis. Numerous organic +compounds are produced in foods as the result of the workings of +microoerganisms; some of these are poisonous, while others impart only +special characteristics, as taste and odor. The poisonous bacteria +finding their way into food produce organic compounds of a toxic +character; and hence it is that the sanitary condition of a food, as +influenced by preparation and storage, is often of more vital importance +than the nutrient content.[95] + +[Illustration: FIG. 65.--TUBERCULOSIS BACILLI. (After CONN.) + +Often present in dust particles and contaminated foods.] + +280. Sources of Contamination of Food.--As a rule, too little +attention is given to the sanitary handling and preparation of foods. +They are often exposed to impure air and to the dust and filth from +unclean streets and surroundings, and as a result they become inoculated +with bacteria, which are often the disease-producing kind. Gelatine +plates exposed by bacteriologists under the same conditions as foods +develop large numbers of injurious microoerganisms. In order to avoid +contamination in the handling of food, there must be: (1) protection +from impure air and dust; (2) storage in clean, sanitary, and ventilated +storerooms and warehouses; (3) storage of perishable foods at a low +temperature so as to retard fermentation changes; and (4) workmen free +from contagious diseases in all occupations pertaining to the +preparation of foods. Ordinarily, foods should not be stored in the +paper wrappers in which they are purchased, as unclean paper is often a +source of contamination. + +281. Sanitary Inspection of Food.--During recent years some state and +city boards of health have introduced sanitary inspection of foods, with +a view of preventing contamination during manufacture and +transportation, and this has done much to improve the quality and +wholesomeness. Putrid meats, fish, and vegetables are not allowed to be +sold, and foods are required to be handled and stored in a sanitary way. +Next to a pure water supply, there is no factor that so greatly +influences for good the health of a community as the sanitary condition +of the food. While the cooking of foods destroys many organisms, it +often fails to render innocuous the poisons which they produce, and +furthermore the unsound foods when cooked are not entirely wholesome, +and they have poor keeping qualities. + +Often meats, vegetables, and other foods eaten uncooked, as well as the +numerous cooked foods, are exposed in dirty market places, and +accumulate large amounts of filth, and are inoculated with disease germs +by flies. Protection of food from flies is a matter of vital importance, +as they are carriers of many diseases. In the case of typhoid fever, +next to impure drinking water flies are credited with being the greatest +distributors of the disease germs.[96] + +[Illustration: FIG. 66.--DIPHTHERIA BACILLI. (After CONN.) + +Often present in dust particles and in food unprotected from dust.] + +282. Infection from Impure Air.--The dust particles of the air contain +decayed animal and vegetable matter in which bacteria are present; these +find their way into the food when it is not carefully protected, into +the water supply, and also into the lungs and other organs of the body. +When foods are protected from the mechanical impurities which gain +access through the air, and fermentation is delayed by storage at a low +temperature, digestion disorders are greatly lessened. From a sanitary +point of view, the air of food storerooms and of living rooms should be +of equally high purity. When foods are kept in unventilated living +rooms, they become contaminated with the impurities thrown off from the +lungs in respiration, which include not only carbon dioxid, but the more +objectionable toxic organic materials. + +Vegetable foods need to be stored in well-ventilated places, as the +plant cells are still alive and carrying on life functions, as the +giving off of carbon dioxid, which is akin to animal respiration; in +fact, it is plant-cell respiration. Provision should be made for the +removal of the carbon dioxid and other products, as they contaminate the +air. When vegetable tissue ceases to produce carbon dioxid, death and +decay set in, accompanied by fermentation changes. + +283. Storage of Food in Cellars.--Cellars are often in a very +unsanitary condition, damp, poorly lighted, unventilated, and the air +filled with floating particles from decaying vegetables. The walls and +shelves absorb the dust and germs from the foul air and are bacterially +contaminated, and whenever a sound food is stored in such a cellar, it +readily becomes inoculated with bacteria. There is a much closer +relationship existing between the atmosphere of the cellar and that of +the house than is generally realized. An unclean cellar means +contaminated air throughout the house. When careful attention is given +to the sanitary condition of the cellar, many of the more common +diseases are greatly reduced. Cases of rheumatism have often been traced +to a damp cellar. In some localities where the cellars are unusually +unsanitary, there is in the season of spring rains, when they are +especially damp and contain the maximum of decayed vegetation, a +prevalence of what might be called "cellaritis." The symptoms differ and +the trouble is variously attributed, but the real cause is the same, +although overlooked, for, unfortunately, doctors do not visit the +cellar. + +Cellars should be frequently cleaned and disinfected, using for the +purpose some of the well-known disinfectants, as formaline, bleaching +powder, or a dilute solution of carbolic acid. It has been found in +large cities, when the spread of such diseases as yellow fever was +imminent, that a general and thorough cleaning up of streets and cellars +with the improved sanitary conditions resulting greatly lowered the +usual death rate. + +[Illustration: Fig. 67.--DUNG FUNGUS. (After BUTTERS.) + +Often present on surface of unclean vegetables.] + +284. Sunlight, Pure Water, and Pure Air as Disinfectants.--The most +effectual and valuable disinfectants are sunlight, pure water, and pure +air. Many kinds of microoerganisms, particularly those that are +disease-producing, are destroyed when exposed for a time to sunlight. +The chemical action of the sun's rays is destructive to the organic +material which makes up the composition of many of these organisms, +while higher forms of organic life are stirred into activity by it. The +disinfecting power of sunlight should be made use of to the fullest +extent, not only in the house, but plenty of sunlight should also be +planned for in constructing barns and other buildings where milk-and +meat-producing animals are kept. Pure water is also a disinfectant, but +when water becomes polluted it loses this power. Many disease-producing +organisms are rendered inactive when placed in pure water. Water +contains more dissolved oxygen than air, and apparently a portion of the +oxygen in water is in a more active condition than that in air. Pure +air, too, is a disinfectant; the ozone and hydrogen peroxide and oxides +of nitrogen, which are present in traces, exert a beneficial influence +in oxidizing organic matter. Fresh air and sunlight, acting jointly, are +nature's most effectual disinfectants. Sunshine, fresh air, and pure +water are a health-producing trinity. In discussing the importance of +pure air, water, and sunlight, Ellen H. Richards[97] says: + + "The country dweller surrounds his house with evergreens or shade + trees, the city dweller is surrounded with high brick walls. + Blinds, shades, or thick draperies shut out still more, and prevent + the beneficial sunlight from acting its role of germ prevention and + germ destruction. Bright-colored carpets and pale-faced children + are the opposite results which follow. Sunlight, pure air, and pure + water are our common birthright which we often bargain away for + so-called comforts." + +And Dr. Woods Hutchinson says of sunlight: + + "It is a splendid and matchless servant in the promoting of + healthfulness of the house, for which no substitute has yet been + discovered. It is the foe alike of bacilli and the blues; the best + tonic ever yet invented for the liver and for the scalp, and for + everything between, the only real complexion restorer, and the + deadliest foe of dirt and disease." + +[Illustration: FIG. 68.--DIRT AND MANURE EMBEDDED IN SURFACE OF CELERY.] + +285. Utensils for Storage of Food.--In order that dishes and household +utensils may be kept in the best sanitary condition, they should be free +from seams, cracks, and crevices where dust and dirt particles can find +lodgment. From the seams of a milk pail that has not been well washed, +decaying milk solids can be removed with the aid of a pin or a +toothpick. This material acts as a "starter" or culture when pure, fresh +milk is placed in the pail, contaminating it and causing it to become +sour. Not only is this true of milk, but also of other foods. Wooden +utensils are not satisfactory for the handling, storage, or preparation +of foods, as it is difficult to keep wood in a sanitary condition. +Uncleanliness of dishes in which foods are placed is too often caused by +the use of foul dishcloths and failure to thoroughly wash and rinse the +dishes. It is always well to rinse dishes with scalding water, as colds +and skin diseases may be communicated from the edges of drinking +glasses, and from forks and spoons, and, unless the dish towels are kept +scrupulously clean, it is more sanitary to drain the dishes than to wipe +them. + +286. Contamination from Unclean Dishcloths.--When the dishcloth is +foul, the fat absorbed by the fibers becomes rancid, the proteids +undergo putrefaction changes with formation of ill-smelling gases +containing nitrogen, the carbohydrates ferment and are particularly +attractive to flies, and all the various disease germs collected on the +surface of the dishcloth are, along with the rancid fat and other +putrifying materials, distributed over the surface of the dishes with +which the cloth comes in contact. + +[Illustration: FIG. 69.--CONTAMINATION OF WELL WATER FROM SURFACE DRAINAGE. + +(After Farmers' Bulletin, U. S. Dept. Agr.)] + +287. Refrigeration.--At a low temperature the insoluble or unorganized +ferments become inactive, but the chemical ferments or enzymes are still +capable of carrying on fermentation. Thus it is that a food, when placed +in a refrigerator or in cold storage, continues to undergo chemical +change. An example of such enzymic action is the curing of beef and +cheese in cold storage. A small amount of ventilation is required when +foods are refrigerated, just sufficient to keep up a slight circulation +of air. It seems not to be generally understood that all fermentation +changes do not cease when food is placed in refrigerators, and this +often leads to neglect in their care. Cleanliness is equally as +essential, or more so, in the refrigeration of food as in its handling +in other ways. Too often the refrigerator is neglected, milk and other +food is spilt, filling the cracks, and slow decomposition sets in. A +well-cared-for refrigerator is an important factor in the preservation +of food, but when it is neglected, it becomes a source of contamination. +Unclean vegetables and food receptacles, impure ice and foul air, are +the most common forms of contamination. The chemical changes which +foods undergo during refrigeration are such as result in softening of +the tissues. + +288. Soil.--The soil about dwellings and places where foods are stored +frequently becomes polluted with decaying animal and vegetable matter, +and in such soils disease-producing organisms readily find lodgment. +Poorly drained soils containing an excess of vegetable matter furnish a +medium in which the tapeworm and the germs of typhoid fever, lockjaw, +and various diseases affecting the digestive tract, may propagate. The +wind carries the dust particles from these contaminated places into +unprotected food, where they cause fermentation changes and the disease +germs multiply. In considering the sanitary condition of a locality, the +character of the soil is an important factor. Whenever there is reason +to suspect that a soil is unsanitary, it should be disinfected with lime +or formaldehyde. Soils about dwellings need care and frequent +disinfecting to keep them in a sanitary condition, equally as much as do +the rooms in the dwellings.[99] In the growing of garden vegetables, +frequently large quantities of fertilizers of unsanitary character are +used, and vegetables often retain mechanically on their surfaces +particles of these. To this dirt clinging to the vegetables have been +traced diseases, as typhoid fever and various digestion disorders. + +289. Disposal of Kitchen Refuse.--Refuse, as vegetable parings, bones, +and meat scraps, unless they are used for food for animals or collected +as garbage, should preferably be burned; then there is no danger of +their furnishing propagating media for disease germs. Garbage cans +should be kept clean, and well covered to protect the contents from +flies. Where the refuse cannot be burned, it should be composted. For +this, a well-drained place should be selected, and the refuse should be +kept covered with earth to keep off the flies and absorb the odors that +arise from the fermenting material, and to prevent its being carried +away by the wind. Lime should be sprinkled about the compost heap, and +from time to time it should be drawn away and the place covered with +clean earth. It is very unsanitary to throw all of the kitchen refuse in +the same place year after year without resorting to any means for +keeping the soil in a sanitary condition. Although composting refuse is +not as sanitary as burning, it is far more sanitary than neglecting to +care for it at all, as is too frequently the case. + +Ground polluted with kitchen refuse containing large amounts of fatty +material and soap becomes diseased, so that the natural fermentation +changes fail to take place, and the soil becomes "sewage sick" and gets +in such a condition that vegetation will not grow. Failure to properly +dispose of kitchen refuse is frequently the cause of the spread of germ +diseases, through the dust and flies that are attracted by the material +and carry the germs from the refuse pile to food. + +[Illustration: FIG. 70.--PLUMBING OF SINK. + +1, 1, house side of trap, filled with water; 2, vent pipe; 3, drain pipe +connecting with sewer.] + +Where there is no drainage system, disposal of the liquid refuse is a +serious problem. Drain basins and cesspools are often resorted to, and +these may become additional sources of contamination. As stated in the +chapter on well water, direct communication is frequently established +between such places and shallow wells. Where the only place for the +disposal of waste water is the surface of the ground, it should be +thrown some distance from the house and where it will drain from and not +toward the well. The land should be well drained and open to the +sunlight. Coarse sand and lime should be sprinkled over it frequently, +and occasionally the soil should be removed and replaced with fresh. +Sunlight, aeration, and disinfection of the soil and good drainage are +necessary, in order to keep in a sanitary condition the place where the +dish water is thrown. + +Poor plumbing is often the cause of contaminated food. The gases which +escape from unclean traps may carry with them solid particles of organic +matter in various stages of decay. The "house side" of traps always +ventilates into the rooms, and hence it is important that they be kept +scrupulously clean. Where the drip pipe from the refrigerator drains +directly into the sewerage system, there is always danger. Special +attention should be given to the care of plumbing near places where +foods are stored. Frequently there are leaky joints due to settling of +the dwellings or to extreme changes in temperature, and the plumbing +should be occasionally inspected by one familiar with the subject.[100] + +290. General Considerations.--In order to keep food in the most +wholesome condition, special care should be taken that all of its +surroundings are sanitary. The air, the dishes in which the food is +placed, the refrigerator, cellar or closet where stored, and the other +food with which it comes in contact, all influence the wholesomeness or +cause contamination. A food may contain sufficient nutrients to give it +high value, and yet, on account of products formed during fermentation, +be poisonous. Foods are particularly susceptible to putrefaction +changes, and chemicals and preservatives added as preventives, with a +view of retarding these changes, are objectionable, besides failing to +prevent all fermentation from taking place. Intelligent thought should +be exercised in the care of food, for the health of the consumer is +largely dependent upon the purity and wholesomeness of the food supply. + +[Illustration: FIG. 71.--A PETRI DISH, SHOWING COLONIES OF +BACTERIA PRODUCED BY ALLOWING A HOUSE FLY TO CRAWL OVER SURFACE. + +(From Minnesota Experiment Station Bulletin No. 93.)] + + + + +CHAPTER XXI + +LABORATORY PRACTICE + + +Object of Laboratory Practice, Laboratory Note-book, and Suggestions +for Laboratory Practice.--The aim of the laboratory practice is to give +the students an idea of the composition, uses, and values of food +materials, and the part which chemistry takes in sanitation and +household affairs; also to enable them by simple tests to detect some of +the more common adulterants in foods. + +Before performing an experiment, the student is advised to review those +topics presented in the text which have a bearing upon the experiment, +so that a clear conception may be gained of the relationship between the +laboratory work and that of the class room. The student should endeavor +to cultivate the power of observation and to grasp the principle +involved in the work, rather than do it in a merely mechanical and +perfunctory way. Neatness is one of the essentials for success in +laboratory practice, and too much emphasis cannot be laid upon this +requisite to good work. The student should learn to use his time in the +laboratory profitably and economically. He should obtain a clear idea of +what he is to do, and then do it to the best of his ability. If the +experiment is not a success, repeat it. While the work is in progress it +should be given undivided attention. Care should be exercised to prevent +anything getting into the sinks that will clog the plumbing; soil, +matches, broken glass, and paper should be deposited in the waste jars. + +[Illustration: FIG. 72.--APPARATUS USED IN LABORATORY WORK. + +See page 301 for names.] + +A careful record of the experiments should be kept by each student in a +suitable note-book. It is suggested that those students desiring more +time in writing out the experiments than the laboratory period affords, +take notes as they make the various tests, and then amplify and +rearrange them in the evening study time. The final writing up of the +notes should, however, be done before the next laboratory period. +Careful attention should be given to the spelling, language, and +punctuation, and the note-book should represent the student's individual +work. He who attempts to cheat by copying the results of others, only +cheats himself. In recording the results of an experiment, the student +should state briefly and clearly the following: + + + 1. Number and title of experiment. + 2. How the experiment is performed. + 3. What was observed. + 4. What the experiment proves. + +[Illustration: FIG. 73.--BALANCE AND WEIGHTS.] + + +LIST OF APPARATUS USED IN EXPERIMENTS + + 1 Crucible Tongs + 2 Evaporating Dishes + 1 Casserole + 6 Beakers + 12 Test Tubes + 1 Wooden Stand + 1 Test Tube Stand + 1 Sand Bath + 2 Funnels + 1 Tripod + 1 Stoddart Test Tube Clamp + 1 Test Tube Brush + 1 Burner and Tubing + 2 Stirring Rods + 6 Watch Glasses + 2 Erlenmeyer Flasks + 1 Package Filter Paper + 1 Box Matches + 1 Wire Gauze + 2 Burettes + 1 Porcelain Crucible + 1 Aluminum Dish + +Directions for Weighing.--Place the dish or material to be weighed in +the left-hand pan of the balance. With the forceps lay a weight from the +weight box on the right-hand pan. Do not touch the weights with the +hands. If the weight selected is too heavy, replace it with a lighter +weight. Add weights until the pans are counterpoised; this will be +indicated by the needle swinging nearly as many divisions on one side of +the scale as on the other. The brass weights are the gram weights. The +other weights are fractions of a gm. The 500, 200, 100 mg. (milligram) +weights are recorded as 0.5, 0.2, and 0.1 gm. The 50, 20, and 10 mg. +weights as 0.05, 0.02, and 0.01 gm. If the 10, and 2 gm., and the 200, +the 100, and the 50 mg. weights are used, the resulting weight is 12.35 +gms. No moist substances should ever come in contact with the scale +pans. The weights and forceps should always be replaced in the weight +box. Too much care and neatness cannot be exercised in weighing. + +[Illustration: FIG. 74.] + +[Illustration: FIG. 75.--Pouring Reagent from Bottle.] + +Directions for Measuring.--Reagents are measured in graduated +cylinders (see Fig. 74). When the directions call for the addition of 5 +or 10 cc. of a reagent, unless so directed it is not absolutely +necessary to measure the reagent in a measuring cylinder. A large test +tube holds about 30 cc. of water. Measure out 5 cc. of water and +transfer it to a large test tube. Note its volume. Add approximately 5 +cc. of water directly to the test tube. Measure it. Repeat this +operation until you can judge with a fair degree of accuracy the part of +a test tube filled by 5 cc. In the experiments where a burette is used +for measuring reagents, the burette is first filled with the reagent by +means of a funnel. The tip of the burette is allowed to fill before the +readings are made, which are from the lowest point or meniscus. When +reagents are removed from bottles, the stopper should be held between +the first and second fingers of the right hand (see Fig. 75). Hold the +test tube or receptacle that is to receive the reagent in the left hand. +Pour the liquid slowly until the desired amount is secured. Before +inserting the stopper, touch it to the neck of the bottle to catch the +few drops on the edge, thus preventing their streaking down the sides of +the bottle on to the shelf. Replace the bottle in its proper place. +Every precaution should be taken to prevent contamination of reagents. + +[Illustration: FIG. 76.--MICROSCOPE AND ACCESSORIES. + +1, eye-piece or ocular; 2, objective; 3, stage; 4, cover glass; 5, +slide; 6, mirror.] + +Use of the Microscope.--Special directions in the use of the +microscope will be given by the instructor. The object or material to be +examined is placed on a microscopical slide. Care should be exercised to +secure a representative sample, and to properly distribute the substance +on the slide. If a pulverized material is to be examined, use but little +and spread it in as thin a layer as possible. If a liquid, one or two +drops placed on the slide will suffice. The material on the slide is +covered with a cover glass, before it is placed on the stage of the +microscope. In focusing, do not allow the object glass of the microscope +to come in contact with the cover glass. Focus upward, not downward. +Special care should be exercised in focusing and in handling the +eye-piece and objective. A camel's-hair brush, clean dry chamois skin, +or clean silk only should be used in polishing the lenses. Always put +the microscope back in its case after using. + + +Experiment No. 1 + +Water in Flour + +Carefully weigh a porcelain or aluminum dish. (Porcelain must be used if +the ash is to be determined on the same sample.) Place in it about 2 gm. +of flour; record the weight; then place the dish in the water oven for +at least 6 hours. After drying, weigh again, and from the loss of weight +calculate the per cent of water in the flour. (Weight of flour and dish +before drying minus weight of flour and dish after drying equals weight +of water lost. Weight of water divided by weight of flour taken, +multiplied by 100, equals the per cent of water in the flour.) + +How does the amount of water you obtained compare with the amount given +in the tables of analysis? + + +Experiment No. 2 + +Water in Butter + +Carefully weigh a clean, dry aluminum dish, place in it about 2 gms. of +butter, and weigh again. Record the weights. Place the dish containing +butter in the water oven for 5 or 6 hours and then weigh. The loss in +weight represents the water in the butter. Calculate the per cent of +water. Care must be taken to get a representative sample of the butter +to be tested; preferably small amounts should be taken with the butter +trier from various parts of the package. + + +Experiment No. 3 + +Ash in Flour + +Place the porcelain dish containing flour from the preceding experiment +in a muffle furnace and let it remain until the organic matter is +completely volatilized. Cool, weigh, and determine the per cent of ash. +The flour should be burned at the lowest temperature necessary for +complete combustion. + + +Experiment No. 4 + +Nitric Acid Test for Nitrogenous Organic Matter + +To 3 cc. of egg albumin in a test tube add 2 cc. of HNO_{3} (conc.) and +heat. When cool add NH_{4}OH. The nitric acid chemically reacts upon the +albumin, forming yellow xanthoprotein. What change occurs in the +appearance of the egg albumin when the HNO_{3} is added? Is this a +physical or chemical change? What is the name of the compound formed? +What change occurs on adding NH_{4}OH? + + +Experiment No. 5 + +Acidity of Lemons + +With a pipette measure into a small beaker 2 cc. of lemon juice. Add 25 +cc. of water and a few drops of phenolphthalein indicator. From the +burette run in N/10 KOH solution until a faint pink tinge remains +permanently. Note the number of cubic centimeters of KOH solution +required to neutralize the citric acid in the lemon juice. Calculate the +per cent of citric acid. + +(1 cc. of N/10 KOH solution equals 0.00642 gm. citric acid. 1 cc. of +H_{2}O weighs 1 gm. Because of sugar and other matter in solution 1 cc. +of lemon juice weighs approximately 1.03 gm.) + +1. What is the characteristic acid of lemons? 2. What is the salt formed +when the lemon juice is neutralized by the KOH solution? 3. Describe +briefly the process for determining the acidity of lemon juice. 4. What +per cent of acidity did you obtain? 5. How does this compare with the +acidity of vinegar? + + +Experiment No. 6 + +Influence of Heat on Potato Starch Grains + +With the point of a knife scrape slightly the surface of a raw potato +and place a drop of the starchy juice upon the microscopical slide. +Cover with cover glass and examine under the microscope. + +In the evaporating dish cook a small piece of potato, then place a very +small portion upon the slide, and examine with the microscope. + +Make drawings of the starch grains in raw and in cooked potatoes. + + +Experiment No. 7 + +Influence of Yeast on Starch Grains + +Moisten a small portion of the dough prepared with yeast and with the +stirring rod place a drop of the starchy water upon the slide. Cover +with cover glass and examine under the microscope. + +Repeat, examining a drop of starchy water washed from flour. + +Make drawing of wheat starch grain in flour and in dough prepared with +yeast. + + +Experiment No. 8 + +Mechanical Composition of Potatoes + +Wash one potato. Weigh, then peel, making the peeling as thin as +possible. Weigh the peeled potato and weigh the peeling or refuse. +Calculate the per cent of potato that is edible and the per cent that is +refuse. + + +Experiment No. 9 + +Pectose from Apples + +Reduce a small peeled apple to a pulp. Squeeze the pulp through a clean +cloth into a beaker. Add 10 cc. H_{2}O and heat on a sand bath to +coagulate the albumin. Filter, adding a little hot water if necessary. +To the filtrate add 5 cc. alcohol. The precipitate is the pectose +material. + +1. Is the pectose from the apple soluble? 2. Is it coagulated by heat? +3. Is it soluble in alcohol? + + +Experiment No. 10 + +Lemon Extract + +To 5 cc. of the extract in a test tube add an equal volume of water. A +cloudy appearance indicates the presence of lemon oil. If the solution +remains clear after adding the water, the extract does not contain lemon +oil. + +Why does the extract containing lemon oil become cloudy on adding water? + + +Experiment No. 11 + +Vanilla Extract + +Pour into a test tube 5 cc. of the extract to be tested. Evaporate to +one third. Then add sufficient water to restore the original volume. If +a brown, flocculent precipitate is formed, the sample contains pure +vanilla extract. Resin is present in vanilla beans and is extracted in +the essence. The resin is readily soluble in 50 per cent alcohol. If +the alcohol is removed from the extract, the excess of resin is +precipitated, or if free from alkali, it may be precipitated by diluting +the original solution with twice its volume of water. Test the two +samples and compare. + + (Adapted from Leach, "Food Inspection and Analysis.") + +1. Describe the appearance of each sample after evaporating and adding +water. 2. Which sample contains pure vanilla extract? 3. State the +principle underlying this test. + + +Experiment No. 12 + +Testing Olive Oil for Cotton Seed Oil + +Pour into a test tube 5 cc. of the oil to be tested and 5 cc. of +Halphen's Reagent. Mix thoroughly. Plug the test tube loosely with +cotton, and heat in a bath of boiling saturated brine for 15 minutes. If +cotton seed oil is present, a deep red or orange color is produced. Test +two samples and compare. + +Halphen's Reagent.--Mix equal volumes of amyl alcohol and carbon +disulphid containing about one per cent of sulphur in solution. + + (Adapted from Leach, "Food Inspection and Analysis.") + + +Experiment No. 13 + +Testing for Coal Tar Dyes + +Dilute 20 to 30 cc. of the material to 100 cc.; boil for 10 minutes with +10 cc. of a 10 per cent solution of potassium bisulphate and a piece of +white woolen cloth which has previously been boiled in a 0.1 per cent +solution of NaOH and thoroughly washed in water. Remove the cloth from +the solution, wash in boiling water, and dry between pieces of filter +paper. A bright red indicates coal tar dye. If the coloring matter is +entirely from fruit, the woolen cloth will be either uncolored or will +have a faint pink or brown color which is changed to green or yellow by +ammonia and is not restored by washing. This is the Arata test. + + (Adapted, Winston, Conn. Experiment Station Report.) + +1. Describe Arata's wool test for coal tar dyes. 2. What is the +appearance of the woolen cloth when the coloring matter is entirely from +fruit? 3. What effect has NH_{4}OH upon the color? 4. Why is NaOH used? +5. Why may not cotton cloth be used instead of woolen? 6. What can you +say of the use of coal tar dyes in foods? + + +Experiment No. 14 + +Determining the Per Cent of Skin in Beans + +Place in an evaporating dish 10 gm. of beans, 50 cc. of water, and 1/2 +gm. of baking soda. Boil 10 minutes or until the skins are loosened, +then drain off the water. Add cold water and rub the beans together till +the skins slip off. Collect the skins, place on a watch glass and dry in +the water oven for 1/2 hour. Weigh the dried skins and calculate the per +cent of "skin." + +1. What does the soda do? 2. What effect would hard limewater have upon +the skins? 3. How does removal of skins affect food value of beans and +digestibility? + + +Experiment No. 15 + +Extraction of Fat from Peanuts + +Shell three or four peanuts and with the mortar and pestle break them +into small pieces. Place in a test tube and pour over them about 10 cc. +of ether. Cork the test tube and allow it to stand 30 minutes, shaking +occasionally. Filter on to a watch glass and let stand until the ether +evaporates, and then observe the fat. + +1. What is the appearance of the peanut fat? 2. What is the solvent of +the fat? 3. What becomes of the ether? 4. Why should the peanuts be +broken into small pieces? + + +Experiment No. 16 + +Microscopic Examination of Milk + +Place a drop of milk on a microscopical slide and cover with cover +glass. Examine the milk to detect impurities, as dust, hair, refuse, +etc. Make drawings of any foreign matter present. + + +Experiment No. 17 + +Formaldehyde in Cream or Milk + +To 10 cc. of milk in a casserole add 10 cc. of the acid reagent. Heat +slowly over the flame nearly to boiling, holding the casserole in the +hand and giving it a slight rotary movement while heating. The presence +of formaldehyde is indicated by a violet coloration varying in depth +with the amount present. In the absence of formaldehyde the solution +slowly turns brown. + +Acid Reagent.--Commercial hydrochloric acid (sp. gr. 1.2) containing 2 +cc. per liter of 10 per cent ferric chlorid. + + (Adapted from Leach, "Food Inspection and Analysis.") + +1. How may the presence of formaldehyde in milk be detected? 2. Why in +this test is it necessary to use acid containing ferric chlorid? 3. +Describe the appearance of the two samples of milk after adding the acid +reagent and heating. 4. Which sample showed the presence of +formaldehyde? + + +Experiment No. 18 + +Gelatine in Cream or Milk + +To 20 cc. of milk or cream in a beaker add 20 cc. of acid mercuric +nitrate and about 40 cc. of H_{2}O. Let stand for a few minutes and +filter. Filtrate will be cloudy if gelatine is present. + +Add 1/2 cc. of a dilute solution of picric acid--a heavy yellow +precipitate indicates gelatine. + +Acid Mercuric Nitrate.--1 part by weight of Hg, 2 parts HNO_{3} (sp. +gr. 1.42). Dilute 25 times with water. + + +Experiment No. 19 + +Testing for Oleomargarine + +Apply the following tests to two samples of the material: + +Boiling or Spoon Test.--Melt the sample to be tested--a piece about +the size of a chestnut--in a large spoon, hastening the process by +stirring with a splinter. Then, increasing the heat, bring to as brisk a +boil as possible and stir thoroughly, not neglecting the outer edges. +Oleomargarine and renovated butter boil noisily, sputtering like a +mixture of grease and water, and produce no foam, or but very little. +Genuine butter boils with less noise and produces an abundance of foam. + +Waterhouse Test.--Into a small beaker pour 50 cc. of sweet milk. Heat +nearly to boiling and add from 5 to 10 gms. of butter or oleomargarine. +Stir with a glass rod until fat is melted. Then place the beaker in cold +water and stir the milk until the temperature falls sufficiently for the +fat to congeal. At this point the fat, if oleomargarine, can easily be +collected into one lump by means of the rod; while if butter, it will +granulate and cannot be collected. + + (From Farmers' Bul. 131, U. S. Dept. of Agriculture.) + +1. Name two simple tests for distinguishing butter and oleomargarine. 2. +Describe these tests. 3. Why do butter and oleomargarine respond +differently to these tests? 4. Are these tests based upon chemical or +physical properties of the fats? + + +Experiment No. 20 + +Testing for Watering or Skimming of Milk + +_a._ Fat Content of Milk by Means of Babcock Test.--Measure with +pipette into test bottle 17.6 cc. of milk. Sample should be carefully +taken and well mixed. Measure with cylinder 17.5 cc. commercial +H_{2}SO_{4} and add to milk in test bottle. (See Fig. 25.) Mix acid and +milk by rotating the bottle. Then place test bottles in centrifugal +machine and whirl 5 minutes. Add sufficient hot water to test bottles to +bring contents up to about the 8th mark on stem. Then whirl bottles 2 +minutes longer and read fat. Read from extreme lowest to highest point. +Each large division as 1 to 2 represents a whole per cent, each small +division 0.2 of a per cent. + +_b._ Determining Specific Gravity by Means of Lactometer.--Pour 150 +cc. of milk into 200 cc. cylinder. Place lactometer in milk and note +depth to which it sinks as indicated on stem. Note also temperature of +milk. For each 10 deg. above 60 deg. F. add 1 to the lactometer number, +in order to make the necessary correction for temperature. For example, if +milk has sp. gr. of 1.032 at temperature of 70 deg., it will be equivalent +to sp. gr. of 1.033 at 60 deg. Ordinarily milk has a sp. gr. of 1.029 to +1.034. If milk has sp. gr. less than 1.029, or contains less than 3 per +cent fat, it may be considered watered milk. If the milk has a high sp. +gr. (above 1.035) and a low content of fat, some of the fat has been +removed. + + (For extended direction for milk testing see Snyder's "Dairy Chemistry.") + + +Experiment No. 21 + +Boric Acid in Meat + +Cut into very small pieces 5 gms, of meat, removing all the fat +possible. Place in an evaporating dish with 20 to 25 cc. of water to +which a few drops of HCl have been added and warm slightly. Dip a piece +of turmeric paper in the meat extract and dry. A rose-red color of the +turmeric paper after drying (turned olive by a weak ammonia solution) is +indicative of boric acid. + +1. How may meat be tested for boric acid? 2. Why is HCl added to the +water? 3. Why is the water containing the meat warmed slightly? 4. What +is the appearance of the turmeric paper after being dipped in the meat +extract and dried? 5. What change takes place when it is moistened with +ammonia, and why? + + +Experiment No. 22 + +Microscopic Examination of Cereal Starch Grains + +Make a microscopic examination and drawings of wheat, corn, rice, and +oat starch grains, comparing them with the drawings of the different +starch grains on the chart. If the material is coarse, pulverize in a +mortar and filter through cloth. Place a drop or two of the starchy +water on the slide, cover with a cover glass, and examine. + + +Experiment No. 23 + +Identification of Commercial Cereals + +Examine under the microscope two samples of cereal breakfast foods, and +by comparison with the wheat, corn, and oat starch grains previously +examined tell of what grains the breakfast foods are made and their +approximate food value. + + +Experiment No. 24 + +Granulation and Color of Flour + +Arrange on glass plate, in order of color, samples of all the different +grades of flour. Note the differences in color. How do these differences +correspond with the grades of the flour? Examine the flour with a +microscope, noting any coarse or dark-colored particles of bran or dust. +Rub some of the flour between the thumb and forefinger. Note if any +granular particles can be detected. + + +Experiment No. 25 + +Capacity of Flour to absorb Water + +Weigh out 15 gms. of soft wheat flour into an evaporating dish; then add +from burette a measured quantity of water sufficient to make a stiff +dough. Note the amount of water required for this purpose. Repeat the +operation, using hard wheat flour. + +1. How may the absorptive power of a flour be determined? 2. To what is +it due? 3. Why do some flours absorb more water than others? + + +Experiment No. 26 + +Acidity of Flour + +Weigh into a flask 20 gms. of flour and add 200 cc. distilled water. +Shake vigorously. After letting stand 30 minutes, filter and then +titrate 50 cc. of the filtrate against standard KOH solution, using +phenolphthalein as indicator, 1 cc. of the alkali equals 0.009 gms. +lactic acid. Calculate the per cent of acid present. + +1. How may the acidity of a flour be determined? 2. The acidity is +expressed in percentage amounts of what acid? 3. What per cent of +acidity is found in normal flours? 4. What does a high acidity of a +flour indicate? + + +Experiment No. 27 + +Moist and Dry Gluten + +Weigh 30 gms. of flour into a porcelain dish. Make the flour into a +stiff dough. After 30 minutes obtain the gluten by washing, being +careful to remove all the starch and prevent any losses. Squeeze the +water from the gluten as thoroughly as possible. Weigh the moist gluten +and calculate the per cent. Dry the gluten in the water oven and +calculate the per cent of dry gluten. + + +Experiment No. 28 + +Gliadin from Flour + +Place in a flask 10 gms. of flour, 30 cc. of alcohol, and 20 cc. of +water. Cork the flask and shake, and after a few minutes shake again. +Allow the alcohol to act on the flour for an hour, or until the next +day. Then filter off the alcohol solution and evaporate the filtrate to +dryness over the water bath. Examine the residue; to a portion add a +little water; burn a small portion and observe odor. + +1. Describe the appearance of the gliadin. 2. What was the result when +water was added? 3. When burned, what was the odor of the gliadin, and +what does this indicate? 4. What is gliadin? + + +Experiment No. 29 + +Bread-making Test + +Make a "sponge" by mixing together: + + 12 gm. sugar, + 12 gm. yeast (compressed), + 4 gm. salt, + 175 cc. water (temp. 32 deg. C.). + +Let stand 1/2 hour at a temperature of 30 deg. C. In a large bowl, mix +with a knife or spatula 7.7 gms. of lard with 248.6 gms. of flour. Then +add 160 cc. of the "sponge," or as much as is needed to make a good stiff +dough, and mix thoroughly, using the spatula. With some flours as small +a quantity as 150 cc. of sponge may be used. If more moisture is +necessary, add H_{2}O. Keep at temperature of 30 deg. C. Allow the dough +to stand 50 minutes to first pulling, 40 minutes to second pulling, and +30 to 50 minutes to the pan. Let it rise to top of pan and then bake for +1/2 hour in an oven at a temperature of 180 deg. C. One loaf of bread is +made of patent flour of known quality as a standard for comparison, and +other loaves of the flours to be tested. Compare the loaves as to size +(cubic contents), color, porosity, odor, taste, nature of crust, and +form of loaf. + + +Experiment No. 30 + +Microscopic Examination of Yeast + +On a watch glass mix thoroughly a very small piece of yeast with about +5 cc. of water and then with the stirring rod place a drop of this +solution on the microscopical slide, adding a drop of very dilute methyl +violet solution. Cover with the cover glass and examine under the +microscope. The living active cells appear colorless while the decayed +and lifeless ones are stained. Yeast cells are circular or oval in +shape. (See Fig. 46.) + + (Adapted from Leach, "Food Inspection and Analysis.") + + +Experiment No. 31 + +Testing Baking Powders for Alum + +Place about 2 gms. of flour in a dish with 1/2 gm. baking powder. Add +enough water to make a dough and then 2 or 3 drops of tincture of +logwood and 2 or 3 drops of ammonium carbonate solution. Mix well and +observe; a blue color indicates alum. Try the same test, using flour +only for comparison. + +1. How do you test a baking powder for alum? 2. What difference in color +did you observe in the test with the baking powder containing alum and +in that with the flour only? 3. Why is the (NH_{4})_{2}CO_{3} solution +used? + + +Experiment No. 32 + +Testing Baking Powders for Phosphoric Acid + +Dissolve 1/2 gm. of baking powder in 5 cc. of H_{2}O and 3 cc. HNO_{3}. +Filter and add 3 cc. ammonium molybdate. Heat gently. A yellow +precipitate indicates phosphoric acid. + +1. How do you test a baking powder for phosphoric acid? 2. What is the +yellow precipitate obtained in this test? + + +Experiment No. 33 + +Testing Baking Powders for Ammonia + +Dissolve 1/2 gm. of material in 10 cc. water; filter off any insoluble +residue and to the filtrate add 2 or 3 cc. NaOH and apply heat. Test the +gas given off with moistened turmeric paper. If NH_{3} is present, the +paper will be colored brown. Do not allow the paper to come in contact +with the liquid or sides of the test tube. (Perform the tests on two +samples of baking powder.) + +1. How do you test a baking powder for ammonia? 2. Why do you add NaOH? +3. Why must you be careful not to let the turmeric paper touch the sides +of the test tube or the liquid? + + +Experiment No. 34 + +Vinegar Solids + +Into a weighed aluminum or porcelain dish pour 10 cc. of vinegar. Weigh +and then evaporate over boiling water. To drive off the last traces of +moisture dry in the water oven for an hour. Cool and weigh. Calculate +the per cent of solids. Observe the appearance of the solids. Test both +samples and compare. + +1. How may the per cent of solids in vinegar be determined? 2. Describe +the appearance of the solids from the good and from the poor sample of +vinegar. 3. What is the legal standard for vinegar solids in your state? + + +Experiment No. 35 + +Specific Gravity of Vinegar + +Pour 170 cc. vinegar into 200 cc. cylinder. Place a hydrometer for heavy +liquids (sp. gr. 1 to 1.1) in the cylinder. Note the depth to which it +sinks and the point registered on the scale on the stem. Note +temperature of vinegar. Record specific gravity of vinegar. + +1. What effect would addition of water to vinegar have upon its specific +gravity? 2. What effect would addition of such material as sugar have +upon specific gravity? 3. Why should the specific gravity of vinegar be +fairly constant? 4. What would be the weight of 1000 cc. of vinegar +calculated from the specific gravity? + + +Experiment No. 36 + +Acidity of Vinegar + +Into a small beaker pour 6 cc. of vinegar and 10 cc. of water and a few +drops of phenolphthalein indicator. Run in standard KOH solution from a +burette until a faint pink tinge remains permanently. Note the number of +cubic centimeters of KOH solution required to neutralize the acid. +Divide this number by 10, which will give approximately the per cent of +acetic acid. + +1. How may the per cent of acidity of vinegar be determined? 2. Why was +phenolphthalein used? 3. Why was KOH used? 4. What acids does vinegar +contain? 5. What is the legal requirement in this state for acetic acid +in vinegar? 6. How did the acidity you obtained compare with this legal +requirement? + + +Experiment No. 37 + +Deportment of Vinegar with Reagents + +To 10 cc. of vinegar in a test tube add 8 or 10 drops of lead +sub-acetate and shake. Observe the precipitate. Lead sub-acetate +precipitates mainly the malic acid which is always present in cider +vinegar. + +1. How may the presence of malic acid in a vinegar be detected? 2. +Describe the precipitate. 3. What does malic acid in a vinegar indicate? + + +Experiment No. 38 + +Testing Mustard for Turmeric + +Place 1 gm. of ground mustard on a small watch glass and moisten +slightly with water. Add 2 or 3 drops of NH_{4}OH, stirring well with a +glass rod. A brown color indicates turmeric present in considerable +quantity. + +Test a sample of good mustard and one adulterated with turmeric and +compare the results. + + +Experiment No. 39 + +Examination of Tea Leaves + +Soak a small amount of tea and unroll 8 or 10 of the leaves. Make a +drawing of a tea leaf. Observe the proportion of stems in each of three +samples of tea; also the relative proportion of large and small leaves. +Observe if the leaves are even as to size and of a uniform color. + + +Experiment No. 40 + +Action of Iron Compounds upon Tannic Acid + +Make an infusion of tea by placing 3 gms. of tea in 100 cc. of hot water +and stirring well. Filter off some of the infusion and test 5 cc. with +ferrous sulphate solution made by dissolving 1 gm. FeSO_{4} in 10 cc. +H_{2}O and filtering. Note the result. + +1. What change in color did you observe when the ferrous sulphate +solution was added to the tea infusion? 2. What effect would waters +containing iron have upon the tea infusion? + + +Experiment No. 41 + +Identification of Coffee Berries + +Examine Rio, Java, and Mocha coffee berries. Describe each. Note the +characteristics of each kind of coffee berry. + + +Experiment No. 42 + +Detecting Chicory in Coffee + +Fill a beaker with water and place about a teaspoonful of ground coffee +on the surface. If much of the ground material sinks and it imparts a +dark brown color to the lower portion of the liquid, it is an indication +of the presence of chicory. Pure coffee floats on water. Chicory has a +higher specific gravity than coffee. + +1. How may the presence of chicory in ground coffee be detected? 2. Why +does coffee float on the water while chicory sinks? 3. What effect does +chicory have upon the color of water? + + +Experiment No. 43 + +Testing Hard and Soft Waters + +Partially fill a large cylinder with very hard water. This may be +prepared by dissolving 0.1 to 0.2 gm. calcium chloride in 500 cc. of +ordinary water. Add to this a measured quantity of soap solution. Mix +well and notice how many cubic centimeters of soap solution must be used +before a permanent lather is formed, also notice the precipitate of +"lime soap." Repeat this experiment, using either rain or distilled +water, and compare the cubic centimeters of soap solution used with that +in former test. Repeat the test, using tap water. + +Soap Solution.--Scrape 10 gms. of castile soap into fine shavings and +dissolve in a liter of alcohol, dilute with 1/3 water. Filter if not +clear and keep in a tightly stoppered bottle. + +1. Why is more soap required to form a lather with hard water than with +soft water? 2. What is meant by "lime soap"? Describe its appearance. 3. +How may hard waters be softened for household purposes? + + +Experiment No. 44 + +Solvent Action of Water on Lead + +Put 1 gm. of clean bright lead shavings into a test tube containing 10 +cc. of distilled water. After 24 hours decant the clear liquid into a +second test tube, acidify slightly with HCL, and add a little hydrogen +sulphid water. A black or brownish coloration indicates lead in +solution. + + (Adapted from Caldwell and Breneman, "Introductory Chemical Practice.") + +Under what conditions may lead pipes be objectionable? + + +Experiment No. 45 + +Suspended Matter in Water + +Place a drop of water on the microscopical slide, cover with cover +glass, and examine with the microscope. Note the occurrence and +appearance of any suspended matter in the water. + + +Experiment No. 46 + +Organic Matter in Water + +Pour into the evaporating dish 100 cc. H_{2}O and evaporate to dryness +over the sand bath. Ignite the solids. If the solids blacken when +ignited, the water contains organic matter. + + +Experiment No. 47 + +Deposition of Lime by Boiling Water + +Boil for a few minutes about 200 cc. of water in a flask. After the +water is cool, note any sediment of lime or turbidity of the water due +to expelling the carbon dioxid. + +1. What is meant by a "hard" water? 2. What do the terms "temporary" and +"permanent" hardness of water mean? 3. What acts as a solvent of the +lime in water? 4. Why does boiling cause the lime to be deposited? + + +Experiment No. 48 + +Qualitative Tests for Minerals in Water + +Test for Chlorids.--To 10 cc. of H_{2}O add a few drops of HNO_{3} and +2 cc. of AgNO_{3}. A white precipitate indicates the presence of +chlorids, usually in the form of sodium chlorid. + +Test for Sulphates.--To 10 cc. of water add 2 cc. of dilute HCl and 2 +cc. of BaCl_{2}. A cloudiness or the formation of a white precipitate +indicates the presence of sulphates. + +Test for Iron.--If a brown sediment is formed in water exposed to the +air for some time, it is probably iron hydroxid. To 10 cc. of the water +add a few drops of HNO_{3}, heat, and then add 1/2 cc. of NH_{4}CNS. A +red color indicates the presence of iron. + +Test for CaO and MgO.--To 10 cc. of H_{2}O add 5 cc. NH_{4}OH. If a +precipitate forms, filter it off, and to the filtrate add 3 cc. NH_{4}Cl +and 5 cc. (NH_{4})_{2}C_{2}O_{4}. The precipitate is CaC{2}O_{4}, and +the filtrate contains the magnesia. Filter and add 5 cc. Na_{3}PO_{4} to +precipitate MgNH_{4}PO_{4}. + +1. How would you test a water to detect the presence of organic matter? +2. Name some mineral impurities often found in water. 3. Describe the +test for chlorids; for sulphates; for iron; for lime; for magnesium. 4. +Of the two classes of impurities found in water, which is the more +harmful? 5. Name three ways of purifying waters known to be impure, and +tell which is the most effectual. + + +Experiment No. 49 + +Testing for Nitrites in Water + +To 50 cc. of water in a small beaker add with a pipette 2 cc. of +naphthylamine hydrochloride and then 2 cc. of sulphanilic acid. Stir +well and wait 20 minutes for color to develop. A pink color indicates +nitrites. + + +REAGENTS USED + +Sulphanilic Acid.--Dissolve 5 gm. in 150 cc. of dilute acetic acid; +sp. gr. 1.04. + +Naphthylamine Hydrochloride.--Boil 0.1 gm. of solid [Greek: +a]-amidonaphthaline (naphthylamine) in 20 cc. of water, filter the +solution through a plug of absorbent cotton, and mix the nitrate with +180 cc. of dilute acetic acid. All water used must be free from +nitrites, and all vessels must be rinsed out with such water before +tests are applied. + +1. Would a water showing the presence of nitrites be a safe drinking +water? Why? 2. What are nitrites? 3. What does the presence of nitrites +indicate? 4. Are small amounts of nitrites, when not associated with +bacteria, injurious? + + + + +REVIEW QUESTIONS + + +CHAPTER I + +GENERAL COMPOSITION OF FOODS + +1. To what extent is water present in foods? 2. What foods contain the +most, and what foods the least water? 3. How does the water content of +some foods vary with the hydroscopicity of the air? 4. How may changes +in water content of foods affect their weight? 5. Why is it necessary to +consider the water content of foods in assigning nutritive values? 6. +How is the dry matter of a food determined? 7. Why is the determination +of the water in a food often a difficult process? 8. What is the ash or +mineral matter of a food? 9. How is it obtained? 10. What is its source? +11. Of what is the ash of plants composed? 12. What part in plant life +do these ash elements take? 13. Name the ash elements essential for +plant growth. 14. Which of the mineral elements take the most essential +part in animal nutrition? 15. In what form are these elements usually +considered most valuable? 16. Why is sodium chloride or common salt +necessary for animal life? 17. How do food materials differ in ash +content? 18. Define organic matter of foods. 19. How is it obtained? 20. +Of what is it composed? 21. Into what is the organic matter converted +when it is burned? 22. Give the two large classes of organic compounds +found in food materials. 23. Name the various subdivisions of the +non-nitrogenous compounds. 24. What are the carbohydrates? 25. Give +their general composition. 26. What is cellulose? 27. Where is it found? +28. What is its function in plants? 29. What is its food value? 30. In +what way may cellulose be of value in a ration? 31. In what way may it +impart a negative value to a ration? 32. What is starch? 33. Where is +it mainly found in plants? 34. Give the mechanical structure of the +starch grain. 35. Why is starch insoluble in cold water? 36. How do +starch grains from different sources differ in structure? 37. What +effect does heat have upon starch? 38. Define hydration of starch. 39. +Under what conditions does this change take place? 40. What value as a +nutrient does starch possess? 41. What is sugar? 42. How does it +resemble and how differ in composition from starch? 43. What are the +pectose substances? 44. How are they affected by heat? 45. What food +value do they possess? 46. What is nitrogen-free-extract? 47. How is it +obtained? 48. How may the nitrogen-free-extract of one food differ from +that of another? 49. What are the fats? 50. How do they differ in +composition from the starches? 51. Why does fat when burned or digested +produce more heat than starch or sugar? 52. Name the separate fats of +which animal and vegetable foods are composed. 53. Give some of the +physical characteristics of fat. 54. What is the iodine absorption +number of a fat? 55. How does the specific gravity of fat compare with +that of water? 56. Into what two constituents may all fats be separated? +57. What is ether extract? 58. How does the ether extract in fats vary +in composition and nutritive value? 59. What are the organic acids? 60. +Name those most commonly met with in foods. 61. What nutritive value do +they possess? 62. What dietetic value? 63. What value are they to the +growing plant? 64. What organic acids are found in animal foods? 65. +What are the essential oils? 66. How do they differ from the fixed oils, +or fats? 67. What property do the essential oils impart to foods? 68. +What food value do they possess? 69. What dietetic value? 70. What are +the mixed compounds? 71. How may a compound impart a negative value to a +food? 72. What is the nutritive value of the non-nitrogenous compounds, +taken as a class? 73. Why is it necessary that nitrogenous and +non-nitrogenous compounds be blended in a ration? 74. What are the +nitrogenous compounds? 75. How do they differ from the non-nitrogenous +compounds? 76. Name the four subdivisions of the nitrogenous compounds. +77. What is protein? 78. What is characteristic as to its nitrogen +content? 79. What are some of the derivative products that can be +obtained from the protein molecule? 80. How does the protein content of +animal bodies compare with that of plants? 81. Name the various +subdivisions of the proteins. 82. What is albumin, and how may it be +obtained from a food? 83. What is globulin, and how is it obtained from +a food? 84. Give some examples of globulins. 85. What are the +albuminates, and how are they affected by the action of acids and +alkalies? 86. What are the peptones, and how do they differ from the +albumins? 87. How are the peptones produced from other proteids? 88. +What are the insoluble proteids? 89. Give an example. 90. Which of the +proteids are found to the greatest extent in foods? 91. Why may proteids +from different sources vary in their nutritive value? 92. What general +change do the proteids undergo during digestion? 93. What is crude +protein? 94. How is the crude protein content of a food calculated? 95. +Why is the nitrogen content of a food more absolute than the crude +protein content? 96. What food value do the proteins possess? 97. Why +may proteins serve so many functions in the body? 98. Why is protein +necessary as a nutrient? 99. What is the effect of an excess of protein +in the ration? 100. What is the effect of a scant amount of protein in a +ration? 101. What are the albuminoids? 102. Name borne materials that +contain large amounts of albuminoids. 103. What food value do the +albuminoids possess? 104. What are the amids? 105. How are they formed +in plants? 106. What is their source in animals? 107. What general +changes does the element nitrogen undergo in plant and animal bodies? +108. What is the food value of the amids? 109. What are the alkaloids? +110. What is their food value? 111. What effect do some alkaloids exert +upon the animal body? 112. How may they be produced in animal foods? +113. What general relationship exists between the various nitrogenous +compounds? 114. Why is it essential that the animal body be supplied +with nitrogenous food in the form of proteids? 115. Name the cycle of +changes through which the element nitrogen passes in plant and animal +bodies. + + +CHAPTER II + +CHANGES IN COMPOSITION OF FOODS DURING COOKING AND PREPARATION + +116. How do raw and cooked foods compare in general composition? 117. In +what ways are foods acted upon during cooking? 118. What causes chemical +changes to take place during cooking? 119. What are the principal +compounds that are changed during the process of cooking? 120. How does +cooking affect the cellulose of foods? 121. What change does starch +undergo during cooking? 122. When foods containing starch are baked, +what change occurs? 123. How are the sugars acted upon when foods are +cooked? 124. What effect does dry heat have upon sugar? 125. What change +occurs to the fats during cooking? 126. How does this affect nutritive +value? 127. What changes do the proteids undergo during cooking? 128. +Why does the action of heat affect various proteids in different ways? +129. Why are chemical changes, as hydration, often desirable in the +cooking and preparation of foods? 130. What physical changes do +vegetable and animal tissues undergo when cooked? 131. How do foods +change in weight during cooking? 132. Why is a prolonged high +temperature unnecessary to secure the best results in cooking? 133. To +what extent is the energy of fuels utilized for producing mechanical and +chemical changes in foods during cooking? 134. What effect does cooking +have upon the bacterial flora of foods? 135. In what ways do bacteria +exert a favorable influence in the preparation of foods? 136. How may +certain classes of bacteria exert unfavorable changes in the preparation +of foods? 137. What are the insoluble ferments? 138. What are the +soluble ferments? 139. What part do they take in animal and plant +nutrition? 140. Define aerobic ferments. 141. Define anaerobic ferments. +142. What general relationship exists between the chemical, physical, +and bacteriological changes that take place in foods? 143. Why should +foods also possess an esthetic value? 144. What kinds of colors should +be used in the preparation of foods? 145. What processes should be used +for removal of coloring materials from foods? + + +CHAPTER III + +VEGETABLE FOODS + +146. Give the general composition of vegetable foods as a class. 147. +How do vegetable foods differ from animal foods? 148. Name some +vegetables which contain the maximum, and some which contain the minimum +percentage of protein. 149. Give the general composition of potatoes. +150. Of what is the dry matter mainly composed? 151. How much of the +crude protein of potatoes is true protein? 152. What ratio exists +between the nitrogenous and non-nitrogenous compounds in the potato? +153. Give the chemical composition of the potato. 154. What influence do +different methods of boiling have upon the crude protein content of +potatoes? 155. To what extent are the nutrients of potatoes digested and +absorbed by the body? 156. What value do potatoes impart to the ration? +157. How do sweet potatoes differ in chemical composition and food value +from white potatoes? 158. How do carrots differ in composition from +potatoes? 159. What is characteristic of the dry matter of the carrot? +160. How do carrots and milk differ in composition? 161. To what is the +color of the carrot due? 162. To what extent are the nutrients removed +in the cooking of carrots? 163. What is the value of carrots in a +ration? 164. Give the characteristics of the composition of parsnips. +165. How does the starch of parsnips differ from that of potatoes? 166. +How does the mineral matter of parsnips differ from that of potatoes? +167. How does the cabbage differ in general composition from many +vegetables? 168. To what extent are nutrients extracted in the boiling +of cabbage? 169. Give the nutritive value of cabbage. 170. How does the +cauliflower differ from cabbage? 171. Give the general composition of +beets. 172. Give the general composition of cucumbers. 173. What +nutritive value has lettuce? 174. Give the composition and dietetic +value of onions. 175. How does the ratio of nitrogenous and +non-nitrogenous compounds in spinach differ from that in many other +vegetables? 176. Give the general composition and nutritive value of +asparagus. 177. How much nutritive material do melons contain? 178. What +are the principal compounds of tomatoes? 179. What nutrients do they +supply to the ration? 180. In the canning of tomatoes, why is it +desirable to conserve the juices? 181. How does sweet corn differ in +composition from fully matured corn? 182. What nutritive value does the +egg plant possess? 183. What are the principal nutrients of squash? 184. +What nutritive material does celery contain? 185. To what does celery +owe its dietetic value? 186. Why are vegetables necessary in a ration? +187. Why is it not possible to value many vegetable foods simply on the +basis of percentage of nutrients present? 188. Name the miscellaneous +compounds which many vegetables contain, and the characteristics which +these may impart. 189. Why is it necessary to consider the sanitary +conditions of vegetables? 190. How do canned vegetables differ in +composition and food value from fresh vegetables? 191. What proportion +of vegetables is refuse and non-edible parts? 192. Why is it necessary +to consider the refuse of a food in determining its nutritive value? + + +CHAPTER IV + +FRUITS + +193. To what extent do fruits contain water and dry matter? 194. Give +the general composition of fruits. 195. What compounds impart taste and +flavor? 196. How much nutrients do fruits add to a ration? 197. Why is +it not right to determine the value of fruits entirely on the basis of +nutrients? 198. Give the general composition of apples? 199. What +compound is present to the greatest extent in the dry matter of apples? +200. How do apples differ in composition? 201. Give the general physical +composition of oranges. 202. What nutrients are present to the greatest +extent in oranges? 203. How do lemons differ in composition from +oranges? 204. How does grape fruit resemble and how differ in chemical +composition from oranges and lemons? 205. What are the main compounds in +strawberries? 206. In what ways are strawberries valuable in a ration? +207. Of what is grape juice mainly composed? 208. What acid is in +grapes, and what is its commercial value? 209. To what are the +differences in flavor and taste due? 210. How do ripe olives differ in +composition from green olives? 211. What is the food value of the olive? +212. What physiological property does olive oil have? 213. What is the +principal nutrient in peaches? 214. What compounds give flavor to +peaches? 215. Of what does the dry matter of plums mainly consist? 216. +How do plums differ in composition from many other fruits? 217. What are +prunes? What is their food value? 218. How do dried fruits differ in +composition from fresh fruits? 219. What should be the stage of ripeness +of fruit in order to secure the best results in canning? 220. How do +canned fruits differ in composition and nutritive value from fresh +fruits? 221. To what extent are metals dissolved by fruit juices? 222. +Why should tin in which canned goods are preserved be of good quality? +223. What preservatives are sometimes used in the preparation of canned +fruits? 224. What is the objection to their use? 225. Why are fruits +necessary in the ration? 226. What change does heat bring about in the +pectose substances of fruits? + + +CHAPTER V + +SUGAR, MOLASSES, SIRUPS, HONEY, AND CONFECTIONS + +227. What is sugar? 228. From what sources are sugars obtained? 229. +Name the two divisions into which sugars are divided. 230. How are +sugars graded commercially? 231. What per cent of purity has granulated +sugar? 232. How is the coloring material of sugar removed? 233. How is +sugar treated to make it whiter? 234. What value as a nutrient does +sugar possess? 235. Why should sugar be combined with other nutrients? +236. What foods contain appreciable amounts of sugar? 237. Why is an +excessive amount of sugar in a ration undesirable? 238. Does sugar +possess more than condimental value? 239. What is the average quantity +of sugar consumed in this country? 240. What is maple sugar? 241. How +does it differ in composition from other sugar? 242. How is adulterated +maple sugar detected? 243. To what extent is granulated sugar +adulterated? 244. Why is it not easily adulterated? 245. What are the +dextrose sugars? 246. How do they differ chemically from sucrose? 247. +What is the inversion of sugar? 248. In what way does acid act upon +sugar? 249. How are the acid products removed? 250. What is the food +value of glucose? 251. What is molasses? 252. How is it obtained? 253. +Of what is it composed? 254. What gives taste and flavor to molasses? +255. How may molasses act upon metalware? 256. What is the food value of +molasses? 257. What is sirup? 258. Name three kinds of sirup, and +mention materials from which they are prepared. 259. What is the +polariscope, and how is it employed in sugar work? 260. What is honey? +261. How does it differ in composition from sugar? 262. How is strained +honey adulterated? 263. What materials are used in the preparation of +confections? 264. What changes take place in their manufacture? 265. +What materials are used for imparting color? 266. What can you say in +regard to the coal tar colors? 267. What should be the position of candy +in the dietary? 268. What can you say of the comparative value of cane +and beet sugar? 269. How do the commercial grades of sugar compare as to +nutritive value? 270. What are some of the impurities in candy? 271. +What is saccharine? 272. What are its properties? + + +CHAPTER VI + +LEGUMES AND NUTS + +273. What nutrients do the legumes contain in comparatively large +amounts? 274. How does the amount of this nutrient compare with that +found in meats? 275. Why are legumes valuable crops in general farming +and for the feeding of farm animals? 276. Give the general composition +of beans. 277. How do beans compare in protein content with cereals? +278. How does the protein of beans differ from that of many other food +materials? 279. To what extent are the nutrients of beans digested? 280. +What influence does the combination of beans with other foods have upon +digestibility? 281. What influence does removal of skins have upon +digestibility? 282. In what part of the digestive tract are beans mainly +digested? 283. How does the cost of the nutrients in beans compare with +that of the nutrients in other foods? 284. How do string beans differ +from green beans? 285. Give the general composition, digestibility, and +nutritive value of peas. 286. What can you say of the use of copper +sulphate in the preparation of canned peas? 287. What nutrients do +peanuts contain in large amounts? 288. Give the general composition of +nuts. 289. What are the characteristics of pistachio? 290. Give the +general composition of the cocoanut. 291. What is cocoanut butter? 292. +To what extent may nuts contribute to the nutritive value of a ration? + + +CHAPTER VII + +MILK AND DAIRY PRODUCTS + +293. What can you say as to the importance of dairy products in the +dietary? 294. Give the general composition of milk. 295. What compound +in milk is most variable? 296. To what extent are the nutrients in milk +digestible? 297. What influence does milk have upon the digestibility of +other foods? 298. Why is cheese cured in cold storage? 299. How can the +tendency of a milk diet to produce costiveness be overcome? 300. Why is +it necessary to consider the sanitary condition of milk? 301. What +factors influence the sanitary condition of milk? 302. What is certified +milk? 303. What is pasteurized milk? 304. How can milk be pasteurized +for family use? 305. What is tyrotoxicon? 306. What is its source in +milk? 307. To what is the color of milk due? 308. To what extent is +color associated with fat content? 309. What causes souring of milk? +310. What change occurs in the milk sugar? 311. What are the most +favorable conditions for the souring of milk? 312. What are some of the +preservatives used in milk. 313. What objection is urged against their +use? 314. What is condensed milk? 315. What is buttermilk, and what +dietetic value has it? 316. How does goats' milk differ from cows' milk? +317. What is koumiss, and how is it prepared? 318. What are the prepared +milks? 319. How does human milk differ in composition from cows' milk? +320. Give the nutritive value of skim milk. 321. What content of fat +should cream contain? 322. In what ways is milk adulterated? 323. How +are these adulterations detected? 324. Give the general composition of +butter. 325. What is the maximum amount of water that a butter may +contain without being considered adulterated? 326. What can you say in +regard to the digestibility of butter? 327. How is butter adulterated? +328. How does oleomargarine compare in digestibility and food value with +butter? 329. What is the food value of butter? 330. How does cheese +differ in composition from butter? 331. Give the general composition of +cheese. 332. To what are the flavor and odor of cheese due? 333. Why is +cheese ripened? 334. What chemical changes take place during ripening? +335. To what extent are the nutrients of cheese digested? 336. Why is +cheese sometimes considered indigestible? 337. To what extent do the +nutrients of different kinds of cheese vary in digestibility? 338. How +does cheese compare in nutritive value and cost with meats? 339. What is +cottage cheese? 340. What is Roquefort cheese? 341. Name four kinds of +cheese, and say to what each owes its individuality. 342. How is cheese +adulterated? 343. Why are dairy products in older agricultural regions +generally cheaper than meats? + + +CHAPTER VIII + +MEATS AND ANIMAL FOOD PRODUCTS + +344. Give the general composition of meats. 345. How do meats differ in +chemical composition from vegetable foods? 346. What is the principal +non-nitrogenous compound of meats, and what of vegetables? 347. Name the +different classes of proteins in meats. 348. Which class is present in +largest amounts? 349. To what extent are amid compounds present in +meats? 350. What characteristics do amids impart to meats? 351. How are +alkaloids produced in meats? 352. In what ways does the lean meat of +different kinds of animals vary chemically and physically? 353. Give the +general composition of beef. 354. What relationship exists between the +fat and water content of beef? 355. How much refuse have meats? 356. In +what forms are the ash elements (mineral matter) present in meats? 357. +How does veal differ in composition from beef? 358. What general changes +in composition occur as animals mature? 359. How do these compare with +the changes that take place when plants ripen and seeds are produced? +360. How does mutton vary in composition from beef? 361. How does it +compare in food value with beef? 362. How do lamb and mutton differ in +composition? 363. To what extent do the various cuts differ in +composition? 364. How do the more expensive cuts of lamb compare in +nutritive value with the less expensive cuts? 365. How does pork differ +in composition from other meats? 366. Give the general composition of +ham. 367. Give the composition and nutritive value of bacon. 368. How +does bacon compare in food value with other meats? 369. How does the +character of the fat influence the composition and taste of the meat? +370. What influences the texture or toughness of meats? 371. How do +cooked meats compare in composition with raw meats? 372. To what extent +are nutrients lost in the boiling of meats? 373. What influence does the +temperature of the water in which the meat is placed for cooking have +upon the amount of nutrients extracted? 374. To what is the shrinking of +meats in cooking due? 375. Of what does meat extract mainly consist? +376. To what do beef extracts owe their flavor? 377. What is their food +value? 378. What is their dietetic value? 379. What is lard? 380. How +does it differ in composition from other fats? 381. What is imparted to +meats during the smoking process? 382. Why is saltpeter used in the +preservation of meats? 383. Do vegetable foods contain nitrates and +nitrites? 384. How does poultry resemble and how differ in composition +from other meat? 385. Give the characteristics of sound poultry. 386. +Give the general composition of fish. 387. How does the flesh of +different kinds of fish vary in composition? 388. What influence does +salting and preservation have upon composition? 389. How do fish and +meat compare in digestibility? 390. How does the mineral matter and +phosphate content of fish compare with that of other foods? 391. What +are the main nutrients in oysters? 392. Give the general food value of +oysters. 393. What is meant by the fattening of oysters? 394. What +effect does the character of the water used in fattening have upon the +sanitary value? 395. Give the general composition of the egg. 396. How +do different parts of the egg differ in composition? 397. How does the +egg differ in composition from the potato? 398. Is color an index to the +composition of the egg? 399. What effect does cooking have upon the +composition of the egg? 400. What factors influence the flavor of eggs? +401. How do different ways of cooking affect the digestibility? 402. +Under what conditions can eggs be used economically in the dietary? 403. +Why should eggs be purchased and sold by weight? 404. How do canned +meats differ in composition from fresh meats? 405. How do the nutrients +of canned meats compare in cost with those of fresh meat? 406. What are +the advantages of canned meats over fresh meats? 407. What are some of +the materials used in the preservation of meats? + + +CHAPTER IX + +CEREALS + +408. How are the cereals milled? 409. What are the cereals most commonly +used for food purposes? 410. Give the general composition of cereals as +a class. 411. What are the main nutrients in corn preparations? 412. +What influence does the more complete removal of the bran and germ of +corn have upon its digestibility? 413. How does the cost of nutrients in +corn compare with other foods? 414. Why is corn alone not suitable for +bread-making purposes? 415. Why should corn be combined in a ration with +foods mediumly rich in protein? 416. What change takes place in corn +meal from long storage? 417. Give the characteristics and composition of +oat preparations. 418. How does removal of the oat hull affect the +composition of the product? 419. To what extent do the various oat +preparations on the market differ in composition and food value? 420. Do +oats contain any special alkaloidal or stimulating principle? 421. Why +should oatmeal receive longer and more-thorough cooking than many other +foods? 422. To what extent are the nutrients in oatmeal digested? 423. +How do wheat preparations differ in general composition from corn and +oat preparations? 424. What influence upon the composition of the wheat +breakfast foods has partial or complete removal of the bran? 425. What +is the effect upon their digestibility and nutritive value? 426. What +are the special diabetic flours, and how are they prepared? 427. What +are the wheat middlings breakfast foods, and how do they compare in +digestibility and food value with bread? 428. How do they differ +mechanically? 429. How does barley differ from wheat in general +composition? 430. What is barley water, and what nutritive material does +it contain? 431. What cereal does rice resemble in composition? 432. +With what food materials should rice be combined to make a balanced +ration? 433. What can you say as to comparative ease and completeness +of digestibility of rice? 434. Why are cereals valuable in the ration? +435. In what way do they take a mechanical part in digestion? 436. What +are predigested breakfast foods? 437. How would you determine the +general nutritive value of a breakfast food, knowing the kind of cereal +from which it was prepared? 438. To what extent are cereals modified or +changed in composition by cooking? 439. To what extent are the nutrients +of cereal foods digested and absorbed by the body? 440. To what extent +do the cereals supply the body with mineral matter? 441. How does the +phosphate content of cereals compare with that of meats and milk? + + +CHAPTER X + +WHEAT FLOUR + +442. Why is wheat flour especially adapted to bread-making purposes? +443. To what extent may wheat vary in protein content? 444. What are +spring wheats? 445. What are winter wheats? 446. Give the general +characteristics of each. 447. What are glutinous wheats? 448. What are +starchy wheats? 449. Name the different proteids in wheat flour. 450. +About how much starch does wheat flour contain? 451. What other +carbohydrates are also present? 452. What is the roller process of flour +milling? 453. What is meant by the first break? 454. How are the +different products of the wheat kernel separated? 455. What is meant by +middlings flour? 456. What is break flour? 457. What is patent flour? +458. Name the high grade flours. 459. Name the low grade flours. 460. +How are the impurities removed from wheat flour? 461. What per cent of +the wheat kernel is returned as flour? As offals? 462. What becomes of +the wheat germ during milling? 463. What sized bolting cloths are used +in milling? 464. What is graham flour? 465. How does it differ in +mechanical and chemical composition from white flour? 466. What is +entire wheat flour? 467. How does it differ in physical and chemical +composition from white flour? 468. What effect has the refining of +flour upon the ash content? 469. How do low and high grade flours differ +in chemical composition? 470. How do the wheat offals differ in +composition from the flour? 471. What are the factors which influence +the composition of flours? 472. What effect does storage have upon the +bread-making value of flour? 473. What change takes place when new wheat +is stored in an elevator? 474. What is durum wheat flour, and how does +it differ from other flour? 475. What gives flour its color? 476. Why is +color an index of grade? 477. How is the color of a flour determined? +478. How do flours differ in granulation? 479. How does the granulation +affect the physical properties of flour? 480. How is the granulation of +flour approximately determined? 481. How is the absorptive capacity of a +flour determined? 482. What factors cause a variation in the capacity of +flours to absorb water? 483. Give the characteristics of a good gluten. +484. What causes unsound flours? 485. How is the bread-making value of a +flour determined? 486. How are flours bleached? 487. How does bleaching +affect the chemical composition of flour? 488. What influence does +bleaching have upon bread-making value? 489. Traces of what compounds +are formed during bleaching? 490. Are these compounds injurious to +health? 491. What effect does bleaching have upon the color of fiber and +debris particles in flour? 492. Is it possible to bleach low grade +flours and cause them to resemble high grade flours? 493. Are flours +usually adulterated? 494. Why? 495. How would mineral adulterants be +detected? 496. How would the presence of other cereals be detected? 497. +How does flour compare in nutritive value with other foods? 498. How +does the cost of flour compare with that of other foods? 499. What +causes flours to vary so in bread-making value? 500. Why may flours +produced from the same type of wheat vary slightly in character from +year to year? 501. What relationship exists between the nutritive and +bread-making value of a flour? + + +CHAPTER XI + +BREAD AND BREAD MAKING + +502. Define leavened and unleavened bread. 503. Why is yeast used in +bread making? 504. Give the characteristics of a good loaf of bread. +505. Why is flour used for bread making purposes? 506. Name the eight +chemical changes that take place during bread making. 507. To what +extent do losses in dry matter occur during bread making? 508. What +compounds suffer losses during bread making? 509. What is yeast? 510. +What chemical changes does it produce? 511. What becomes of these +products during bread making? 512. How is compressed yeast made? 513. +What part does the alcohol take in bread making? 514. What temperature +is reached in the interior of the loaf during bread making? 515. Through +what chemical changes does starch pass during bread making? 516. To what +extent are soluble carbohydrates formed? 517. In what way is starch +acted upon mechanically? 518. Explain the structure of the starch grains +in flour and in dough after they have been acted upon by the yeast +ferments. 519. To what extent are acids produced in bread making? 520. +What becomes of the acids formed? 521. How may the acids thus developed +affect the properties of other chemical compounds? 522. To what extent +are volatile carbon compounds, other than carbon dioxid and alcohol, +liberated during bread making? 523. What changes occur to the various +proteids during the process of bread making? 524. Why do flours vary in +quality of gluten? 525. To what extent do losses of nitrogen occur +during bread making? 526. How much of the total nitrogen of flour is +present as proteids? 527. How is the fat of flour affected during the +process of bread making? 528. What effect does the addition of 10 per +cent of wheat starch to flour have upon the size of the loaf? 529. What +effect does the addition of 10 per cent of wheat gluten to flour have +upon the size of the loaf? 530. What relationship exists between gluten +content and capacity of a flour to absorb water? 531. Give the general +composition of bread. 532. What factors influence its composition? 533. +What effect does the use of skim milk and lard in bread making have upon +composition? 534. How does the temperature of the flour influence the +bread-making process? 535. Why is it necessary to vary the process of +bread making in order to get the best results with different kinds of +flour? 536. To what extent are the nutrients of bread digested? 537. How +does graham bread compare in digestibility with white bread? 538. How do +graham and entire wheat breads compare in nutritive value with white +bread? 539. What value do graham and entire wheat breads have in the +dietary? 540. Why is white bread generally preferable in the dietary of +the laboring man? 541. How do graham and entire wheat flours compare in +chemical composition with white flour? 542. How do they compare in +mechanical composition? 543. To what is the difference in digestibility +supposed to be due? 544. Are graham and entire wheat breads necessary in +a ration as a source of mineral elements? 545. What is the main +difference in composition between old and new bread? 546. How do +different kinds of bread made from the same flour compare in composition +and nutritive value? 447. How does toast differ in composition from +bread? 548. What influence does toasting have upon digestibility? 549. +What is gained by toasting bread? 550. How does bread compare in +nutritive value with other cereal foods? 551. How does bread compare in +nutritive value with animal foods? + + +CHAPTER XII + +BAKING POWDERS + +552. What is a baking powder? 553. What are the two kinds of materials +which baking powders contain? 554. Name the different types of baking +powders. 555. How does baking powder differ in its action from yeast? +556. What are the cream of tartar baking powders? 557. What is the +nature of the residue which they leave? 558. What are the phosphate +baking powders? 559. What is the nature of the residue which they +leave? 560. Why is the mineral phosphate not considered equally valuable +with that naturally present in foods? 561. What are the alum baking +powders? 562. What residue is left from the alum powders? 563. Which of +the three classes of baking powders is considered the least +objectionable? 564. Why is a new baking powder preferable to one that +has been kept a long time? 565. Why should baking powders be kept in tin +cans, and not in paper? 566. Why are fillers used in the manufacture of +baking powders? 567. How may a baking powder be prepared at home? 568. +How does such a baking powder compare in cost and efficiency with those +purchased in the market? + + +CHAPTER XIII + +VINEGARS, SPICES, AND CONDIMENTS + +569. What is vinegar? 570. How is it made? 571. Give the three chemical +changes that take place in its preparation. 572. Why is air necessary in +the last stage of the process? 573. What ferments take part in the +production of vinegar? 574. What is malt vinegar? 575. What materials +other than apples can be used in the preparation of vinegar? 576. Give +the characteristics of a good vinegar. 577. In what ways are vinegars +adulterated? 578. What food value has vinegar? 579. Why should vinegars +not be stored in metalware? 580. What dietetic value has vinegar? 581. +To what materials do the spices owe their value? 582. What is pepper? +583. What is the difference between white and black pepper? 584. What +compounds give pepper its characteristics? 585. How are peppers +adulterated? 586. What is mustard? 587. Give its general composition. +588. How is it adulterated? 589. What is ginger? 590. How is it prepared +for the market? 591. Give its general composition. 592. What is +cinnamon? 593. What is cassia? 594. What gives these their taste and +flavor? 595. What are cloves? 596. How are they prepared? 597. What is +mace? 598. What is nutmeg? 599. Do the spices have any food value? 600. +What is their dietetic value? 601. Why is excessive use of some of the +spices objectionable? + + +CHAPTER XIV + +TEA, COFFEE, CHOCOLATE, AND COCOA + +602. What is tea? Name the two plants from which it is obtained, the +countries where each grows best, and the number of flushes each yields. +603. Upon what does the quality and grade of tea depend? 604. Give +differences in the preparation and composition of green and black teas. +605. The characteristic flavor of tea is imparted by what compound? 606. +To what compound are its peculiar physiological properties due? 607. +What can you say of the protein in tea as to amount and food value? 608. +Why should tea--especially green tea--be infused for a very short time, +never boiled? 609. What effect has tannin upon the digestion of +proteids? 610. What three points are considered in judging a tea? 611. +What is the most common form of tea adulteration? 612. Describe the +coffee plant and fruit, and its method of preparation for market. 613. +What is the difference in the chemical composition of tea and coffee? +614. Name the characteristic alkaloid of coffee. How does it compare +with theme? 615. Why may coffee not be considered a food? 616. Tell +different ways in which coffee may be adulterated. 617. Which is more +commonly practiced, tea or coffee adulteration? Why? 618. How may real +coffee be distinguished from chicory? Why? 619. Name the three kinds of +coffee in general use. Give distinguishing features of each. Which is +usually considered best? 620. From what are cocoa and chocolate +obtained? 621. Give the two methods of preparing cocoa. 622. What +alkaloid similar to the theme and caffeine of tea and coffee is present +in cocoa and chocolate? 623. What is the difference in preparation of +cocoa and chocolate? 624. What are cereal coffee-substitutes? 625. What +nutritive value have they? 626. How do they differ in composition from +coffee? 627. To what extent does cocoa add to the nutritive value of a +ration? 628. What is plain chocolate? 629. Why do chocolate preparations +vary so widely in composition? 630. What treatment is given to the cocoa +bean in its preparation for commerce? 631. What treatment is sometimes +given to prevent separation of the cocoa fat? 632. In what ways may +cocoa and chocolate preparations be adulterated? + + +CHAPTER XV + +DIGESTIBILITY OF FOODS + +633. Define the term nutrient. 634. Do all the nutrients of food have +the same degree of digestibility? 635. What is a digestion coefficient? +636. How is the digestibility of a food determined? 637. What volatile +products are formed during the digestion of food? 638. Define digestible +protein; digestible carbohydrates, digestible fat. 639. What is the +available energy of a ration? 640. How is it determined? 641. How do the +nutrients, protein, fat, and carbohydrates, compare as to available +energy? 642. Why is it necessary to consider the caloric value of a +ration? 643. Is the protein molecule as completely oxidized in the body +as starch or fat? 644. What residue is left from the digestion of +protein? 645. What part do the soluble ferments take in digestion? 646. +To what extent are the nutrients of animal foods digested? 647. Which +nutrient, protein or fat, is the most completely digested? 648. How do +vegetable foods compare in digestibility with animal foods? 649. What +effect does cellulose have upon digestibility? 650. Which of the +nutrients of vegetables, protein or carbohydrates, is more completely +digested? 651. What mechanical value may cellulose have in a ration? +652. Why must bulk be considered in a ration, as well as nutrient +content? 653. Name the eight most important factors influencing the +digestibility of foods. 654. To what extent does the combination of +foods affect the digestibility of the nutrients? 655. Why does a mixed +ration give better results than when only a single food is used? 656. +How does the amount consumed affect the completeness of the digestive +process? 657. To what extent does the method of preparing food affect +digestibility? 658. What is gained, so far as digestibility is +concerned, by the cooking of foods? 659. To what extent does the +mechanical condition of food affect its digestibility? 660. Why is it +desirable to have some coarsely granulated foods in a ration? 661. Why +should the ration not be composed exclusively of finely granulated +foods? 662. Why is some coarsely granulated food more essential in the +dietary of the sedentary than in the dietary of the laborer? 663. How +does palatability affect the digestive process? 664. Do psychological +processes in any way affect digestion? 665. What physiological +properties do some foods possess? 666. To what are these physiological +properties due? 667. To what extent is individuality a factor in +digestion? 668. To what extent does digestibility differ with +individuals? 669. Why do some foods affect individuals in different +ways? 670. Why is it necessary that the quantity, quality, and character +of the food should vary with different individuals? 671. In what +different ways is the expression "digestibility of a food" used? 672. +Why is it necessary to consider the digestibility of food, as well as +its composition? 673. Does the digestibility of a food necessarily +indicate the economic uses that will be made of it by the body? 674. How +is it possible for one food containing 10 per cent of digestible +protein, and other nutrients in like amounts, to be more valuable than +another food with the same per cent of digestible protein and other +nutrients? 675. How is it possible for one food to contain less total +protein than another food and yet be more valuable from a nutritive +point of view? 676. Why is it necessary to consider the mechanical +condition of a food and its combination with other foods, as well as its +chemical composition? 677. What effect does lack of a good supply of air +have upon the completeness of the digestion process? 678. In what ways +does the digestion of food resemble the combustion of fuel? 679. What is +gained by a study of the digestibility of foods? 680. Why may two foods +of the same general character give different results when used for +nutritive purposes? + + +CHAPTER XVI + +COMPARATIVE COST AND VALUE OF FOODS + +681. To what extent do the nutritive value and the market price of foods +vary? 682. How is the value of one food expressed in terms of another +food? 683. How determine the amount of nutrients that can be procured in +a food for a given sum of money? 684. How compare the amounts of +nutrients that can be procured in two foods for a given sum of money? +685. How is it possible to determine approximately which of two foods is +cheaper, when the price and composition of the foods are known? 686. To +what nutrient is preference usually given in assigning a value to a +food? 687. When the difference in this nutrient between two foods is +small, then the preference is given to what nutrients? 688. At ordinary +prices, what are the cheapest vegetable foods? 689. What are among the +cheapest animal foods? 690. Why is it not possible to determine the +value of a food absolutely from its composition and digestibility? 691. +Why is it necessary to consider the physical as well as the chemical +composition of foods? 692. What proportion of the income of the laboring +man is usually expended for food? 693. What are the most expensive +foods? 694. What foods furnish the largest amount of nutrients at the +least cost? + + +CHAPTER XVII + +DIETARY STUDIES + +695. What is a dietary study? 696. How is a dietary study made? 697. +What is the value of the dietary study of a family? 698. To what extent +does the protein in the dietary range? 699. Why is a scant amount of +protein in a ration undesirable? 700. Why is an excess of protein in the +ration undesirable? 701. What are dietary standards? 702. How are such +standards obtained? 703. Why is it desirable in a ration to secure the +protein and other nutrients from a variety rather than from a few foods? +704. Why is it necessary to consider the caloric value of a ration? 705. +How is this determined? 706. What is a wide nutritive ratio? 707. What +is a narrow nutritive ratio? 708. Why should the amount of nutrients +consumed vary with the work performed? 709. How should the nutrients be +apportioned among the meals? 710. What are some of the most common +dietary errors? 711. What analogy exists between human and animal +feeding? 712. What is gained by the rational feeding of both humans and +animals? 713. What use can be made of the results of dietary studies for +improvement of the dietary? 714. Why is it not possible for animal foods +to compete in economy with cereal and vegetable foods? 715. Is a +well-balanced ration and one containing an ample supply of nutrients +necessarily an expensive ration? 716. Show how it is possible for one +family to spend less money for food than another family, and yet secure +more digestible nutrients and energy. 717. What are some of the most +erroneous ideas as to food values? 718. Why is it necessary to consider +previously acquired food habits in the selection of foods? 719. In +general, what portion of the nutrients of a ration should be derived +from vegetable foods, and what portion from meats? 720. To what extent +may a ration vary from the dietary standards? 721. Why are some +inexpensive foods often expensive when prepared for the table? 722. What +are some of the ways in which the cost of a ration can be decreased +without sacrificing nutritive value? 723. Why do different nationalities +acquire distinct food habits? 724. Why is it not possible to make sudden +and radical changes in the dietary? 725. Why is it not possible for a +dietary which gives ample satisfaction for one class of people to be +applied to another class with equal satisfaction? 726. What relationship +exists between the dietary of a nation and its physical development? +727. What relationship exists between dietary habits and mental +development and vigor? 728. Why is it unnecessary and undesirable to +regulate absolutely the amount of nutrients consumed in the daily +ration? 729. What is the general tendency as to quantity of food and +amount of nutrients consumed? 730. Why do people of sedentary habits +require a different dietary from those pursuing active, out-of-door +occupations? + + +CHAPTER XVIII + +RATIONAL FEEDING OF MAN + +731. What is the object of the rational feeding of man? 732. On what is +it based? 733. How does it compare with the rational feeding of animals? +734. What is a standard ration? 735. How is it determined? 736. To what +extent may the nutrients of a ration vary from the standard? 737. How do +you combine foods to form a balanced ration? 738. What foods are +valuable for supplying protein? 739. What foods supply fats? 740. What +foods are rich in carbohydrates? 741. What other requisites should a +ration have in addition to supplying the necessary nutrients? 742. Why +is it necessary to consider the calorie value of a ration? 743. If a +ration contained an excess of carbohydrates and a scant amount of +protein, how could it be improved? 744. How do you calculate the +nutrients in a fraction of a pound of food? 745. Give the amounts of the +common food materials, as potatoes, bread, butter, milk, and cheese, +ordinarily combined to form a ration. 746. To what extent may foods +differ in composition from the average analysis given? 747. What foods +are subject to the greatest and what foods to the least variation? + + +CHAPTER XIX + +WATER + +748. Why is water regarded as a food? 749. Does it enter chemically into +the composition of plants? Of animals? 750. In addition to serving as a +food, why is water necessary for life processes? 751. In what ways may +water be improved? 752. What are the most common forms of impurities? +753. What are the mineral impurities of water? 754. What is their +source? 755. What effect do some of these minerals have upon the value +of the water? 756. What causes some waters to dissolve limestone? 757. +What are permanently hard waters? 758. To what is temporary hardness in +water due? 759. What is the best way to remove mineral matter from +water? 760. What are the organic impurities of water? 761. What are the +sources of the organic impurities? 762. What change does the organic +matter of water undergo? 763. What becomes of the nitrogen of the +organic matter? 764. What does the presence of nitrates in water +indicate? Nitrites? 765. What is the total solid matter of a water, and +how is it obtained? 766. Define the terms free ammonia; albuminoid +ammonia. 767. What does the presence of chlorine in a surface well water +indicate? 768. Explain natural purification of water. 769. Can natural +purification always be relied upon? 770. Why does the character of the +drinking water affect health? 771. What diseases are mainly caused by +impure drinking water? 772. With what materials in water are the +disease-producing organisms associated? 773. Why should a water of +questionable purity be boiled? 774. State how the boiling should be +done, to be effective. 775. Why should boiled water receive further care +in its storage? 776. What effect does improvement of the water supply of +a city have upon the death rate? 777. How may connections between +cesspools and surface well waters be traced? 778. What impurities do +rain waters contain? 779. Explain the workings of the Pasteur and +Berkefeld water filters. 780. Why must special attention be given to +cleaning the water filter? 781. Explain the processes employed for the +removal of mechanical impurities of water by sedimentation and the use +of chemicals. 782. Why should such purification be under the supervision +of a chemist or bacteriologist? 783. What effect does freezing have upon +the purity of water? 784. Why are precautions necessary in the use of +ice for refrigeration? 785. What are mineral waters? 786. How are +artificial mineral waters prepared? 787. What are the more common +materials used in their preparation? 788. Why should mineral waters be +extensively used only by the advice of a physician? 789. What are some +of the materials used for softening water? 790. Which are the least +objectionable of these materials? 791. Which are the most objectionable? +792. What can you say of the use of ammonia and ammonium carbonate for +softening waters? 793. In washing clothing after contagious diseases, +what materials may be used for disinfecting? 794. Why, in softening +waters for household purposes, must caustic soda, potash, and bleaching +powder be used with caution? 795. Why is it necessary to determine by +trial the material most suitable for softening water? 796. What +advantage, from a pecuniary point of view, results from the improvement +of the water supply of a community? + + +CHAPTER XX + +FOOD IN ITS RELATION TO HOUSEHOLD SANITATION AND STORAGE + +797. What are the compounds usually determined in a food analysis? 798. +Does such an analysis necessarily indicate the presence of injurious +compounds? 799. What are the sources of the injurious organic compounds +in foods? 800. Why is it necessary to consider sanitary condition as +well as chemical composition? 801. What are the sources of contamination +of foods? 802. What is the object of the sanitary inspection of food? +803. How may flies carry germ diseases? 804. Why should food be +protected from impure air and dust particles? 805. Why should places +where vegetables are stored be well ventilated? 806. How may the dirt +adhering to vegetables be the carrier of germ diseases? 807. Why should +the cellar in which food is stored be in a sanitary condition? 808. What +effect does the cleaning of streets and improvement of the sanitation of +cities have upon the death rate? 809. Name the three natural +disinfectants, and explain the action of each. 810. Why must dishes and +utensils in which foods are placed be thoroughly cleaned? 811. Explain +the principle of refrigeration. 812. What kind of ferment action may +take place at a low temperature? 813. Why is some ventilation necessary +in refrigeration? 814. What effect does refrigeration have upon the +composition of food? 815. What relationship exists between unsanitary +condition of soils about dwellings and contamination of the food? 816. +Why should special attention be given to the sanitary disposal of +kitchen refuse? 817. Name the ways in which this can be accomplished. +818. How may foods become contaminated through imperfect plumbing? 819. +Mention the conditions necessary in order to keep foods sanitary. + + + + +REFERENCES + + +The following list of references is given for the use of the student in +case additional information is desired upon some of the subjects +discussed in this work. The list is not intended as a complete +bibliography of the subject of foods. The advanced student will find +extended references in the Experiment Station Record and the various +chemical, physiological, and bacteriological journals. + +1. SNYDER: The Chemistry of Plant and Animal Life. + +2. Minnesota Experiment Station Bulletin No. 54: Human Food +Investigations. + +3. CROSS AND BEVANS: Cellulose. + +4. WILEY: Principles and Practice of Agricultural Analysis, +Vol. III. + +5. Minnesota Experiment Station Bulletin No. 74: Human Food +Investigations. + +6. PARRY: The Chemistry of Essential Oils, etc. + +7. U. S. Department of Agriculture, Farmers' Bulletin No. 142: +Principles of Nutrition and Nutritive Value of Food. + +8. MANN: Chemistry of the Proteids. + +9. Minnesota Experiment Station Bulletin No. 85: Wheat and Flour +Investigations. + +10. ARMSBY: Principles of Animal Nutrition. + +11. SHERMAN: Organic Analysis. + +12. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 43: Digestion Experiments with Potatoes and Eggs. + +13. Unpublished results of author. + +14. U. S. Department of Agriculture, Bureau of Animal Industry Bulletin +No. 49: Cold Curing of Cheese. + +15. WILEY: Foods and Their Adulteration. + +16. Minnesota Experiment Station Bulletin No. 63: Miscellaneous +Analyses. + +17. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +13, Part 8: Canned Vegetables. + +18. LEACH: Food Inspection and Analysis. + +19. U. S. Department of Agriculture, Farmers' Bulletin No. 256: +Preparation of Vegetables for the Table. + +20. U. S. Department of Agriculture Year Book, 1905: Fruit and its Uses +as Food. + +21. Handbook of Experiment Station Work, 1893. + +22. U. S. Department of Agriculture, Division of Chemistry Bulletin No. +94: Studies on Apples. + +23. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +69: Fruits and Fruit Products. + +24. U. S. Department of Agriculture, Farmers' Bulletin No. 203: Canned +Fruits, Preserves, and Jellies. + +25. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +27: Sugar Beet Industry. + +26. SADTLER: A Handbook of Industrial Organic Chemistry. + +27. Minnesota Experiment Station Bulletin No. 86: The Food Value of +Sugar. The Digestive Action of Milk. + +28. HUTCHISON: Food and Principles of Dietetics. + +29. U. S. Department of Agriculture, Farmers' Bulletin No 93: Sugar as +Food. + +30. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 252: Maple Sugar and Sirup. + +31. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +13, Part 6: Sugar, Molasses, Sirup, and Confections. + +32. U. S. Department of Agriculture, Farmers' Bulletin No. 121: Peas and +Beans as Food. + +33. U. S. Department of Agriculture, Farmers' Bulletin No. 122: Nuts as +Food. + +34. Maine Experiment Station Bulletin No. 54: Nuts as Food. + +35. California Experiment Station Bulletins Nos. 107 and 132: +Investigations among Fruitarians. + +36. U. S. Department of Agriculture, Farmers' Bulletin No. 74: Milk as +Food. + +37. U. S. Department of Agriculture, Farmers' Bulletin No. 63: Care of +Milk on the Farm. + +38. U. S. Department of Agriculture, Farmers' Bulletin No. 149: +Digestibility of Milk. + +39. RUSSELL: Dairy Bacteriology. + +40. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +13. Part 1: Dairy Products. + +41. U. S. Department of Agriculture, Farmers' Bulletin No. 131: +Household Tests for Detection of Oleomargarine and Renovated Butter. + +42. U. S. Department of Agriculture, Bureau of Animal Industry Bulletin +No 61: Relation of Bacteria to Flavor of Cheddar Cheese. + +43. Minnesota Experiment Station Bulletin No. 92: The Digestibility and +Nutritive Value of Cottage Cheese, etc. + +44. LAWES AND GILBERT: Experiments with Animals. + +45. U. S. Department of Agriculture, Farmers' Bulletin No. 34: Meats, +Composition and Cooking. + +46. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +13, Part 7: Lard and Lard Adulterants. + +47. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 193: Cooking of Meats as Affecting Digestibility. + +48. U.S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 141: Experiments on Losses in Cooking Meats. See also +Office of Experiment Stations Bulletin No. 102: Losses in Cooking Meats. + +49. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 66: Physiological Effect of Creatin and Creatinin. + +50. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 162: The Influence of Cooking upon the Nutritive Value of +Meats. + +51. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +13, Part 10: Preserved Meats. + +52. RICHARDSON, W. D., Journal of the American Chemical +Society, December, 1907: The Occurrence of Nitrates in Vegetable Foods, +in Cured Meats, and Elsewhere. + +53. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 182: Poultry as Food. + +54. U. S. Department of Agriculture, Farmers' Bulletin No. 85: Fish as +Food. + +55. U. S. Department of Agriculture, Farmers' Bulletin, Experiment +Station Work: Digestibility of Fish and Poultry. + +56. U. S. Department of Agriculture, Farmers' Bulletin No. 249: Cereal +Breakfast Foods. + +57. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +50: Composition of Maize. + +58. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 305: Gluten Flour and Similar Foods. + +59. HAMMERSTON: Physiological Chemistry. + +60. EDGAR: The Wheat Berry. + +61. Minnesota Experiment Station Bulletin No. 90: Composition and Value +of Grains. + +62. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 101: Bread and Bread Making. + +63. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 156: Digestibility and Nutritive Value of Bread and +Macaroni Flour. + +64. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 67: Bread and Bread Making. + +65. University of Nebraska Bulletin No. 102: The Effect of Bleaching +upon the Quality of Wheat Flour. + +66. SNYDER: Wheat Flour and Bread. + +67. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 126: Bread and Bread Making. + +68. LAWES AND GILBERT: Experiments on Some Points in the +Composition of the Wheat Grain, of the Product in the Mill and Bread. + +69. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +13, Part 5: Baking Powders. + +70. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +13, Part 2: Spices and Condiments. + +71. Food Standards: U. S. Department of Agriculture. See Annual Reports +of the Association of Official Agricultural Chemists. + +72. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 21: Methods and Results of Investigations on the Chemistry +and Economy of Foods. + +73. U. S. Department of Agriculture, Bureau of Chemistry Bulletin No. +13, Part 7: Tea, Coffee, and Cocoa Preparations. + +74. The Respiration Calorimeter: Year-book U. S. Department of +Agriculture, 1904. + +75. Year Book U. S. Department of Agriculture, 1902: Cost of Food as +Related to its Nutritive Value. + +76. See U. S. Department of Agriculture, Office of Experiment Stations +Bulletins Nos. 82, 71, 129, 116, 37, 55, 150. See also other bulletins +of the Office of Experiment Stations. + +77. CHITTENDEN: Physiological Economy in Nutrition. + +78. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 98: Effect of Severe and Prolonged Muscular Work on Food +Consumption. + +79. HENRY: Feeds and Feeding. + +80. U. S. Department of Agriculture, Office of Experiment Stations: +Dietary Studies in Chicago Bulletin No. 55. + +81. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 116: Dietary Studies in New York City. + +82. U. S. Department of Agriculture, Farmers' Bulletin No. 119: Banana +Flour. + +83. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 159: Digest of Japanese Investigations on the Nutrition of +Man. + +84. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 150: Dietary Studies at the Government Hospital for the +Insane, Washington, D.C. + +85. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 149: Studies on the Food of Maine Lumbermen. + +86. U. S. Department of Agriculture, Office of Experiment Stations +Bulletin No. 143: Studies on the Digestibility and Nutritive Value of +Bread at the Maine Experiment Station. + +87. U. S. Department of Agriculture, Office of Experiment Stations, +Experiment Station Work, Vol. III: Wells and Pure Water. + +88. U. S. Department of Agriculture, Farmers' Bulletin No. 88: Pure +Water on the Farm. + +89 Mineral Impurities in Water. See various bulletins of the California +and New Mexico Agricultural Experiment Stations. + +90. MASON: Examination of Water. + +91. Department of the Interior, U. S. Geological Survey: The Quality of +Surface Waters in Minnesota. + +92. FUERTES: Water and Public Health. + +93. U. S. Department of Agriculture, Farmers' Bulletin No. 124: +Distilled Drinking Water. + +94. TURNEAURE AND RUSSELL: Public Water Supplies. + +95. VAUGHAN AND NOVY: Ptomains and Lencomains. + +96. U. S. Department of Agriculture, Bureau of Entomology, Circular No. +71: House Flies. + +97. ELLEN H. RICHARDS AND S. MARIA ELLIOTT: The Chemistry of +Cooking and Cleaning. + +98. Dr. WOODS HUTCHINSON, _Saturday Evening Post_, 1908: The +Real Angels of the House. + +99. HARRINGTON: Practical Hygiene. + +100. PRICE: Handbook of Sanitation. + + + + +INDEX + + + Air, infection from impure, 287. + pure, disinfectant, 290. + + Albuminoids, 23. + + Alkaloids, 24. + + Allspice, 202. + + Almonds, 77. + + Alum baking powder, 188. + + Amids and Amines, 23. + + Animal and vegetable foods, economy of, 250. + + Animal foods, digestibility of, 220. + + Apparatus used in experiments, 301. + + Apples, 49. + pectose from, 307. + + Ash, of foods, 4. + elements of plants, 5. + + Asparagus, 43. + + Available energy, 217. + nutrients, 216. + + + Bacteria in food, 32. + + Baking powder, composition of, 186. + cream of tartar, 187. + phosphates, 189. + alum, 189. + inspection of, 191. + fillers, 191. + home-made, 191. + testing for alum, 315. + testing for ammonia, 316. + testing for phosphoric acid, 316. + + Baking tests, 153-314. + + Barley preparations, 128. + + Beans, composition, 71. + digestibility, 72. + removal of skins, 72. + string, 73. + use of, in dietary, 74. + + Beef, 101. + extracts, 110. + + Beets, 41. + + Beverages, composition, 213. + + Bleaching of flour, 155. + + Bolting cloth, 138. + + Bread and bread making, 158-185. + leavened and unleavened bread, 158. + chemical changes during making, 159. + losses during bread making, 160. + production of carbon dioxide, 163. + production of alcohol, 163. + production of soluble carbohydrates, 165. + production of acids, 166. + production of volatile compounds, 167. + production of volatile nitrogenous compounds, 172. + wheat proteids, part taken by, 169. + oxidation of fat, 173. + starch, influence of, addition of, 173. + composition of bread, 174. + temperature of flour, 176. + use of skim milk, 176. + process of bread making, 177. + digestibility of bread, 178. + graham bread, use in the dietary, 179. + white and graham bread compared, 180. + mineral content of, 182. + new and old, 183. + action of heat on, 184. + different kinds of, 184. + + Breakfast foods, 121-132. + + Broth, 109. + + Butter, composition, 91. + digestibility, 91. + adulteration, 92. + coloring, 92. + renovated, 92. + water in, 305. + + Buttermilk, 88. + + + Cabbage, 41. + + Candies, 69. + + Canned meats, 118. + vegetables, 46. + peas, 75. + + Carbohydrates defined, 8. + + Carrots, 40. + + Cauliflower, 41. + + Cellars, storage of food in, 283. + + Cellulose and properties, 8. + + Cereals, 121-132. + preparation of, 121. + cost of, 121. + value of, 131. + use of, in dietary, 131. + corn preparations, 122. + oat preparations, 124. + wheat preparations, 126. + barley preparations, 128. + rice preparations, 129. + predigested, 130. + phosphates in, 131. + mineral matters of, 131. + coffees, 210. + + Cesspools, 289. + + Cheese, 92-96. + general composition, 92. + digestibility, 93. + use of, in dietary, 94. + cottage, 95. + different kinds of, 95. + adulteration, 96. + + Chemical changes during cooking, 27-30. + + Chemicals, use of, in preparation of foods permitted, 36. + + Chestnuts, 76. + + Chicory, detection in coffee, 319. + + Chocolate, 212. + adulteration of, 213. + + Cinnamon and cassia, 201. + + Cloves, 201. + + Coal tar dyes, testing for, 308. + + Cocoa, 210. + + Cocoanuts, 77. + + Coffee, composition of, 207. + detection of chicory in, 319. + glazing of, 208. + substitutes, cereal, 210. + types of, 209. + + Combustion of foods, 6. + + Cooking, changes during, 27. + chemical, 27-30. + physical, 30-32. + bacteriological, 32. + + Corn, sweet, 41. + preparations, 122. + + Cream, 87. + + Cream of tartar, 187. + + Crude fiber of foods, 9. + + Crude protein, 21. + + Cucumbers, 42. + + + Dairy products, 80-97. + use of, in dietary, 96. + + Dextrose, 64. + + Dietary standards, 245. + + Dietary studies, 244-260. + object of, 244. + mixed, desirable, 250. + of families compared, 253. + in public institutions, 259. + + Digestibility of foods, 214. + of animal foods, 220. + of vegetable foods, 222. + + Digestion, combination of foods, 223. + factors influencing, 223. + amount of food, 224. + method of preparation of food, 225. + mechanical condition of foods, 226. + psychological factors, 230. + individuality, 229. + + Digestion and health, 219. + + Dishcloth, unclean, 292. + + Disinfectants, 281, 289, 295. + + Drying of foods, 2. + + Dry matter, 2. + + + Egg plant, 44. + + Eggs, 114-118. + composition, 114. + digestibility, 116. + cooking of, 116. + use of, in dietary, 117. + + Elements in foods, 7. + + Energy, available, 217. + + Energy value of rations, 246. + + Entire wheat, 145. + + Essential oils, 15. + occurrence, 15. + composition of, 16. + food value, 16. + + Esthetic value of foods, 36. + + + Fat, occurrence in food, 12. + composition, 13. + physical properties, 14. + food value, 14. + individual fats, 14. + oxidation of, during bread making, 173. + + Ferments, soluble, 34. + insoluble, 34. + + Figs, 54. + + Fish, 113. + + Flavoring extracts, 56. + + Flavors, composition of, 48. + occurrence of, 49. + food value, 49. + + Flies, contamination of food by, 286, 295. + + Foods, 215. + digestibility of, 215. + mechanical condition of, 226. + palatability of, 228. + physiological properties of, 228. + ash of, 4. + predigested, 130. + sodium chloride in, 4. + cost of, 231. + market price and nutritive value, 231-234. + composition of, 234-263. + comparative nutritive value, 231. + economy of production, 250. + habits, 250. + notions, 252. + relation to mental and physical vigor, 258. + amount consumed, 262. + injurious compounds in, 284. + contamination of, 284, 292. + sanitary inspection of, 286. + storage in cellars, 288. + infection from impure air, 287. + utensils for storage, 291. + raw, 27. + cheap and expensive, 252. + + Fruits, composition of, 48. + canned, 54. + dried, 54. + canned and adulterated, 55. + + Fruit extracts, 56. + + Fruit flavors, 55. + + + Ginger, 200. + + Gliadin, 314. + + Gluten, addition of, to flour, 173. + moist and dry, 314. + + Gluten properties of flour, 151. + + Graham bread, 179. + use in dietary, 180. + + Graham flour, 144. + + Grape fruit, 51. + + Grapes, 53. + + + Heat, action on foods, 30. + + Hickory nuts, 77. + + Honey, 68. + + + Ice, 279. + + Inspection of food, 286. + + Inversion of sugar, 64. + + + Kitchen refuse, 294. + + Koumiss, 88. + + + Laboratory practice, 299. + + Lard, 106. + substitutes, 107. + + Legumes, 71-76. + + Lemon extract, testing, 307. + + Lemons, 51. + acidity of, 305. + + Lettuce, 42. + + + Macaroni flour, 148. + + Mace, 202. + + Malted foods, 121. + + Maple sugar, 62. + + Meals, number of, per day, 248. + + Measuring, directions for, 302. + + Meat broth, 109. + + Meats, 98-120. + general composition, 98. + proteids of, 99. + fat of, 100. + water of, 98. + texture of, 107. + cooking of, influence of, on composition, 108. + extractive materials, 110. + smoked, 111. + boric acid in, 312. + saltpeter in, 111. + canned, 118. + + Melons, 43. + + Microscope, use of, 304. + + Milk, importance in dietary, 80. + general composition, 80. + souring of, 86. + condensed, 87. + digestibility, 81. + sanitary condition, 82. + certified milk, 84. + pasteurized, 84. + color of, 85. + preservatives in, 86. + goat's, 88. + human, 89. + adulteration of, 89. + prepared, 88. + formaldehyde in, 310. + + Mineral matter, 4. + in ration, 5. + + Mineral waters, 279. + + Miscellaneous compounds, 16. + + Mixed nitrogenous compounds, 25. + + Mixed non-nitrogenous compounds, 16. + + Moisture content of foods, variations in, 1. + + Moisture in foods, how determined, 2. + + Molasses, 65. + + Mustard, 199. + testing for turmeric, 318. + + Mutton, 103. + + + Nitrates in foods, 45. + + Nitrites in foods, 111. + + Nitrogen free extract, 11. + defined, 11. + composition, 12. + how determined, 12. + variable character of, 12. + + Nitrogenous compounds, 17. + general composition, 17. + + Non-nitrogenous compounds, classification of, 7. + + Nutmeg, 202. + + Nutrients, available, 216. + + Nutritive value of nitrogenous compounds, 16. + starch, 9. + sugar, 11. + nitrogen free extract, 11. + fat, 12. + protein, 19. + amids, 23. + + Nuts, 76-79. + use of, in dietary, 78. + + + Oat preparations, 124. + + Oleomargarine, 92. + detecting, 310. + + Olive oil, testing, 308. + + Olives, 54. + + Onions, 42. + + Oranges, 50. + + Organic acids, 15. + occurrence in foods, 15. + influence on digestion, 15. + use in plant economy, 15. + production during germination, 15. + + Organic compounds, classification of, 7. + + Organic matter, 6. + + Oysters, 114. + + + Palatability of food, 228. + + Parsnips, 40. + + Peaches, 53. + + Peanuts, 76. + fat from, 309. + + Peas, 74. + canned, 75. + + Pectose substances, 11. + + Pepper, 198. + + Phosphate baking powders, 189. + + Physical changes during cooking, 30. + + Physiological properties of foods, 228. + + Pistachio, 77. + + Plumbing, sanitary, 297. + + Plums, 53. + + Pork, 104. + + Potatoes, 37. + composition, 39. + digestibility, 38. + nutritive value, 38. + sweet, 39. + + Poultry, 112. + + Predigested foods, 130. + + Protein, composition of, 19. + properties of, 19. + combinations of, 20. + types of, 20. + crude, 21. + food value of, 22. + amount of, in ration, 246. + + Psychological factors in digestion, 230. + + Pumpkins, 45. + + + Rational feeding of man, 261-267. + + Rations, wide and narrow, 245. + standard, 261. + object of, 261. + examples of, 264. + requisites of, 266. + protein requirements of, 246. + energy value of, 246. + + References, 350. + + Refrigeration, 292. + + Refuse, disposal of, 294. + + Renovated butter, 92. + + Review questions, 323. + + Rice preparations, 129. + + + Saccharine, 70. + + Saltpeter in meats, 111. + + Sanitary condition of vegetables, 45. + + Sanitary inspection of food, 286. + + Sausage, 111. + + Sodium chloride in foods, 5. + + Soil, sanitary condition of, 294. + + Spices, 212. + + Spinach, 42. + + Squash, 45. + + Starch, 9. + occurrence, 9. + composition, 9. + properties, 10. + food value, 10. + influence of heat on, 10. + + Strawberries, 52. + + Sugar, defined, 11. + beet, 58. + cane, 58. + commercial grades, 58. + manufacture of, 59. + sulphur in, 59. + digestibility of, 59. + value of, in dietary, 61. + adulteration of, 63. + maple, 62. + dextrose, 64. + + Sunlight as a disinfectant, 290. + + Sweet potatoes, 39. + + Syrups, 66. + sorghum, 66. + + + Tea, 203-206. + black, 203. + green, 204. + composition of, 214. + judging of, 205. + adulteration of, 206. + physiological properties of, 206. + examination of leaves, 318. + + Toast, 184. + + Tomatoes, 43. + + + Underfed families, 251. + + + Vanilla extract, testing, 307. + + Veal, 102. + + Vegetable foods, 222. + + Vegetables, 37-47. + edible portion, 47. + canned, 46. + sanitary condition of, 45. + digestibility of, 222. + + Vinegar, 193-197. + preparation of, 193. + different kinds of, 195. + adulteration of, 196. + solids, 316. + specific gravity, 317. + acidity, 317. + + Volatile matter, 6. + + + Water, drinking, 268-283. + importance, 268. + impurities in, 269. + mineral impurities, 270. + organic impurities, 271. + purification of, 272-278. + analysis, 271. + and typhoid fever, 273. + improvement of, 276. + boiling of, 276. + filtration of, 277. + distillation of, 278. + materials for softening water, 280. + testing purity of, 320. + + Water in foods, 1. + how determined, 1. + + Water supply, economic value, 282. + + Waters, mineral, 279. + + Weighing, directions for, 302. + + Wheat cereal preparations, 126. + + Wheat flour, 133. + spring and winter wheat flour, 133. + starchy and glutenous, 135. + composition of, 136. + process of milling, 136-140. + patent, 142. + grades of, 142. + composition of, 143. + ash content, 145. + graham, 145. + entire wheat, 145. + by-products, 146. + aging and curing, 147. + macaroni, 148. + color, 148. + granulation, 149. + capacity to absorb water, 150. + gluten, properties of, 151. + unsoundness of, 152. + baking tests, 153. + bleaching of, 155. + adulteration of, 156. + nutritive value of, 157. + water in, 304. + ash in, 305. + acidity of, 313. + moist and dry gluten, 314. + + + Yeast, action of, 161. + compressed, 162. + dry, 163. + + + + +BY HARRY SNYDER, B.S. + + Professor of Agricultural Chemistry, University of Minnesota, and + Chemist of the Minnesota Agricultural Experiment Station + +The Chemistry of Plant and Animal Life + +_Illustrated. 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