v TEXAS AGRICULTURAL EXPERIMENT STATION C. H. McDOWELL, ACTING DIRECTOR College Station, Texas BULLETIN NO. 680 AUGUST, 1946 COMPOSITION, DIGESTIBILITY AND ENERGY VALUES OF SOME HUMAN FOODS G. S. FRAPS Division 0f Chemistry AGRICULTURAL AND MECHANICAL COLLEGE OF TEXAS GIBB GILCHRIST, President D71-846-3M-L180 [Blank Page in Original Bulletin] This bulletin presents the average chemical composition of a number of human foods of which Texas analyses were made, human digestion experiments on cabbage, collards, oat meal and string beans, the average digestibility of human foods as compiled from the literature, factors for calculating the metabolizable energy and productive energy of human foods, a comparison of the fuel values as usually calculated with the metabolizable energy, and the productive energy for the human diet as compared with allowances recommended of metab- olizable energy. The calories of fuel values as ordinarily calculated are too low for many foods of animal origin and too high for foods of vegetable origin on account of the assumption that all human foods have the same digestibility. The metabolizable energy values as here calculated give more nearly correct results. The productive energy is measured by the energy stored as protein and fat by growing chickens from that part of the ration fed in excess of maintenance. The productive energy values of human foods are not always in the same proportion to the metabolizable energy. The relative energy values of human foods are probably given more nearly correctly by the productive energy values than by the metabolizable energy values. CONTENTS Page Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 g Constituents of Human Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Composition of Some Human Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7 g Compilations of Analyses of Human Foods . . . . . . . . . . . . . . . . . . . . . . . . .. 11 a Digestibility of Human Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12 Texas Digestion Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 l Results of the Texas Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13 Average Digestibility of Foods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14 Digestibility of Crude Fiber . . . . . . . . . . . . . . . > . . . . . . . . . . . . . A . . . . .. 20 Metabolizable Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21 Productive Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 27 Energy-production Coefficients for Human Foods . . . . . . . . . . . . . . . . . . .. 28 Productive Energy Values of Some Human Foods . . . . . . . . . . . . . . . . . . .. 31 Productive Energy of Wheat Flour. . .- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 31 o Productive Energy of Fats and Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33 A Energy Cost of Utilization of Food Nutrients . . . . . . . . . . . . . . . . . . . . . . .. 35 Daily Allowances for Calories of Metabolizable Energy and of Produc- tive Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37 Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 38 _ Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 38 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 40 v 1 BULLETIN NO. 680 AUGUST, 1946 COMPOSITION, DIGESTIBILITY AND ENERGY VALUES OF SOME HUMAN FOODS G. S. Fraps, Collaborating Chemist, Division 0f Chemistry This publication deals chiefly with the energy values of human foods. Students of animal nutrition have for a long time recognized that one * pound of the digestible nutrients of one feed is not necessarily equal in h energy value to one pound of the digestible nutrients of some other feed; for example, one pound of the digestible nutrients of straw has a much "1 . lower energy value to ruminants than one pound of the digestible nutrients Wran- of corn. Books of Kellner (41), Armsby (1), Fraps (18), Morrison (49), Brody (9) and others have discussed this subject, and scientific papers by Armsby, Fraps, Forbes, H. H. Mitchell, Brody and others have dealt p with various aspects of the subject of the net energy or productive T. energy values of feeding stuffs. The net energy concept has received little application to human foods ~and nutrition. A Bankhead-Jones project on the productive values of human foods at the Texas Agricultural Experiment Station was approved November 1, 1935. The object was to study the productive values of human food. The plan proposed to use animals chiefly, although some b human experiments might be made. The animals were to be grown on the foods to be tested and the productive values of the foods estimated 7from the gains of protein and fat. Digestion experiments were to be made. The effect of various factors on the productive values were to be estimated. Productive values were to be calculated from the data secured as well as from any other data that could be available. A number of publications have been made on various phases of this ' project, and on a similar project relating to animal feeds (22, 28, 29, 30, 32). This bulletin deals with analyses of some human foods, a few digestion experiments, average digestion coefficients, fuel values and metabolizable ~ energy values and factors for calculating them, factors for calculating a productive energy, the productive energy of some human foods, and other i data relative to the subject especially as applied to human nutrition. Constituents of Human Foods , . In the ordinary analysis of animal feeds, determinations are made of _protein, ether extract (fat), water, ash and crude fiber. The sum of these is subtracted from 100 and the difference is termed nitrogen-free extract. In the similar analysis of human foods, the determination of crude fiber is often omitted, and the sum of the protein, ether extract, l water and ash subtracted from 100 gives what is termed carbohydrates o (12, 54). The term carbohydrates as thus used is the sum of the nitrogen- 6 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION free extract and crude fiber, if crude fiber is present. The term carbo- hydrate as used by chemists means compounds containing carbon com- bined with hydrogen and oxygen in the proportions to form water, and as used above for human foods, is incorrect, because although true carbo- hydrates are present, organic acids, lignins and other non-carbohydrates are also contained in many human foods. Crude fiber is not present at all, or in very small percentages inmany human foods, such as meat, milk, eggs, white bread, white flour and potatoes. Crude fiber is, however, present in appreciable proportions in vegetables, fruits and nuts. The average percentage of crude fiber in the so-called carbohydrates in some human foods is given in Table 1. Vegetable foods may also contain appreciable percentages of uronic acid, as is shown in_ Table 2 Table 1. _ Percentage of crudefiber in percentage of so-called carbohydrates Crude Crude Fiber Fiber Percent Percent Nuts Almond 13 Pumpkin 19 Blrlazil nuts 19 Turnip roots 15 C estnut ' 3 - Coconut 21 A Finns Peanut 11 Pp?’ es 7 Pecans 17 runes 2 Walnut, English 13 235:3 g Vegetables 4 Grapes 4 Potato, white 2 Olive 30 Potato, sweet 3 Pears 8 IStiustarfil greens 20 Persimmon 10 pinac 19 Chard leaves & stalks 20 Cereals Turnip greens 23 Barley’ pearled 1 Broccoli 24 Com 3 Cabbage 19 Oat glee‘ 2 Celery 19 Rye our 3 Collards 17 Bread, Graham 2 Lettuce 21 Graham flour 2 Squash 13 wheat 2 Tomato 15 Wheat bran 9 Okra 14 Legumes Beet roots 9 Beans, dried 7 Candis 12 Peas, dried 9 Eggplant 16 from Phillips, Gross and Browne (51). Uronic acids are decomposed by boiling with acid into carbon dioxide ‘and furfural, and hence may be classed as pentosans, which they are not. The sugars and starches, which Table 2. Uronic acid anhydride in certain foods, dry basis Food percent Food Percent Melon, honey dew 3.60 Squash, summer 10,64 Cantaloupe 4,00 Cabbage leaves 11.16 Lima. beans 4.20 Cauliflower 12,56 Peas 4.88 Radish tops 12,72 Cucumber, peeled 8.32 Kale 14,04 Asparagus stalks 9.16 Lettuce leaves, head 14.20 Asparagus tips 9.88 Beet tops 14.52 Carrots 10.24 Carrot tops 16.28 constitute high percentages of the nitrogen-free extract, are accompanied by appreciable amounts of pentosans and residual nitrogen-free extract in some foods (21), s ._..__ . t- 1.4.1.." ~ 2 COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 7 The protein in many human foods consists almost entirely of proteids but green vegetables and fruits contain appreciable percentages of non- proteids. The percentage of nitrogen is not the same in all proteids. The usual method of ascertaining the percentage of protein is to determine nitrogen and multiply the percentage by a factor: 6.25 is required by many feed control laws, and is usually used. The factor 5.70 is some- times used for cereals and cereal products, and the factor 6.38 for dairy products (40). The factor used should always be stated. ‘Va-Hm !W;W“'*]:P'."f"7’vyr 4.. —~r> .. Wm. Composition of Some Texas Human Foods The average chemical composition of some human foods in terms. of protein, ether extract, and other constituents, from analyses made in this laboratory, are given in Table 3. The analyses were made by the methods Table 3. Composition of some human foods, Texas analyses ~03 . s: *5 a u; Q Q _,_, O '- Q O s 5; ~*.= g a...» §v~w.—»-vvv<~n"§(""r17r—wv COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 13 The samples for analysis were weighed and dried in a water bath for about 48 hours, then exposed to room temperature and moisture before weighing before preparation for analysis. A The subjects had a three-day preliminary period and a two-day collec- i. tion period. They were furnished covered pails fitted with a weighed 5 evaporating dish and the excrements were brought to the laboratory and _ dried. The dishes and dried excrements were then weighed and the weights _of the dishes subtracted. The excrements were combined and ground for analysis. Results of the Texas Experiments The composition of the foods used in the digestion experiments are V given in Table 5, and the digestibility in Table 6. The coefficients of digestibility are also incorporated in the averages in Table 8. Table 5. Composition of foods used in human digestion experiment Nitrogen- Protein Ether Crude free Water Ash percent extract fiber extract percent percent percent percent percent Beans, string . . . . . . . . . . . . .. 1.16 .13 1.04 4.40 92.44 .83 Cabba e, boiled . . . . . . . . . . .. 1.09 .08 .81 4.18 93.33 .51 Collar s . . . . . . . . . . . . . . . . . .. 3.13 .54 1.51 3.52 88.44 2.36 l Oatmeal, cooked . . . . . . . . . .. 2.12 0.29 0.21 9.56 87.38 .44 Bread, average of 3 samples. . 10.90 3.26 .30 47.63 36.00 1.91 Butter, average of 3 samples. . . . . . . . . . 82.04 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Milk, average of 8 samples .. . 3.93 5.27 0 5.13 84.93 .74 Table 6. Percentage digestibility of the constituents of some human foods -——Texas experiments Nitrogen- Protein Ether Crude free percent extract fiber extract percent percent percent Oat meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 64 57 100 K ~Oat meal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 100 0 100 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 82 29 100 String beans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 100 80 77 String beans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 100 88 92 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 100 84 85 . Cabbage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4s 100 3s 75 Cabbage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 100 67 84 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 100 52 80 Collards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 100 82 0* Collards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 100 73 45 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 100 78 45 ‘Excluded from average. c v 14 Average Digestibility of Foods In connection with the work here reported, human digestion experiments were compiled and averaged so far as they were available, as had pre- viously been done for digestion experiments with ruminants (19), with BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION chickens (25) and with rats (27). The average digestibility for animal and vegetable fats and oils by human experiments are given in Table 7, including some digestion ex- " periments with rats. Coeflicients of digestibihty for other foods and some mixtures are given in Table 8. Table 9 contains the references to the experiments from which the data in Tables 7 and 8 are derived. Table 7. Average digestibility of fats and oils, compiled Ether extract, Number References percent averaged Table 9 Almond oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 4 39 Apricot oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 4 44 Brazil nut oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 3 39 Beef fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 1O 34 Brisket fat . . . . . . . . 97 7 37 Butter, cow . . . . . . . 93 19 34, 56, 82 Butter, goats . . . . . . 98 4 38 Butternut oil . . . . . . 95 3 39 Cantaloupe seed.. . 98 3 44 Charlock oil. . . .. . . 99 4 42 Cherry kernel Oil. . . 98 4 44 Chicken fat . . . . . . . 97 8 37 Coconut oil . . . . . . . 98 7 34 Coconut butter. .. . 100 2 50 Corn oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 7 42 Corn oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 7 83 Corn oil, hydrogenated, m. p. 33° C. . . .. 99 5 83 Corn oil, hydrogenated, m. p. 43° C . . . . . . 95 5 83 Corn oil, hydrogenated, m. p. 50° C. .. .. . 81 5 83 Corn oil and other oil . . . . . . . . . . . . . . . . . . 93 27 37, 82 Cottonseed oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 7 36 Cottonseed oils, blended . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 l0 83 Cottonseed oil, hydrogenated . . . . . . . . . . . . . . . . . . . . . . . . . . 96 5 52, 62 Cottonseed oil, hydrogenated, m. p. 35° C . . . . . . . . . . . . . . . 97 . . . . . . . . . . 83 Cottonseed oil, hydrogenated, m. p. 46° C . . . . . . . . . . . . . . 95 . . . . . . . . . . 83 Deer fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 3 83 Goose fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .' . . . . . . . 95 7 37 Hard palate fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 94 3 36 Hickory nut oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 99 4 39 Horse fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 . . . . . . 94 3 38 Kid fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 3 38 Lard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 13 34, 52, 54 Lard substitute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 2 57 lVIargarin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 4 56 Mustard seed oil (Japanese) . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 3 42 Mutton fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 7 34 Nut butter and milk fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 22 55 Oleo oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 8 38 Olive oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 l0 36 Ox marrow fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 4 38 Ox tail fat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 3 38 Peach kernel oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 3 44 Peanut oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 7 36 Peanut oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 9 83 Peanut oil, hydrogenated, m. p. 37° C . . . . . . . . . . . . . . . . . . 98 5 83 Peanut oil, hydrogenated, m. p. 43° C . . . . . . . . . . . . . . . . . . 97 5 83 Peanut oil, hydrogenated, m. p. 50° C . . . . . . . . . . . . . . . . . . 92 4 83 Peanut oil, hydrogenated, m. p. 52.4° C . . . . . . . . . . . . . . . . 79 3 83 Pecan oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 4 39 Pumpkin seed oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 2 44 u,“ a.i__.-.._.._.1.=.1..__.<~...i... lxxgraa,_i.iu..i__.s;ti<......_.i.lau__.._._n . . Al .\_ MAME “u. ndnmi.@i.ri.._‘_.»n_..i.._nax,maimnam_mmahmmni “midi. COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 15 Table 7. Average digestibility of fats and oils, compiled-Continued Ether extract, Number References percent averaged Table 9 éRape seed oil . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . 99 4 42 Sesame oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 5 36 l-oybean oil . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . . . . . 98 7 42 Sunflower seed oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 4 42 Tea seed oil . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . 91 1 62 Tomato seed oil . . . . . . . . . . . . . . . . . . . . . . 96 3 44 Turtle, green, fat . . . . . . . . . . . . . . . . . . . . . 99 3 39 alnut (black) oil . . . . . . . . . . . . . . . . . . . . 98 4 39 “Walnut (English oil . . . . . . . . . . . . . . . . . . 98 3 39 Watermelon see oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 3 83 Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96.0 Table 8. Average digestibility of human foodsfother than fats and oils, compiled Ether Carbo- Protein, extract, hydrates, Number References percent percent percent averaged Table 9 Amurone . . . _ . . . . . . . . . . . . . . . . . . . 97 . . . . . . . . . . 97 1 68 {Aieurone biscuits . . . . . . . . . . . . . . : 91 . . . . . . . . . . 97 2 68 Annon s . . . . . . . . . . . . . . . . . . . . . . . 84 88 92 6 24, 64 _ \ me, dried . . . . . . . . . . . . . . . . . . . . 16 35 68 4 31 Apples . . . . . . . . . . . . . . . . . . . . . . . . . 72 86 95 9 27 Wlpples, dried (rats) . . . . . . . . . . . .. O 36 94 1 84 [Apple sauce . . . . . . . . . . . . . . . . . . . . 19 98 99 2 77 -_Arrowhead, soybean sauce... . . . . 9O 72 98 1 31 Artichoke tubers (rats) . . .. . . . . . . 27 0 9O 1 84 "Asparagus, dried (rats) . . . . . . . . .. 84 65 81 2 84 yBacon . . . . . . . . . . . . . . . . . . . . . . . . . 92 96 . . . . . . . . . . 6 10 ' Bananas . . . . . . . . . . . . . . . . . . . . . . . 75 82 94 8 27 ; arley . . . . . . . . . . . . . . . . . . . . . . . . . 69 . . . . . . . . . . 97 2 13 >Barley, rolled, and soybean sauce. 69 . . . . . . . . . . 99 2 31 Barley and beef soup . . . . . . . . . . . . 51 60 93 1 31 ~ey bread and butter . . . . . . . . . 78 95 91 1 59 Beans, navy, cooked (rats) . . . . . . . 74 61 92 4 84 ns . . . _ . . . . . . . . . . . . . . . . . . . . . 80 80 96 3 9 _1 ns, kidney . . . . . . . . . . . . . . . . .. 77 6O 94 8 32 g‘! ~- navy (calc.) . . . . . . . . . . . . . 76 41 94 5 9 p l »' ns, navy . . . . . . . . . . . . . . . . . . . 78 51 96 6 32 ~ *1 s, soybean sauce . . . . . . . . . . . 66 36 90 2 31 s,string.................., 43 100 85 2 85, _ ns, string (rats) . . . . . . . . . . . .. . 53 21 89 2 84. -~ as ham urger (calc.) . . . . . . . . 96 96 . . . . . . . . . . 2 17 ié: - r, m shoulder (boiled) . . . .. . 91 91 . . . . . . . . .. a s3 $5: t, lean, fried . . . . . . . . . . . . . . . .. 97, 9s . . . . . . . . .. 3 33 f, lean round (boiled 1 hr. 80- in 5° C.) . . . . . . . . . . . . . . . . . . . . 97 89 . . . . . . . . . . 5 33 Beef, lean (boiled 2 hr. in 80 to ° . . . . . . . . . . . . . . . . . . . . . 97 90 . . . . . . . . . . 5 33 a f, lean (boiled 3 hr. in 80 to -‘ 85° C. . . . . . . . . . . . . . . . . . . . . 99 97 . . . . . . . . . . 2 33 f, lean round (roasted) . . . . . . . . 99 99 . . . . . . . . . . 3 33 f, ribs (roasted) . . . . . . . . . . . . . 99 99 . . . . . . . . . . 7 33 - f, roasted . . . . . . . . . . . . . . . . . . . 98 88 . . . . . . . . . . 5 14, 49 f, round (pan boiled) . . . . . . . . 98 98 . . . . . . . . . . 3 33 ' -- roots . . . . . . . . . . . . . . . . . . . . . 72 100 97 3 77 a- ’t roots (rats) . . . . . . . . . . . . . . . . 48 25 92 5 84 ‘g- ' . . . . . .. 85 89 94 3 27 p» =- aeurone ayer o, sugar 1% _ 10%)..., . . . . . . . . . . . . . . . . . . . 86 . . . . . . . . .. 96 2 68 flread, 2/3 wheat, 1/3 barley .. . . . 82 94 99 1 74 rBread, black . . . . . . . . . . . . . . . . . . . 83 72 73 3 51 .1» d, black . . . . . . . . . . . . . . . . . .. 66 . . . . . . . . .. 86 2 71 _h d, brown (coarse) . . . . . . . . .. 79 . . . . . . . . . . . . . . . . . . .. 4 73 t. 1* 16 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION Table 8. Average digestibility of human foods other than fats and oils, compiled—(‘lontinued Ether Cabro- Protein , extract, hydrates, N um ber References percent percent percent averaged Table 9 Bread, graham . . . . . . . . . . . . . . . . . 79 65 92 40 6, 19, 20, 22, 26, 28, _ 30, 70 Bread, 2/3 wheat, 1/3 maize. . . . . 87 95 99 1 74 Bread, Pumpernickel . . . . . . . . . . . . 48 . . . . . . . . . . 9O 1 68 Bread, war, 1917 . . . . . . . . . . . . . . . . 89 96 99 1 74 Bread, wheat and rye with yeast. . 81 . . . . . . . . . . . . . . . . . . . . 4 14 Bread, 70% milled from fine rye and wheat flour . . . . . . . . . . .. 86 95 98 2 70 Bread, white . . . . . . . . . . . . . . . . . .. 87 75 98 77 6, 14, 19, 22, 26, , 30, 50, 51, 61, 70, 71, 73, 74 Bread, white (rats) . . . . . . . . . . . . . . 85 91 99 4 84 Bread, bran and flour . . . . . . . . . . . . 86 . . . . . . . . . . 94 3 30 Bread, ger_m flour. . . ._ . . . . . . . . . . . 90 . . . . . . . . . . 98 3 30 Bread, white (70% milled). . . . . 94 97 99 2 70 Bread, white (finely ground zwie- bach flour, 70% milled) . . . . . . 81 . . . . . . . . . . 97 2 68 Bread, white flour (75% milled). . 88 . . . . . . . . . . . . . . . . . . . . 12 66 Bread, white flour (80% milled). . 87 . . . . . . . . . . . . . . . . . . . . 6 61 Bread, white flo_ur (85% milled). . 82 . . . . . . . . . . . . . . . . . . . . 6 66 Bread, 80% milled (corn 82%, flour 187) . . . . . . . . . . . . . . . . . 85 . . . . . . . . . . . . . . . . . . . . 6 66 Bread, white flour (20% starch) . . . 84 . . . . . . . . . . 98 3 17 Bread, white, war . . . . . . . . . . . . . . . 89 96 99 1 75 Bread, whole wheat . . . . . . . . . . . . . 83 64 95 40 6, 14, 19, 22, 26, , 3g, 34, 61, Bread, zwiebach aleurone . . . . . . . . 86 . . . . . . . . . . 97 2 68 Bread, zwiebach, white flour . . . . . . 79 . . . . . . . . . . 98 4 68 Bread, zwiebach . . . . . . . . . . . . . . . . 82 _ _ _ , _ . _ _ _ _ 98 1O 68 Bread, zwiebach with 15% pea- nut grits . . . . . . . ._ . . . . . . . . . . . 9() , , . . . . . . . . 98 4 68 Bread, graham and milk . . . . . . . . . 90 95 94 29 14, 22, 26 Bread, white and milk . . . . . . . . . . . 93 95 97 26 , 26 Bread and meat . . . . . . . . . . . . . . . . 92 90 98 3 , 17 Bread, cereal and milk . . . . . . . . . . . 93 95 98 25 11, 17, 19, Bread, milk, bananas . . . . . . . . . . . . 91 95 98 23 32 Bread, meat, milk, eggs, vegetables 93 95 98 30 2, 16, 20, Bread, meat, milk, vegetables. . . . 93 96 97 43 17, 20, 28, Bread, rice, meat, fish, vegetables. 81 . . . . . . . . . . 97 6 31 Bread, eggs, beans, potatoes . . . . . . 83 96 95 2 9 Broccoli (rats) . . . . . . . . . . . . . . . . . . 54 36 81 1 84 Buckwheat, meat extract, soybean sauce . . . . . . . . . . . . . . . . . . . . . . 75 43 97 2 31 Buckwheat flour (rats) . . . . . . . . . . . 83 86 95 2 84 Burdock root, edible . . . . . . . . . . . . . 25 . . . . . . . . . . 94 1 31 Cabbage . . . . . . . . . . . . . . . . . . . . . . . 46 64 82 3 77, 85 Cabbage, savoy . . . . . . . . . . . . . . . . 82 94 85 2 50, 71 Cabbage (rats) . . . . . . . . . . . . . . . .. 58 68 85 5 84 Cakes, aleurone . . . . . . . . . . . . . . . . 86 . . . . . . . . . . 96 8 68 Cakes, English Albert . . . . . . . . . . . 77 . . . . . . . . . . 98 4 68 Carrots . . . . . . . . . . . . . . . . . . . . . . . . 61 94 82 2 14, 71 Carrots (rats) . . . . . . . . . . . . . . . . .. 26 80 90 4 84 Carrots, soybean sauce . . . . . . . . .. 27 49 96 1 31 Celery (rats) . . . . . . . . . . . . . . . . . . . 67 67 85 2 84 Chard, Swiss (rats) . . . . . . . . . . . . . 71 6O 62 3 84 Cheese . . . . . . . . . . . . . . . . . . . . . . . . . 93 95 . . . . . . . . . . 1 9 Cheese, high rennet (at 32° F.) . . . 95 96 . . . . . . . . . . 3 46 Cheese, low rennet (at 32° F.). . . . 95 96 . . . . . . . . . . 4 46 Cheese, high rennet (at 40° F.) . . . 99 98 . . . . . . . . . . 6 46 Cheese, low rennet (at 40° F.). . . . 98 96 . . . . . . . . . . 7 46 Cheese, high rennet (at 60° F.) . . . 98 96 . . . . . . . . . . 3 46 Cheese, low rennet (at 60° F.). . . . 99 96 . . . . . . . . . . 3 46 Cheese, Camembert . . . . . . . . . . . . . 86 85 . . . . . . . . . . 2 46 ;....w2n.»_~_~ _..__....,..a...m COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 17 V ble 8. Average digestibility of human foods other than fats and oils, compiled—Continued Ether Carbo- Protein, extract, hydrates, Number References percent percent percent averaged Table 9 Cheese, cottage . . . . . . . . . . . . . . . . 94 95 97 4 10, 46 ‘llheese, green . . . . . . . . . . . . . . . . . . . 96 92 . . . . . . . . . . 2 46 _eese, old cold storage... .. . . . . . 94 92 . . . . . . . . . . 2 46 eese, Roquefort . . . . . . . . . . . . . . 94 91 . . . . . . . . . . 1 46 eese, skim milk . . . . . . . . . . . . . . . 97 89 . . . . . . . . . . 1 46 eese, Swiss . . . . . . . . . . . . . . . . . . 92 91 . . _ . . . . . . . . 1 46 estnut flour . . . . . . . . . . . . . . . . . . 56 63 98 2 8 ‘cken . . . . . . . . . . . . . . . . . . . . . . . 97 97 . . . . . . . . . . 4 5 ken loaf . . . . . . . . . . . . . . . . . . . 97 99 100 2 12 nut . . . . . . . . . . . . . . . . . . . . . . . 75 92 97 1 27 3" onut oil meal (rats) . . . . . . . . . . 64 97 72 2 84 - a . . . . . . . . . . . . . . . . . . . . . . . . . 7 64 . . . . . . . . . . 12 81 llards . . . . . . . . . . . . . . . . . . . . . . . 67 100 45 2 67 5 ards (rats) . . . . . . . . . . . . . . . . . 73 52 so 2 84 - n . . . . . . . . . . . . . . . . . . . . . . . . .. s5 . . . . . . . . .. 93 1 71_ m bread . . . . . . . . . . . . . . . . . . . . 60 . . . . . . . . . . 96 3 35 - , green . . . . . . . . . . . . . . . . . . .. 84 ' 41 97 1 7O "rn meal . . . . . . . . . . . . . . . . . . . . . 76 58 98 3 7, 13, 14 n meal (rats) . . . . . . . . . . . . . . . . 80 79 98 6 85 m meal soup . . . . . . . . . . . . _ . . . . 90 86 96 1 55 - meal and wheat flour soup. . . 90 86 96 2 55 rn meal porridge . . . . . . . . . . . . . . 76 85 95 1 55 \ meal, whlte, raw (m frozen pudding) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 3 45 meal, milk, apples, butter. . 77 . . . . . . . . . . 99 17 65 tonseed meal . _ . . . . . . . . . . . . . . 78 100 60 5 72 ers, a . . . . . . . . . . . . . . . . . . 91 100 99 10 25 hits, milk, butter . . . . . . . . . . . 95 97 97 10 25 ' » m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 . . . . . . . . . . 7 37 = . . . _ . . . . . . . . . . . . . . . . . . . . . 70 80 94 6 27 k meat . . . . . . . . . . . . . . . . . . . . . 91 98 . . . . . . . . . . 4 5 all . . . . . . . . . . . . . . . . . . . . . .. 94 95 . . . . . . . . . . 5 17g, 17, 37, , soft boiled . . . . . . . . . . . . . . . . 96 94 . . . . . . . . . . 1 79 a , . . . . . . . . . . . . . . . . . . . . . . 97 96 . . . . . . . . . . 1 79 gnaw)“ . . . . . . . . . . . . . . . . .. 91 39 _ . , _ , , _ _ ., 3 17 ard boiled . . . . . . . . . . . . . . . 97 99 _ _ . _ _ _ _ _ . _ 1 14 lk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 . . . . . . . . . . 6 37 H» ant (rats) . . . . . . . . . . . . . . . . 44 69 88 3 84 lant, soybean sauce . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 1 31 j. a . . . . . . . . . . . . . . . . . . . . . . . . . 73 . . . . . . . . . . 99 3 13 w- ~ (in frozen pudding) . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4 45 ~ ,_.s0ybean sauce . . . . . . . . . . . . . 20 . . . . . . . . . . 91 1 31 _ ta bread . . . . . . . . . . . . . . . . . . 51 . . . . . . . . . . 97 8 35 V ‘ta mush . . . . . . . . . . . . . . . . . . 48 . . . . . . . . . . 99 4 35 ’ . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 88 97 1 27 , butterfish . . . . . . . . . . . . . . . . . 92 86 . . . . . . . . . . 3 40 ’ 0d . . . . . . . . . . . . . . . . . . . . . . 96 97 . . . . . . . . . . 4 5 , dried . . . . . . . . . . . . . . . . . . . . . 99 90 . . . . . _ . . . . 1 31 ayfish . . . . . . . . . . . . . . . . . . . 93 94 . . . . . . . . . . 8 40> A addock . . . . . . . . . . . . . . . . . . 99 91 . . . . . . . . . . 1 14 y» , dried (Kusaya-aji) . . . . . . . . . 89 47 . . . . . . . . . . 1 31 j» mackerel . . . . . _ . . . . . . . . . . . . 93 95 . . . . . . . . . . 3 37 salmon . . . . . . . . . . . . . . . . . . .. 95 95 . . . . . . . . .. 4 5, 311 w , shellfish . . . . . . . . . . . . . . . . . _ 97 85 . . . . . . . . . . 1 31 , soybean sauce . . . . . . . . . . . . . 95 87 . . . . . . . . . . 3 31 V» , milk, cereal, bread . . . . . . . . . 94 97 98 7 20 Q1 ,_ raw graham (in frozen pud- mg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 3 45- ,_ raw patent (in frozen pud- ' m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 3 45- ~ - , wheat flour soup . . . . . . . . . . 91. 88 97 1 55 “ - , low grade flour soup . . . . . . . 91 86 96 1 55 -, concentrated army, German ' 1 1 ._ . . . . . . . . . . . . . . . . . . . . . 80 . . . . . . . . . . 97 4 68 , dned, soybean sauce . . . . . . 31 . . . . . . . . . . 89 2 31 ; . . . . . . . . . . . . . . . . . . . . . . . . 45 68 96 1 27 p1. uts . . . . . . . . . . . . . . . . . . . . . 72 . . . . . . . . . . 92 4 4, 7 fresh fat (roasted) . . . . . . . . . 99 99 . . . . . . . . . .1 4 33 ’ 75 . . . . . . . . . . . . . . . . . . . . 1 7 59 . . . . . . . . . . 98 7 35 ‘éaadtnaea:1111111111111: 18 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION Table 8. Average digestibility of human foods other than fats and oils, compiled—Continued _ Ether Carbo- Protein, extract, hydrates, Number References percent percent percent averaged Table 9 Kafir bread, soft . . . . . . . . . . . . . . . . 51 . . . . . . . . . . 96 7 35 Kafir mush . . . . . . . . . . . . . . . . . . . . . 48 . . . . . . . . . . 96 3 35 Kaoliang bread . . . . . . . . . . . . . . . . . 19 . . . . . . . . . . 96 9 35 Kaoliang mush . . . . . . . . . . . . . . . . . 12 , . . . . . . . . . 96 8 35 Lentils . . . . . . . . . . . . . . . . . . . . . . . . . 60 . . . . . . . . . . 84 1 44 Lettuce (rats) . . . . . . . . . . . ., . . . . . . 61 64 84 1 84 Lotus rhizone, soybean sauce. . . . . 63 . . . . . . . . . . 93 1 31 Macaroni . . . . . . . . . . . . . . . . . . . . . . 84 56 97 3 30 Macaroni, Calc . . . . . . . . . . . . . . . .. 91 100 67 6 30 Macaroni (rats) . . . . . ._ . . . . . . . . . . 94 85 99 2 84 Macaroni or vermicelli, beef ex- tract, soybean sauce . . . . . . .. 91 81 99 4 31 Meat . . . . . . . . . . . . . . . . . . . . . . . . . . 98 . . . . . . . . . . . . . . . . . . . . 1 71 Meat, raw . . . . . . . . . . . . . . . . . . . . . 93 81 . . . . . . . . . . 1 58 Milk . . . . . . . . . . . . . . . . . . . . . . . . . . 92 97 89 9 1, 17411, 17, Milk (calc.) . . . . . . . . . . . . . . . . . . . . 100 99 100 4 17, 60 Milo bread . . . . . . . . . . . . . . . . . . . . . 40 . . . . . . . . . . 96 8 35 Milo mush . . . . . . . . . . . . . . . . . . . . . 34 . . . . . . . . . . 98 4 35 Mushroom, soybean sauce... .. . . . 19 . . . . . . . . . . 81 1 31 Mustard greens (rats) . . . . . . . . . . . 70 68 69 2 84 Mutton leg (roasted) . . . . . . . . . . . 98 98 . . . . . . . . . . 4 33, 47 Nerka (breakfast food) . . . . . . . . . . 81 . . . . . . . . . . 98 1 13 Okra (rats) . . . . . . . . . . . . . . . . . . .. 39 45 82 4 84 Oatmeal or rolled oats . . . . . . . . . . . 83 83 97 l5 61, ‘lg, 22, Oatmeal bread (2/3 wheat, 1/3 oatmeal) . . . . . . . . . . . . . . . . . . . 88 94 99 1 74 Oatmeal, bread and butter . . . . . . 64 95 22 1 59 Olives . . . . . . . . . . . . . . . . . . . . . . . . . 65 78 91 3 27 Orange meat . . . . . . . . . . . . . . . . . . . 76 . . . . . . . . . . 95 1 13 Peanuts . . . . . . . . . . . . . . . . . . . . . . . . 89 88 92 1 27 Peanut butter . . . . . . . . . . . . . . . . . . 91 88 92 - 1 27 Pears . . . . . . ._ . . . . . . . . . . . . ; . . . . . . 78 90 97 2 27 Peas . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 73 96 5 10, 20 Peas, cooked in soft water... .. . . . 90 88 . . . . . . . . . . 1 60 Peas, cooked in hard water. .. . . . . 83 89 . . . . . . . . . . 1 60 Peas, dry . . . . . . . . . . . . . . . . . . . . . . 83 36 96 1 14 Peas, clay . . . . . . . . . . . . . . . . . . . . . 74 63 88 7 32 Peas, lady . . . . . . . . . . . . . . . . . . . . . 83 65 95 14 32 Peas, whipperwill . . . . . . . . . . . . . . . 70 69 87 12 32 Peas, blackeye, cooked (rats). . . . . 78 77 94 3 84 Pecans . . . . . . . . . . . . . . . . . . . . . . . . . 72 88 93 5 27 Persimmons . . . . . . . . . . . . . . . . . . . . 84 8O 92 1 27 Pork, roast . . . . . . . . . . . . . . . . . . . . . 99 96 . . . . . . . . . . 3 76 Potatoes, white . . . . . . . . . . . . . . . . . 75 80 98 1O 1?, 31, 71, Potatoes, white (rats) . . . . . . . . . . . 52 12 92 5 84 Potatoes, sweet, see sweet potato Prunes . . . . . . . . . . . . . . . . . . . . . . . . . 80 88 96 1 27 Pumpkin, soybean sauce . . . . . . . . . 89 67 99 1 31 Pumpkins, dried (rats) . . . . . . . . . . . 47 78 94 3 84 Rice . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 97 97 8 10, 31, 71 Rice, cooked (rats) . . . . . . . . . . . .. 84 71 99 2 84 Rice and meat extract . . . . . . . . . . . 80 93 99 1 14 Rice bread—2/3 wheat, 1/3 rice. . 90 96 99 1 74 Rice, barley, vegetables . . . . . . . . . . 74 97 97 2 31 Rice, meat extract, soybean sauce. 8O 45 99 3 31 Rice, barley, meat, fish, vegetables 7O . . . . . . . . . . 97 5 31 Rice bread . . . . . . . . . . . . . . . . . . . . . 69 90 93 74 50, 9;, 68, Rye bread, black . . . . . . . . . . . . . . . . 51 . . . . . . . . . . 92 31 68 Rye bran, coarse, in bread . . . . . . . 51 . . . . . . . . . . 83 2 69 Rye bran, in bread . . . . . . . . . . . . . . 62 . . . . . . . . . . 91 4 69 Spinach (rats) . . . . . . . . . . . . . . . . . . 72 v 30 73 3 84 Squash (rats) . . . . . . . . . . . . . . . . . . 44 50 75 2 84 Starch, raw corn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4 45 Starch, raw potato . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 4 45 Starch, raw rice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 2 45 Starch, raw wheat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 3 45 Starch, corn (rats) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 12 84 COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 19 f le 8. Average digestibility of human foods other than fats and oils, compiled—Continued _ Ether Carbo- Protem, extract, hydrates, Number References percent percent percent averaged Ta le 9 - _ w potatoes (rats) . . . . . . . . . .. 34 67 97 15 84 potatoes, soybean sauce .. . . 10 54 98 2 31 oas . . . . . . . . . . . . . . . . . . . . . . . . . . 85 . . . . . . . . . . 97 2 9 a omatoes, dried (rats) . . . . . . . . . . . 35 52 81 1 84 2; - w soybean sauce . . . . . . . . . . . . . 50 47 95 1 31 r nip greens (rats) . . . . . . . . . . . . . 64 72 74 2 84 ip roots (rats) . . . . . . . . . . . . . . 34 92 89 1 84 l . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 98 . . . . . . . . . . 3 63 , roasted . . . . . . . . . . . . . . . . . . . 99 98 . . . . . . . . . . 6 33 ll . . . . . . . . . . . . . . . . . . . . . . . . 77 85 94 9 27 eat germ . . . . . . . . . . . . . . . . . . . . 86 . . . . . . . . . . 98 1 13 eat, rolled, breakfast food .. . . . 79 . . . . . . . . . . 95 2 7’, 13 eat, shredded, breakfast food. . 58 . . . . . . . . . . . . . . . . . . . . 1 7 f ' eat, breakfast food . . . . . . . . . . . 72 . . . . . . . . . . 96 3 13 ' eat, breakfast food . . . . . . . . . . . 73 71 89 3 30 eat (rats) . . . . . . . . . . . . . . . . . .. 78 61 92 3 84 >~ eat bran, coarsely ground. . . . . 28 . . . . . . . . . . 56 8 43 ‘ eat bran, finely ground . . . . . . . 4:) . . . . . . . . . . » 57 8 43 eat bran (rats) . . . . . . . . . . . . . . 74 47 60 10 84 eat bran bread . . . . . . . . . . . . . . 44 . . . . . . . . . . 63 2 68 eat shredded, bacon, orange juice . . . . . . . . . . . . . . . . . . . . . . 80 97 . . . . . . . . . . '5 53 am, soybean sauce . . . . . . . . . . . . 60 48 97 1 31 ‘ east, dried brewers’ (rats) . . . . . . 80 0 96 12 84 averaged in Tables 7 and 8 8 Table 9. References to human digestion experimen ~. 1. Conn. Exp. Sta. (Storrs) Report 1896 42. U.S.D.A. Bulletin 687 i 2. Conn. Exp. Sta. (Storrs) Report 1897 43. U.S.D.A. Bulletin 751 3. Conn. Exp. Sta. (Storrs) Report 1901 44. U.S.D.A. Bulletin 781 4. Conn. Exp. Sta. (Storrs) Report 1905 45. U.S.D.A. Bulletin 1213 _ 5. Conn. Exp. Sta. (Storrs) Report 1905 46. U.S.D.A. Bur. Animal Industry C11‘. 166 6. Maine Exp. Sta. Report 1898 47. U.S.D.A. Farmer's Bull. 526 I 7. Maine Exp. Sta. Report 1905 Bul. 118 48. U.S.D.A. Farmer's Bull. 1207 8. Maine Exp. Sta. Bul. 108. 131 49. Exp- Sta- 11860111101662 t 5 9_ Minnesota Exp. Sta. Bul. 74 50. Exp. Sta. Record 11:375-376 ‘10. Minnesota Exp. Sta. Bul. 92 51. ExP- S1»?- 13900161114734) f. . Minnesota Exp. Sta. Bul. 111 ’ 52. Jour. Biol. Chem. 23 2505-11 .12. Texas Agr. Exp. Sta. Bul. 163 53. Jour. B101. Chem. 38:43-48 18, Ontario Agri. College, Canada, Bul. 162 54. Jour. B101. Chem. 23 :508 U.S.D.A. Ofiice Exp. Sta. Bul. 21 55. Exp. Sta. Record 10:180-181 U.S.D.A. Office Exp. Sta. Bul. 43 56. ExP- Sta- Reflord 111659-660 U.S.D.A. Office Exp. Sta. Bul. 44 57. ExP- 368-11-8001-‘6121274 U.S.D.A. Office Exp. Sta. Bul. 53 58- EXD- Sta. Record 14 :71 . U.S.D.A. Ofiice Exp. Sta. Bul. 84 59. ExP- Sta- ReCOId 14 31102 U.S.D.A. Ofiice Exp. Sta. Bul. 85 60. ExP- 3113-1180011115164 U.S.D.A. Otfice Exp. Sta. Bul. 89 61. Minnesota Exp. Sta. Bul. 54 ' . U.S.D.A. Ofiice Exp. Sta. Bul. 98 62. U.S.D.A. Bul. 1033 U.S.D.A. Ofiice Exp. Sta. Bul. 101 63. Jour. Ag- RQS- 61333-4 U.S.D.A. Office Exp. Sta. Bul. 107 64- Join‘. Biol. Chem. 571308-10 U.S.D.A. Ofiice Exp. Sta. Bul. 117 65- Jour- Home Econ- 17 z75-8 U.S.D.A. Office Exp. sm. Bul. 121 66- Revue general des. Sclences. 56=614 . U.S.D.A. Office Exp. Sta. Bul. 126 67. Landwirtschaftlich Versuchstationen. . ggce Exp. SSta. 79-80 :457-458 - -D- - c9 XP- ta- u - 68. Unter uchun uber d s oldate r t. . U.S.D.A. 011106 EXP. Sta. B111. 149 Berlins 1897 €28_172, g14§218 n B o U.S.D.A. Ofiice Exp. Sta. Bul. 156 69 sk d. . h A h. f Ph i1 . U.S.D.A. Office Exp. Sta. Bul. 159 ' 33 égavlsc e re 1v “r yswogle‘ . U.S.D.A. Office Exp. Sta. Bul. 187 ' '_ _ _ _’ _ . U.S.D.A. Office Exp. Sta. Bul. 193 70. Skandinavische Archiv fur Physlologle. U.S.D.A. Bulletin 310 231163-169 U-S-D-A- Bulletin 470 71. Skandinavische Archiv fur Physiologie. v U.S.D.A. Bulletin 505 273550-235 ' }’,;§-_g-_g-_ $111123?‘ '12. Zeitschriig: éur Unteasficglénfigler Nah- . U.S.D.A. Bulletin e30 rungs a“ Fmlssm‘ e - . U.S.D.A. Bulletin 649 73. Jour. of Hygiene 12 :132-133 U.S.D.A. Bulletin 681 74. Lancet Vol. 11 for 1917 :724-726 20 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION Table 9. References to human digestion experiments averaged in Tables 7 and 8—Continued 75. Report of Food Commission of the 80. Zeitschrift Untersuchung Nahrungs Royal Society 8-24 und Genussmittle. 7 :529-545 76. Zeitschrift fur Biologic N. S. 24 :377-406 81. Archive fur Hygiene. 60:175-190 77. American Journal of Physiology. 82. American Jour. of Diseases of Chil- 10:81-99 dren. 18:158-172 7,8. Archive fur Physiologie, 38 :614-616 83. U.S.D.A. Bul. 1033 79. Deutsche Medizinische Wochenschrift. 84. Texas Agr. Exp. Sta. Bul. 678 53 :2308-10 85. This bulletin The average digestibility of many of the fats and oils, Table 8, is over 95 percent and for most of them it is 96 percent or over. Fats having lower digestibilities are cow butter 93.1 percent, corn oil with other fat 93 percent, hard palate fat 93.7 percent, lard 95 percent, ox marrow fat 93.5 percent, nut butter fat 94.9 percent, and tea seed oiI 91.2 percent. The digestibility is less than 90 percent for beef fat, 88.9 percent, and mutton fat 80.5 percent. According to Cowgill (13), if the melting point of edible fats is such that they are liquefied in the alimentary tract, they are digested and absorbed to about the same extent; the dif- ferences are of no practical significance. The digestibility of the ether extracts listed for many foods in Table 8 is lower than that of the fats and oils cited in Table 7. This is probably due partly to the low percentages of ether extract in the foods in question, causing exaggerations of small errors as has been shown in digestion experiments with chickens (24) and with rats (27). The presence of metabolic fat may also have produced low apparent digestibility. The actual digestibility of fats and oils con- tained in foods is probably higher than is reported in Table 8. Some of the human digestion experiments were conducted with simple mixtures, but with other experiments complicated diets were used. As pointed out, with chickens (24) and with rats (27), digestibilities of in- dividual foods calculated from complicated diets are more variable than when simple mixtures are used. The average digestibilities of some of these mixtures are given in Table 8. Adequate numbers of human digestion experiments have been made with many foods, such as meats, fish, bread, fats and oils, and some cereals. For other foods, the number of experiments is not sufiicient; this in- cludes especially nuts, fruits, and many vegetables. As pointed out (27), digestion experiments with rats may be used as an aid in estimating the digestibility of some human foods. Table 8 contains also the average digestibilities of certain mixtures, which were taken to have some value in ascertaining the digestibility of human foods. The ‘average digestibilities of groups of foods from Table 8 are given in Table 12 together with other data which will be discussed on a sub- sequent page. The average digestibility of the mixed diet in Table 11 is that given by Atwater, by Sherman, and by others. Digestibility of Crude Fiber The number of human experiments in which the digestibility of crude fiber was determined is comparatively small. Jaifa (39) and Oshima (50) COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 21 report experiments in which the digestibility of crude fiber and nitrogen- free extract were determined in fruits, nuts and vegetables. Some of them are listed in Table 10. The digestibility of crude fiber in nuts, fruits and vegetables is fairly high, being about 75 percent. The digesti- bility of the crude fiber in entire wheat or rye bread is about 50 percent, while in wheat bran it may be appreciably lower. Table 10. Digestibility of crude fiber in some human foods and mixtures Percent Percent Apple sauce 95 Celery, cabbage, carrots 63 Beets 84 Celery, cabbage, carrots 47 Rye bran in bread 77 Bread, dry fruit, oil 44 Bread, wheat and rye 45 Bread, fruit, oil 63 Bread, white 53 Rice, barley, vegetables '76 Bread, whole wheat 45 Rice, vegetable, fish 82 Bread 44 Rice, vegetables, meal 91 Cabbage 77 Wheat and rye bread 37 Corn, green 59 Wheat and rye bread 50 Potatoes 74 Wheat and rye bread 30 Wheat bran, finely ground 70 Entire rye bread 55 Fruit and nuts, 16 exp. 75 Entire rye bread 44 Fruit and nuts, 11 exp. 82 Entire wheat bread 45 Fruit and nuts, 2 exp. 77 Rye bread 46 Fruit and nuts, 1 exp. 77 Rye bread 36 Potatoes, glutin, fat, beer 78 Wheat bread 53 Potatoes, fat, beer 79 Wheat bread 53 Metabolizable Energy Metabolizable energy is the energy of the food less the energy in the excrement, both fecal and urinary, and, in case of ruminants, the energy in gases produced by fermentation. Metabolizable energy includes all the energy of the food which might possibly be used by the animal. The calories of energy in human foods are, at the present time, ex- pressed approximately in terms of metabolizable energy (4, 8). Atwater, in 1895 (4), used Rubners factors for the fuel value of digestible nutrients for foods, namely 4.1 calories per gram of protein and of carbohydrates and 9.3 calories per gram of fat. These are the isodynamic values or food values of nutrients as calculated by Rubner and as discussed by Atwater (3) in 1887. These values at that time were considered to be tentative (4) and not to apply with exactness to the nutrients of all food materials, as they represented the results of only a small number of experiments made up to that time, nearly all with dogs. The metabolizable energies of digested fat or carbohydrates are practically the same as their heat of combustion. With protein, however, part of the energy is excreted in urea, so that the metabolizable energy is 4.1 calories per gram, com- pared with 5.7 calories per gram for heat of combustion of protein. The fuel values of the different foodimaterials averaged by Atwater and Bryant 1899 (6) were calculated by use of the factors of Rubner, which allow 4.1 calories for a gram of protein, the same for a gram of carbohydrates, and 9.3 calories per gram of fats. These amounts correspond to 18 calories of energy for each hundredth of a pound of protein and of carbohydrates and 44.2 calories for each hundredth of a pound of fat in the given food material. The assumption was made that the nutrients are completely digested, which is not correct. 22 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION Atwater and Bryant 1899 (5) after allowing for average digestibility, arrived at the values of 4.0 calories per gram for total protein and total carbohydrates and 8.9 calories per gram for total fats in a mixed diet of animal and vegetable origin. The protein of fruits and vegetables would have a lower value than other foods on account of the high percentages of non-proteids in the protein, 40 or 60 percent respectively being the values assumed. H. C. Sherman 1911 (53) and 1941 (54) used the values of 4 calories per gram of protein and carbohydrates and 9 calories for fats as repre- senting the approximate physiological fuel values of these constituents in all human foods, and these values are also used by Chatfield and Adams (12) and in Tables of Food Composition (11), and are discussed by Maynard (46). These values were derived by Sherman (54) from the following con- siderations: The metabolizable energy of digested protein was considered to be 4.35 calories per gram, of fats, 9.45 calories per gram, and of car- bohydrates 4.1 calories per gram. The app-roximate average digestibility of the nutrients in a mixed animal and vegetable diet were considered to be 98 percent for carbohydrates, 95 percent for fats and 92 percent for protein. The approximate physiological fuel values in an average mixed diet were then calculated to be: Protein 4.35 >< .92 = 4 calories per gram Fats 9.45 X .98 = 9 calories per gram Carbohydrates 4.1 X .98 = 4 calories per gram The average coeflicients of digestibility of classes of foods according to Atwater and Bryant (5) as based on the limited data then available, are given in Table 11. The approximate physiological fuel values for the constitutents, calculated for the classes of food by the method given above, are also given in Table 11. Table 11. Average coefficients of digestibility of foods in a mixed diet (Atwater) _ _ Physiological fuel Digestibility value, calories per gram Carbo- Carbo- Protein Fat hydrates Protein Fat hydrates Animal foods . . . . . . . . . . . . . . . . . . . . .97 .95 .98 4.2 9.0 4.0 Cereals and breadstufis . . . . . . . . . . . .85 .90 .98 3.7 8. 5 4.0 Dried legumes . . . . . . . . . . . . . . . . . . . .78 .90 .97 3.4 8.5 4.0 Vegetables . . . . . . . . . . . . . . . . . . . . . . . . 83 . 90 . 95 3. 6 8. 5 3.9 Fruits . . . . . . . . . . . . . . . . . ..~. . . . . . .. .85 .90 .90 3.7 8.5 3.7 Total food of average mixed diet . . . . . . . . . . . . . . . . . . . .. .92 .95 .98 4.0 9.0 4.0 The values given in Table 11 show that the calories of fuel value of food calculated by the average figures of 4-9-4 are too low for animal foods and too high for vegetable foods, as pointed out by Maynard (46). According to Fraps, Carlyle and Fudge (33), the metabolizable energy of foods for chickens on a maintenance basis can be calculated with an. excellent degree of accuracy from the digestible constitutents by means ..ut....i..... _...i.. .. 1m‘ .._ ..< . . COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 23 of the values of 4.4 calories per gram of digested protein, 4.2 calories per gram of digested nitrogen-free extract and of digested crude fiber, and 9.47 calories per gram of digested ether extract. These values for the digestible constitutents are nearly the same as those used for human foods by Sherman. Considering the fact that heat of combustion found was slightly lower than the calculated value for the chickens in case of corn meal, flour, kafir, rice bran, rice polish and starch (33), the value of 4.1 calories per gram for digested nitrogen-free extract and crude fiber, as used by Sherman and others, appears equally as desirable as the value of 4.2 calories used for chickens. Table 12 contains the average coefficients of digestibility of groups of human foods and the factors for calculating the metabolizable energy in calories per gram from the chemical composition, prepared with use of the values 4.35 calories per gram of digestible protein, 9.45 calories per gram of digestible fat and 4.1 calories per gram of digestible “car- bohydrates.” The metabolizable energy values of human foods are usually expressed in calories per pound; the factors for calculating directly to calories per pound from the percentage composition are also given in Table 12. Because no correction was made for non-proteid constitutents, the metabolizable energy factor for protein is too high for fruits and vegetables. Table 13 contains the average composition of the edible portion of a. number of human foods, from the compilation of Chatfield and Adams (12), together with the fuel value per pound as calculated by them, and the metabolizable energy as calculated from the factors given in Table 12. The productive energy is also given, which will be discussed on a subsequent page. The fuel value was calculated (12) by use of 4 calories per gram for protein and carbohydrates and 9 calories per gram of ether extract, as found by analysis. These are assumed to be the values for a mixed animal and vegetable ration, and they make no allowance for differences in digestibility between the different classes of foods. The metabolizable energy is secured by the use of the values in Table 12, and allows for differences in digestibility of the constituents o-f the various classes of foods listed. In the case of animal foods, the fuel value is lower than the metabo- lizable energy, for example, 990 "and 1010 respectively for roast chuck beef; 445 and 456 for’ fish. With nuts, the fuel values are too high; 2,900 calories for almonds, compared with 2,604 calories for metabolizable energy; 2,720 for roasted peanuts, compared with 2,440 calories for me- tabolizable energy. The fuel values are too high for fruits, such as 290 calories per pound for app-les compared with 279. calories metabolizable energy, and 230 calories for oranges compared with 216 calories of me- tabolizable energy. For beans the fuel value is 1,585 calories compared with 1,453 calories for metabolizable energy. For oat meal, the fuel value is 1,795 calories per pound and 1,663 for metabolizable energy. For fresh cabbage, the fuel value is 130 calories, while it is 104 calories 1111151334 . 1 N 0 I T A T S T N E M I R E P X E L A R U T L U C I R G A S A X E T 0, 8 6 0 N N r1 T E L L U B 24 0.: 0 00H 0.0 0 0.0 00 0 00 . . . . . . . .....................023? N02 0.00 0.0M 0.0 0.0 0.0 00 00 N0 . . . .35 oEw$0Q> v.5“ REEQ 0.822 N. . .2 m .00 0.02 0.0 0.0 0.0 m0 m0 R. .0201»? .5300 £32.60 .0:=moooo .0=5mwso J5: zuwpm fiwcocfiw .322 A|¢».-§-.? §.x §.§ 7.x ...- . - . . . - . - . - .-..---»@:=HQ .GQEE@m.~®Q @820 £25.20 avnfim $.00 .300 dwnmcan @200.“ diam 0.5 0.0.0 0.0 0.0 0.0 0.m 00 00 3 .. . . . . . . ......8.oo~ 3E3 6E . -0520 £520 00w dfirimo .302 39m 53 0.3 “s 0.0 0Q h; 0N. 8. 00 .fiv_o.owwiofimw_fi.www> we: 0.0m flimfi 0.0 0Q 5w 00 mm 00 . . . .956 0E5 .8532 .w0.8=oo .323 d manna £0303 d2nw~o0o> 0.02 0.0m 0.02 0.0 0.0 0.0 0N. 00 00 .....mao3w 3E3 622E wzsm 2222mm .2220 0532:: dw~aw~o0o> 0.5 0.0m 0.02 0.0 0.0 v.0 00 m0 0N. ......wmv@ Ea mimziwvfi. muEsmoq 2.02 N00 0.0 0.... . . . . . . . . . 0.N “.0 SC >0 6:5 wiax £20.45»; $8238.. c130 0.02 H00 v.0 0.0 0.0 0A hm 0N. v0 . . . . . . . . . . . . . . . . . . 15E 00.203 0.2 0mm ~60 0.0 0.0 T0 00 00 i. ..........gwzwbwtofi»... 32;? 0.02 0.00 0A; 0.6 0.“. 0.0 00 00 m.“ .... . . . . . . . . . . .1130?» awfificm 50~ 50w v.0 o... 0.0 0A n0 >0 .00 ...............Aw:.5wwozsanfivwaw mw.m.m ....... . . . . ..... .... . . . . . . . . . ..... . . . . . . . .. ....... ......UQ.~QU>POQMOUQQN—UCG.~W“MNMUW ...... . . . . . . . . . . . .......Q%.~ uwvflmvhm 0.: 0.5 0.02 0.0 0.0 0.0 00 m0 20 11.2.5020 Ewsmpw éfisa ifizm 0.00 0.00 0.2 0.0 T“. 0.0 00 ms >0 1.11.2000 65200.6 .333 €mofim §.§? kw-m @.£ .. . - - - ..-.. . - . - - - -..-.»H:QG Jmonkxosn Jmvsz» dub .135 two JGOMGQME SE50: .30: 902w £5.80 .500 Swims dHohwU . . . . . . . .. 0.3. . . . . . . . . .. 2.0 . 00 . . . . . . ........m=ouamm0mh 0.2 0.3» 00w v.0 0.0 0.0 00 >0 N0 .......................2o:3.x=2 0.02 0.00 0.00 04. 0.0 70 >0 00 m0 . . . . .................@wvosU 0.00 0.00 . . . . v.0 0.0 N0 m0 . . . . . - ..-¢ n '-..- 0.1 .P-€ ¢ -- . .¢.¢--.-.---¢--.-.-¢.¢--wmm . . ..-. . . . . . . . . .. -.... . .....@NU>@CNMTMQQ JMOHH5EJH~Nfl .203. £62012". down doomnlu-muwa $00233 02233 cmfiokm wofifiwza 000.500 533m $555.3 pombxo cmuwohm -0950 hwfim A550 $5M A550 023M 0:200 .60 muioiwo E30 .80 22.223 2596A 000.65. ofiwumonwflog Swhonv wimnsonwwwg 5500003000 Q0303» .233 Ens-E- mo 253M E >035. oisufloaafivi ufiuai-uwao .3“ 3:00am dH mznwa. 25 COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS owmN 0N3“ owow . . . . . . . . .. ooA .. . . . . NEW NmmA oNmA w. mam o o mHmN whA . . . . . . .@§::.E~.:=_._ szmoi bEwA 5R. 9.3 $2 m. “.3 o o Q: i: .. . . . . . . . . . afimzizta m2 £55 ......... .......... . . . . . . ..........................wQQNhw m. ........................Q@DH.~®@NHU $3 w? 5% mA NSN. o o mN odA . . . . . . éofifiomfioo EEAEE mam o-fl &.. o ... ...». - . . - . - . - . -...-.-..m ©% aw. N. .....................:5h% ALNA $2 £2 w. m4. ma» N. m2 mtm ..............EmAQ 2w ow i5 owpU .-..----.-.-<-.¢ $2 mBA $2 mA oNA NAN. 0N 5m Ad .............iwkww_ogs._wws ckcU E2 3B on: w. oNA odh w. AA ....» ................._.B_¢Q._8E.=h¢u mNm $9. 2% 8. Q? .2: w. NA 5m ....................oo3w pa...“ E00 Am m2 mNN ohA 9% o6 NA w. m6 . . . . . . ............m.w>mw_ MAZEBU ma: 32 on: oA m3 wAA N.m 5% Aim . . . . 1.33% =8: fiscoooU $2 ~52 £2 Em 9% h. A o mNm m.mN . . . .. . .. =moivE< QmExEU wmxéu 9a Now 8w o. A 93 o o wNA N.oN . . . . . . . . . . . . . . . . @5308 mwvézsu $5 ......................gw®h.w. MQQHHNU Am AA: 92 E. AiNm we oA N. AXA mmowfwmwnnmU NANA 2mm mNmm mN ma; A». o oAw w .. $3=m 2 o2 o2 A . A m3 N6 m. A N. m6 . . . . .. . . £53m 8&2“ dmvb .=S2:m m? $2 £2 m. mam oAR mA o.N 9w . . . . . . . . . ..E8@EE¢.» .353 “Aafim Q5 £2 5.2 o.N o. hm 0A3 o. A ...». o5 . . . QQ-mz, 5A3 35E Emifim A596 hwmA aAwN omAm Aim mh ad AN mbw AiAl . . . . . . . ..IT............mA:cWAnw~m 5 i: moN AAA w? 5w m. A. wA Hnarmzwzg i»: mxsm m2 :5 Q3 8. 9S o . . . . . . . . 05A m4: . .E3©vE AEJPA zawamsofi» unam AR. 22 c3 3. Q3 o . . . . . . . . . 92 i: .. . . .5335 x250 2wwwAoA3 ~25 one Nmm o3 ha. 06w c . oz: w.wA . . . . . . . . . . . . . . . . . . 135i an.“ . huswmx mivsmzh dwwmfios? 63w 3am fim 0AA; $2 we mNA. wsm w.” mA >3 . . . . . ............A€:..~E=H2i@m 8S £3 £2 we. mdA wan i" mA oNN . . . . . . . . . . . IABCA. noEEoo 28m mfl .................A.mv®hm.fifliw~wflfl0m Q: mm: 5: a. #3 mwh m. a. A Na ...... . . . . ... . .2»: 6223a swzwm mwN wNw m3 ww. wAR AiNN w. N. NA . . . . . .....................wmcmcwm ....-.. ...-........3.NH QPN%EQ@%VQE~:QUNQ w; .F| .-Q--v|~¢»- a - - » v2 AKN omN mN. Aéw mdA o. A Q. m. .... . . . . . . . . . . . . . . . ... Lint» 57:5. mNwA 38 oomN 9m >4. i: EN #3 wdA . . . . . . . ..8€~...3== BE. .2505? v5.0a 3Q wcsom .35 venom 5Q “awoken 208.3 £523 Acoohva i523 .2623 wviflwo moioiwo woioiwu :71» £35,? Jowbxo Con; Jomfixo imvwouh SE26 Smhucv 63E» ooh 3:50 posfim oZSoA-uohm ozmn: Awnh éumobm Z -2S@2 iweom £555: u: tan 03:3 0:» u: 993:0 25353.2» 1G6 mFAoflo o-nuuflonauoi 636v Aodu JEJQQOGEOU 6A 05am. ._ l. r...,..r\.L.BEL._F>FvE..xn-. r?!» . . . . 26 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT ‘STATION “0v .50“ 600.830‘ 0580a. . . . . . ... . . . . . . . Pwwfiflw 000“ 000“ 0>0“ 0.“ ““.““ 0.0> “.N v.“ v.0“ . . . . . . . . . . . . . . . . .000 05w $005,? N>v 000 000“ 0.0 v.> 0.>0 v.0 Nv 0.0“ . . . . . . . . . . . . “B00030 .005 000.“? wvw 000“ . . . . . . . . .. “v 0.0“ 0.>0 0.0 0.v 0.0“ . . . . . . . . . . . . . 10.35am >000 000““? “00“ v00“ 0v0“ v. 0.N“ 0.0> 0. 0.0“ . . . . . . . . . . . . . . 15030 .500 00055 “00“ v“0“ 0“0“ 0. 0.N“ 0.v> v. “.“ N.““ . . . . . . . . . . . . 1508.50 .500 000““? 0>0 0“0“ 000“ 0.“ 0. ““ 0.0> 0.“ 0N 0.0“ 1.50.“? 0550 .5555 ..50““ 505$ 0“0N 000N 00“0 >.“ 0.0 0.0“ “.N v.v0 0.0“ . . . . . ..............“w=w=m £5503 00 “N“ 00“ 0>.“ 0.00 N.v N.“ v. 0.N . . . . . . . . . . . . . . . .5000“ .000.“ 055.“. 00 0v“ 00“ 0>. 0.00 0.0 “.“ N. “.“ ...............““w0““ .300.“ 605.5,“. ©m §~-m q-m w. m. 0.? . ¢ - . . . . . . » . - . - _ - . 000 >00 000 >0.“ 0.00 0.0N 0.“ >. w.“ . . . . . . . . . . . . .5000 6000500 00030 ..... . . . . . . . . . . . . . . .. 000“ . . . . . . . . . . . . . . . . . . .. 0.00 . . . . . ... . . . . . . . . .. 0. . . . . . . . . . . . . . . . ..“.000“::0.~m .5000 Nm ~ o - q .m m . ? - w 1 . - ¢ - . _ . . . . - . . - - p - . - .?Q ©.N ®. m‘ m.N .- . ~ . . » . - . - - - . ~ - .-.»-:@mw-%|% 000 >0> 00> v.N v.>0 0 0 0.0 “.0N . . . . . . . . . . . . . . . . . . “.0580 505000 P.M Am.m. ........ . . . . . . . . . 13G.“ .0.~..“§2r “Unix mw Nw. o-w m-i N. N-? . . - . . - . . - - » . - . . n - . 0v> 00N“ 000“ “N 0.vN v.00 0. “ 0. 0 . N . . . . . . . . . . . . . . . . . . . . 100i“. .0005?“ w. ? . o»N . - . ~ - - . . . . . - . . ¢ - ¢ - u 0N““ 000“ 0>0“ 0 000 0 0 0N0 0 .v“ . . . . . . . . . . .50““005 .050 0.80m .0200 NvN“ 00>“ 0v>“ v.0 0 Nv 0. 0 0.00 0.0“ . . . . . . . .5585 400x050 .55“ .0200 00““ >00“ 0v0“ 0.. 000 0 0 0. “0 N0“ ....... . . 55505 500.0 .55“ Jion“ m w. N. q- .¢-¢.¢u » . - - - ~ . ‘IOIIIIQ-‘wflgnwwidm . . . . . . . . . . . . . . . . . . . . . . . . . ..WH“.QOQA% Nv0“ “>v“ 000“ 0~N 0MN“ 0.00 N. “ 0. “ 0.vN . 1213000 “.000 505050 .500. £00m“ . ...... . . . . . . . . . . . . . . . ..“.“®Uhm ~QNQQ . . . . . . . . . . . . . . . . . .. . . . . . . ...................%.“mv .mflwflm mm. fi-i q- h. . - - - - -.-.-.-v - - - - - -..-.un-.mafiw@m >0>“ 0“0N 000N v.0 >~“ 0.0“ 0.N 0.>v “.0N . . . . .........“0“5““ 055000 @ N ..-.-..... . . . . . ..@UHMNOH qmflwflwnmflQm w. i. m. .- -. . ~.-..-- .--.»:@®h% §fi. @- N. m. . - - - - - . . . - - - - . . ¢ . _vhlnnuluwowgmko . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .........M“.“MMOOO HO Ufliww 00““ 000“ 00>“ 0.“ 0.0 0.>0 N.“ v.> Nv“ . . . . . . . . . ..“.0v“0o05. S5 4005000 >v N0 0N“ “N.“ N.N0 N0 w. 0. 0N . . . . . . . . . . . . . . . 11500.00 “E3002 00“ 0“0 0“0 >. 0 >0 0.v 0 0.0 0.0 .... . . . . . . 1.20:3 .0000.“ .800 .0““““>“ fi @ Q. Aw . . . . . ...... . . . . . ........U““@HNmkNE v00“ 000“ 000“ >~ 0.““ 00> v. v.“ 0.0“ . . . . . . . . . “.3505: .50 45000003“ xm @. x. $.% . - . . . . . . . . . . . . . . . . ....§mmv.~% “UnviQQOA “x500 .80 “2500 .000 “Z500 .000 500.000 500000 500000 0.000000 .. 0:00.60 500000 020200 005200 020200 .004 .0053 £00050 .0000 .5550 .5395 $00000 $0.500 .055» . 00.0.“ 00.50 005m“ . 0013:0000 0305“ “0:»“ 5000.57“ 00302 “00::“»:0O|.u“50m Gui-z“ m0 0.50 o3“?- o-“u m0 .3023 0300:0000 “Eu 030:0 030515305 .035» “.50 .=..£8&.S0 .2 05s“. COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 27 for the metabolizable energy. Some values are nearly the same, such, as 385 and 383 for potatoes, 1,185 and 1,168 for white bread. The use of method of calculation which produces the fuel value tends to cause the differences in the energy values of different kinds of feeds to be less than they really are, while the use of the metabolizable energy tends to bring out the differences which really exist. The factors for metabolizable energy need to be made more accurate for vegetable foods, fruits and nuts especially, for which additional digestion experiments are needed and by more exact evaluation of the effect of the crude fiber and the non-proteids upon the energy values. Productive Energy Productive energy is measured by the energy stored up as fat and protein by a growing or fattening animal from that portion of the ration which exceeds the quantity used for all maintenance purposes. The pro- ductive energy of a mixed feed as measured by means of growing chickens was 67.9 percent of the calculated metabolizable energy fed in excess of maintenance requirements (31). This means that on an average 67.9 percent of the metabolizable energy fed in excess of maintenance was stored up in protein and fat. The‘ productive energy of corn meal, as measured by experiments with chickens, was 72 percent of the metabolizable energy, or 300 calories per gram of effective digestible nutrients (34). This means that the cost of utilization, including the work of digestion, the changes in energy consequent to the transformation of the nutrients to body protein and fat, and other changes consequent to the ingestion of the food, was 28 percent of the metabolizable energy of the corn meal fed, or 32 percent of the metabolizable energy of the mixed feed tested. Similar results were secured in experiments with rats (27). While growing chickens may possibly utilize a greater percentage of the metabolizable energy for purposes of maintenance than for storage in protein and fat, the work indicates that the utilization of the energy for maintenance is in proportion to the productive energy (25). Cost of utilization of a feed is the difference between the calories of metabolizable energy and the calories of productive energy of the food eaten. In case of productive energy, it consists of the energy consumed in digesting and utilizing the digested nutrients and in storing the pro- tein and fat in the animals. This is a complicated process and involves a number of chemical changes of various kinds. The cost of utilization of a given ration may depend upon the use made of the ration by the animal. When used for maintenance only, the cost of utilization may be less than when used for storage of pro- tein and fat. Likewise the cost of utilization may be different when the food is used for energy of work than when used for production of fat. The production of milk may result in a different cost of utilization from the production of fat and flesh or of work. The term net energy has been used to designate the energy value of a food for production of fat and flesh, for production of milk or of 28 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION other animal products or for energy. The term productive energy is limited to use of the ration for production of fiesh or fat on a growing animal, and therefore has a more definite meaning than the term net. energy. The productive energy values of 62 kinds of feed were measured in 192 tests on young growing chickens (25, 29, 30, 34, 35). Wide differences were found in the productive energy values of different kinds of feeds- and foods, but these differences were found to be due chiefly to differences in digestibility. The ability of the chickens to utilize the digested material from the different feeds, on the average, was reasonably uniform. The productive energy values per digestible unit of many different feeds were usually within 10 percent of that of corn meal. Similar results were found in experiments with rats (23). Very little data is available as to the productive energy of foods as measured by experiments on humans but this applies also to the fuel value or metabolizable energy, which was derived by Rubner from ex- periments with dogs. Energy Production Coefficients for Human Foods In the absence of experimental data for humans, the productive energy of human foods has been calculated from the data secured with experi- ments on chickens. Energy production coefficients for human foods have‘ been calculated by the same methods as used for calculating the energy production coeflicients for chicken feeds (28). In previous publicationson experimental work, the total energy, metabo- lizable energy, and productive energy, have been discussed in terms of calories per 100 grams. For many years, however, the energy values of human foods have been expressed in calories per pound of food (12, 48, 54) (metabolizable energy). In order to secure uniformity, the produc- tive energy of human foods will here be expressed in calories per pound of food. The productive energy of the feed or ration as measured by the ex- perimental work has been reported in several different ways in previous publications, namely, in calories per 100 grams of the feed, in calories per 100 grams of the effective organic constituents, in calories per 100' grams of the effective digestible nutrients, and in percentage of the metabolizable energy (23, 28). If thepcomposition of the food is known or assumed, the effective digestible nutrients can be calculated from the results of digestion experi- ments on it, or from average digestion coefficients as previously given. Using the most probable value ascertained by experiment for productive energy of the effective digestible nutrients (35), the productive energy can be calculated in calories per 100 grams. The calories per 100 grams can then be converted to calories per pound by multiplying by 4.54. This series of calculation can be made much shorter by using the energy production coefficients which combine the calculations named above and can be applied directly to the composition of the food, as has been done COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 29 for the metabolizable energy in Table 13, and on preceding pages. The productive energy coefficient for protein of a particular feed gives the calculated calories of productive energy which will be furnished by one pound of protein in that feed. Similar coefficients are given for ether extract or fat and nitrogen-fee extract. The crude fiber is not assigned any value in calculating the productive energy, and the nitrogen-free extract is used for the purpose of the calculation, not the so-called carbohydrates. Table 14 contains a calculation of the productive energy of average corn meal. The percentages in column 1 ‘are multiplied by the corresponding productive energy coefficients in column 2 to secure the product in column The total of the products in column 3 gives the productive energy of the average corn meal as calories per pound. Table 14. Calculating the productive energy of corn meal, whole grain Energy Percentage production Product of ingredient coefficient calories Ingredient (Table 13) (Table 15) per pound Col. Col. 2 Col. 3 Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 9.1 10.2 92.8 Ether extract or fat. . . .1 . . . . . . . . . . . . . . . . . . . . .. 3.7 22.3 82.5 Crude fiber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.0 0 ‘ 0 Nitrogen-free extract . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.9 13.1 941.9 Total, productive energy, calories pe.r pound of food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1,117.2 Energy production coefficients for groups of human foods are given in Table 15. The digestion coefficients are already given in Table 12 and are considered to be the most probable averages from the data in Tables 7 and 8. The productive energy values of the effective digestible nutrients, calories per gram as given in the Table 15, column 1, are the most prob- able values from the data in Bulletins 600, 625, 665, (24, 34, 35). The calories of productive energy (P.E.) per .01 pound for protein and nitrogen-free extract, column 2, are secured by multiplying the preceding column by 4.54. The calories of productive energy (P.E.) per .01 pound di- gestible fat, column 3, is the preceding column multiplied by 2.25; in the original work this ratio of fat to nitrogen-free extract was used. Columns 4 and 6 are secured from the respective coefficient of digestibility, Table 12, and the value in column 2. Column 5, for fat, is secured from the coefficient of digestibility of fat from Table 12 and the data in column 3. Table 15 contains the energy production coefficients for groups of foods, and in the present state of knowledge these averages seem suitable and convenient for use. Energy production coefficients could also be calculated for the individual foods, average digestion coefficients of which are given in Tables 7 and 8. This will be desirable when more detailed information has been secured regarding the digestibility and energy values of some of these human foods. 30 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION £53 525E uc 2:55 u: 35:05.2:- noflunucua mEfi-H .2 oSuH wk. mmw 1w. , m4 aw fi m. . . . . . . . . §wii~w>i “QNOQQ ~HQQGQQ “U? . . . . .:5¢.oo.:c “up . is m QM a 2 w n m? N i: "ZQN ..vw.z.m .wwir~mfc~wocmfimmvv..wwvmcw.%wo%waz . . . . . . up . a 6E i: .0 an IQ u * . . . . . . . . . . . . . . . 1.1.30“ . . . . . L3 .22: SB it? 622:8 . $2. l. Sm» H m o 2 w w m2. N mo w iiN w. . . . . . . . . 292.6% 92m .omnvfiw~wmo_ > . 5 o0 .0 . ll m: Néfi m.» mfiwm Q04 “QN . . . . . . . . . . ._w.@.m~ww~_%wwwwmm fiwmnmwwi~fl~wuNo> . . . . . 6 wmw$w.nouc@ mdcofi 25m: I 3 o> . . . . . . . . . . . . . . . . Gwfimwaw . . . . . . . . . . . . . . . . . . . . . .wOO.w.NH°m PN“ 0.2 ab“ $9M fix...“ comm . . . . . . . . . . . . . . Iwawon wan 23m Jvoiw mofismoq we ...@..~.ufl. .. .€». ...é...m.. QM. w 3m . . . . . . . .....§E qfix ficsalma=fimc¢w 52o . . w Q . . . . . ... . . . . . . . . . . . . . . . . . . . . ..A®wOHO5 v hflw5@ Nbfl o.oN 3m 95m FNA wmN . . . . . . . . . . . . . . . Imfiosw 22w 235$ . . . . . . . . . . . . . . . . ..H~Nh@ . . . . . . . . . . . . . . . . . . . . Imfnu .©wwum~ . . . . . . . . . . . . . . . . . . . . . . Qsou . . . . . Emawum 55a flaws? 23.5 5mm 3 3S . mo“ mAN T: aim ENA w _N . . . . . . . . . . . . . . . . . . 95cc dkoxuwflko 351%, fimokfi N a 0N m a 8w N EN fi w N . . Qnoc ozkmdswow fiwunzrxosn . . . . . . . . oaE dad: o up dais In no.8 2E. .. SN ..~.2. .. s? $2. .. i .... i352 x552 .50 “Qamlwwwwsw . . . . . . . . . . . . . . . . . . . . . . . . . . ..wZO Vim mwflrxm . . . . . . . . . . . . . . . . . ........ . . . . . . .. . . . . . . @153 x12 M. Nw w QN MNH Owwfi whflfi w.N . . . . . . . . . . . . . . . . . . . . . . . . . . Zzvwvoimv . . . . . . . . . . . . . . ...... . . . . . . . . . . . . . ........~Vw~fv% .. . . . . . . .. N. . . . . . . . . . . . . . . . ......................... @ w ... . . . . ..~............. . . . . . . . . . ..~NQ> nx-fiog m .535: Ema 915w dcuxomno Qwon doowmlfiwoz Qowbxu 3b Km amzfim “an c635 -5352 82w 5Q .13 ficvwis: minimum? wnson 3Q ficfibsc wfiflébo mo Q NH Bcomoaooo Hm um ‘finflwummu vcson s. 3Q wofioio Am i . § i111 COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 31 Productive Energy Values of Some Human Foods The productive energy values of a number of human foods are given in Table 13, where they can be compared with the metabolizable energy, and the fuel energy. The average chemical composition and the fuel energy, calculated to calories per pound, were taken from the compilation previously discussed (12). The productive energy is not always in proportion to the metabolizable energy. As can be seen from the factors in Table 13 (column 5), meat, eggs, certain cereals, and legumes have the highest proportionate values. Cheese, milk, certain cereals, white bread, white potatoes, sugar and a few vegetables have about one-fifteenth lower proportionate values. Next are entire wheat bread, rye bread, wheat bran, sweet potatoes, which have about one-tenth lower proportionate values. Fats and oils and most vegetables have about 20 percent proportionately lower value, while dried yeast is lowest. This discussion refers to the value of the productive energy in proportion to the metabolizable energy, and not to the relative productive energy value per pound of food. ' It is obvious that a diet calculated on the basis of productive energy would be somewhat different from a diet calculated on the basis of the metabolizable energy. l The relative energy values of the human foods are probably given more accurately by the productive energy than by the metabolizable energy, and more accurately by the metabolizable energy, as here calcu- lated, than by the fuel value as ordinarily calculated. Productive Energy of Wheat Flour The flour secured in the usual process of milling wheat is used as human food, while the by-products are usually used as animal food. Some authorities on food recommend the use of entire wheat fiour or Graham flour as human food. In times of scarcity of food, as during and after World War I and World War II, governmental action sometimes re- quires the production of more flour than usual per bushel of wheat by reducing the quantity of by-products. Whole Wheat fiour may deteriorate more rapidly than patent fiour, and may be more subject to insect damage. Average analyses (12) show that whole Wheat fiour is higher than patent fiour in protein, fat, calcium, phosphorus, iron and the vitaminslthiamin, riboflavin, and niacin. Whole wheat fiour is also claimed (12, 54) to have a slightly higher value for food energy than patent flour, but this statement is not in accordance with the values given in this publication, Table 13. The relative proportions of the different kinds of fiour and feed pro- duced from wheat depend upon the kind of wheat used, other charac- teristics of the wheat, and the variations in the process of milling made in the attempt to best meet the demands of the trade. According to correspondence with various millers doing business in Texas, ordinarily 32 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION wheat produces about '70 percent flour and 30 percent wheat bran and wheat gray shorts. The by-products may range from 6O percent bran and 40 percent wheat gray shorts to 40 percent bran and 60 percent shorts. A discussion of the terminology employed in describing flours has been presented by Snyder (55). Accompanying Snyder’s contribution is a report of a committee representing the Millers National Federation in which a system of nomenclature and definitions for flour is suggested. The committee considers that there are no chemical or physical constants that can be used to establish flour standards and definitions, because of the great differences in the composition of wheats and corresponding differences in composition- that occurs when flours are milled from dif- ferent wheats by the various systems of milling. Wheat of the same characteristics may produce flour of varying chem- ical composition from day to day in the same mill. The following definitions for the different grades were suggested: Flour is finely ground bolted wheat meal. Straight flour (or 100 percent flour) is all the bolted Wheat meal recovered from the wheat after removal of feeds, usually after about 5 percent low grade flour is taken off. Patent flour is the more refined portion of the wheat meal from which all or a portion of the clears have been removed. The patent flour may comprise from 60 to 95 percent of the total flour. Clear flour is the less refined bolted portion of the wheat meal recovered in the manufacture of patent flour. Millers according to their processing or trade demands divide this into first and second clears. First clear is the better portion of the clear when separated into two parts. Second clear is the remaining portion of the clear when first clear is removed. Patent flour usually contains lower percentages of protein and ash than the straight flour, and this, in turn, lower percentages than the clear flour. The approximate energy value of Graham, or entire wheat fiour, may be calculated from the percentages of straight flour, wheat bran and wheat gray shorts ordinarily produced from the wheat. For the pur- poses of this calculation, the wheat is assumed to produce 70 percent straight flour, 15 p-ercent gray shorts and 15 percent wheat bran. The production energy calculations are made in Table 16. The calculated metabolizable energy of the entire wheat flour, Table 16, is 1,475 calories per pound compared with 1,614 calories for the straight flour, and the productive energy is 941 calories compared with 1,061 for the straight flour. The values of the entire wheat flour cal- culated from the values of the straight flour, wheat bran and wheat shorts are close to those calculated from the energy production coeificients, Table 13. nm-wn-v: - COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 33 Table 16. Calculation o1‘ energy value of entire wheat flour, calories per pound Metab0liz- Productive Entire Metaboliz- able energy Productive energy Wheat products flour able energy constituents energy - constituents percent calories calories calories calories Flour, straight . . . . . . . . . 70 1614 1130 1061 743 Wheat bran . . . . . . . . . . . . 15 965 145 472 71 Wheat gray shorts. . .. . . 15 1336 200 848 127 Total, entire wheat flour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1475 . . . . . . . . . . . . 941 The metabolizable energy calculated by means of the coefiicient is 1,516 compared with 1,475 for Graham fiour and the productive energy is 970 compared with 941 (Table 16) for Graham flour. The energy value per pound is appreciably lower in the entire wheat flour than in the patent or straight flour. Productive Energy of Fats and Oils In the comparison of the productive energy values of various feeds, cottonseed oil was substituted for corn meal. In the average of 6 ex- periments with young growing chickens, 57 percent of the metabolizable energy of cottonseed oil in excess of maintenance was stored, compared with 72 percent for corn meal (35). With the eifective digestible nutrients of corn as 100 percent, cottonseed oil averaged 79 percent with at standard error of about 6.7 percent. In this work, instead of oil having 2.25 times the energy value of nitrogen-free extract, its energy value was about 1.8 times such value. The heat of utilization of oil was 43 percent of the metabolizable energy, compared with 28 percent for corn (35). The same energy values were found in six experiments with rats, namely 57 percent of the metabolizable energy was stored from oil compared with 72 percent from corn meal, and the effective digestible nutrients had 79 percent of the productive energy value of the effective digestible nutrients of corn meal. According to Forbes et al. (17) diets containing 2, 5, 10, and 30 per- cent fat compounded and fed to growing rats so as to supply each rat the same quantities of gross energy, protein and vitamins, produced gains in live weight, digestibility of nitrogen and the retention of nitrogen _ in the order of the increasing fat content of the diets; the superiority of the 5 percent over the 2 percent fat diet with respect to the utilization of both protein and energy being much greater than the superiority of the 30 percent compared with the 5 percent diet. Examination of the data of the single experiment shows that the average gains in weight of the 5, 10 and 3O percent fat diet of 231, 235, and 239 grams are probably within the limit of error, and likewise the energy retained of 440, 456, and 460 calories are probably within the limit of error. Re- petitions of this experiment are necessary to ascertain if there are really any differences in the energy value of the fat fed at these three levels. 34 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION From the results of a similar experiment with mature rats, in which voluntary activity during the respiration tests was excluded by subjecting the rats to a bright light, Forbes et al. (18) concluded that the heat production and the heat increments at maintenance and at supermain- tenance diminished in the order of the increasing fat contents of the diets and that the heat increments of the dietary supplements containing 2, 5, 10 and 30 percent of fat respectively were equivalent to 36, 31, 29 and 20 percent respectively of their gross energy. Examination of the data shows that the difierences in the heat production of the rats. on 2, 5, and 10 percent fat diets may have been Within the limit of error" of the work. Calculation of the productive energy of the diets containing- 2, 5, 10 and 30 percent fat gave 60, 65, 68 and 77 percent of the metab- olizable energy. The productive energy of the first two diets was lower than usual, so that the appreciably high results for lard is in part due to the low productive energy of the basal diet. As Forbes et al. reported - only one experiment, additional experiments seem to be needed to con- firm the conclusions drawn. Forbes et al. state (18) that the results represent growing animals during voluntary activity and mature animals at rest on diets com- paratively low in fat content, by virtue of which they are not in conflict with numerous published findings that work is performed more efficiently at the expense of carbohydrates than of fat. The productive energy value of lard has been reported by Forbes et al. (23) to be 6.59, 6.00, 6.28, 6.12 and (16) 7.57 calories per gram compared with the average of 5.10 for cottonseed oil with rats and 4.67 for chickens, by Fraps (23). The causes of these differences need to be ascertained- whether lard has a higher productive energy than cottonseed oil, or to what these differences are due. According to Wald and Jackson (59) rats on a normal diet ran an average of 2,000 revolutions on the running wheel daily, but when deprived of food or ‘water, their activity increased to 10,000 revolutions of the wheel daily. Increased activity occurred when the rats were deprived of thiamin or riboflavin, but not when they were deprived of vitamin A or of certain minerals. Deficiency in food nutrients may result in increases of activity. The additional running would increase the maintenance requirements of the rats, or decrease the apparent productive energy of the food, if al- lowance is not made for the increased activity. ' It should be pointed out that in Table 15, the productive energy co- efficients for all foods except fats and oils were calculated with the use of the factor 2.25 times carbohydrates for fat and oils. This factor was used in calculating the effective digestible nutrients in all work, and was not changed in calculating the productive energy coefiicients for the various foods, which were derived from experiments on the entire food. Acco-rding to Borsook and Winegarden (7, 9), if the conversion of fat to glucose occurs it involves an energy loss of about 21 percent, and the difference between the efficiency of fat and glucose utilization for work _.. '_4.A.\nQ.._!7u4x4-4 _ . .....<.. ._....<4-._..... .. .».\pAL....1.4..-.._ .. M» a 1'. -,._-.- ~ w‘ v. "rl"1~"vvwv _ flgwwg‘ “w. COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 35 is 11 percent. Keys (43) states that fat is about 16 percent less efiicient than carbohydrates for production of muscular work. Fat may be more of a heating food than either carbohydrates or protein. ' Substitution of cottonseed oil for part of the corn meal in a standard ration produced chicks with a much higher fat content and a lower live weight than those grown on the standard ration alone (21). The fat reduced the growth but increased the fatness of the chickens, and in this respect had a specific action. Sustitution of casein or other protein feed for corn meal produced chickens with a lower fat content than those- produced by the corn meal ration. While substitution of fat for corn meal increased the fat content of rats slightly (27) it did not have nearly as much effect upon rats as on chickens, and had little effect on the- gain in weight. Energy Cost of Utilization of Food Nutrients The organic nutrients ingested by animals undergo a long and com-- plex series of chemical changes before they are entirely utilized and the final products are ejected. Some of these changes contribute to the metabolic process and are necessary for life but others result in the» production of heat which, while useful under some conditions, ordinarily has no value. These latter changes are included in the energy cost of‘ utilization. . Approximately 70 percent of the metabolizable energy of food fed. in excess of maintenance may be stored as fat and protein in growing chickens and 30 percent may be liberated as heat as the cost of such. utilization. The cost of utilization may include (47) the energy of chewing and transporting the food through the intestines, the energy consumed in. the production of digestive enzymes, heat of bacterial action, especially in the digestive tract of ruminants, chemical changes of the» material. during digestion, energy of intermediate metabolism, stimulation of me- tabolism and chemical changes consequent on the storage of protein. and fat. The proteids, during digestion, may be split into about 21 amino acids 7-(56), which are absorbed and partly converted to body proteids. Young growing chickens may store 57 percent of the digested protein or 57 per- cent of the protein consumed in, excess of maintenance (31). Amino acids appear in the blood, are absorbed by the tissues, transformed. into other amino acids (52) by transanimation or transmethylation, or deaminized, so as to produce urea and glucose. The oxidation of ammonia to urea releases about 4 calories per gram of nitrogen; the energy cost of excretion of urea and other end products by the kidneys. involves a loss of perhaps 1 to 2 calories per gram of nitrogen (9). Trans- formations of some amino acids are exothemic, others endothermic and involve loss of energy (9). 36 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION Years ago, Rubner (4, 5) found that if a dog deprived of food required 100 calories per day for maintenance, the requirement would be 140 calories if fed meat, 115 calories if fed fat and 106 calories if fed cane sugar. The extra calories are considered as due to the specific dynamic action of the food (44, .45). If a maintenance ration is fed at intervals of two hours, the heat production does not rise appreciably above the basal metabolism level (9) and a small breakfast also exerts no specific dynamic action. The specific dynamic action does not represent the heat of utilization of the food, but the difference between the heat of utilization of the food and of the body nutrients which would have- been used if the food were not given (9, 18). Digestive processes cause the hydrolysis of fats into glycerol and fatty acids. The split products are readily absorbed and converted into :fat in the passage through the intestinal Walls (10). According to Frazer -(36) unhydrolyzed or partly hydrolyzed fat may be absorbed. Fats undergo other changes. Stearic acid may be changed to palmitic acid, or the re- verse may occur, unsaturated fatty "acids may be saturated, or the reverse. A portion of the fats are desaturated and built into the phosphatide molecule. Portions are also stored. Fats may also be formed from sugars, which involves loss of energy (18). Starches are converted by digestive enzymes first into maltose, then the maltose is hydrolyzed to glucose. Sugars such as sucrose, and milk sugar are hydrolyzed to the simpler sugars glucose, fructose and galac- tose. Part of the glucose in the blood stream may be stored in the liver as glycogen and part may be converted to fats. The carbon of bicarbonates may be incorporated to the extent of about 12 percent into the glycogen, so that the reaction is not simply condensation of glucose with elimination of water (52). Glucose undergoes intermediate changes, such as phos- phorylation, on the path to storage or complete oxidation, which involve loss of energy. Kertesz (42) reports that pectins are not digested by the saliva or secretions of the stomach or intestines but are rapidly decomposed when in- cubated with human feces, and probably not assimilated. Experiments with isotopic elements have shown that the body con- stituents are involved in continuous chemical processes and that there exists a close interaction between the food materials and body components. Protein, ester and other linkages op-en and close continuously. The amino acids, fatty acids and other units temporarily liberated mix with others from diet or tissue sources and become indistinguishable in origin. While in the free state the organic units take part in a variety of re- actions (52). The cost of the utilization of digested nutrients by humans for the storage of protein and fat is probably not far from the cost of the util- ization of digested nutrients by chickens for the storage of protein and fat. However, only a small percentage of the energy of the food is used by humans for production of protein and fat, even during periods of ‘rapid growth. The value of the food energy for maintenance or work by COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 37 humans may be in proportion to the productive energy, and the produc- tive energy may be a better measure of the relative net energy value of the food than the metabolizable energy; further investigation is needed. The percentage of metabolizable energy retained by humans in the form of protein and fat under normal conditions is quite small. According to Brody, page 566 (9), boys average 21.2 pounds in weight at the age. of 1 year -and 26.5 pounds at the age of two years, thus making a gain of 5.3 pounds in a year. If the gain is assumedto contain 2.2 calories a. gram (23) or 1,000 calories a pound, the total gain would be 5,300 calories a year, equal to 14.5 calories a day. If the consumption of food is as- sumed to be 1,200 calories of metabolizable energy equal to 840 calories of pro-ductive energy a day, Table 17, the gain in weight would be 1.2 percent of the calories of metabolizable energy or 1.7 percent of the produc- tive energy. Therefore, a very small proportion of the energy consumed is stored up as gain in a growing child. At the period of greatest gain, a boy 14 years old averages 103.1 pounds and at 15, 116.7 pounds, with a gain of 13.6 pounds a year equal to 37.3 calories per day. The daily allowance, Table 17, is 3,200 calories of metabolizable energy or 2,200 calories of productive energy. The energy in the gain in weight would. be 1.2 percent of the calories of metabolizable energy or 1.7 percent of the calories of productive energy. A fully grown person normally retains even smaller percentages of the energy of the food consumed. Almost all of the food is used for maintenance, or for the energy of work. Young growing chickens may store an average of 57.9 percent of the productive energy of a corn meal ration, and young rats may store 32.4 percent, Table 11, Bulletin 632 (23). Magnus-Levy, as cited by Sherman (54), estimated the minimum me- tabolizable energy of a fasting man of average size kept motionless to be 1,625 calories per day, and food suflicient for maintenance under the same condition would increase this by 175 calories. The heat of utilization of the food in excess of the heat of utilization of body tissue would thus be 175 divided by 1,800, or nearly 10 percent. Lusk, as stated by Sherman (54), estimated that an average-sized man with absolute- rest in bed without food would require 1,680 calories, and under the s-ame conditions with food would require 1,840 calories. The heat of utilization _ of the food in excess of that of the body tissue would then be 160- divided by 1,840, or 8.7 percent. These data do not measure the heat of utilization of the food ingested, but measure the difference between the heat of utilization of the food ingested and the heat of utilization of the body nutrients which would otherwise be oxidized. Daily Allowances for Calories of Metabolizable Energy and of Productive Energy The daily allowance of calories (presumably of metabolizable energy) are recommended by the Food and Nutrition Board of the National Re- search Council (15, 57) and these allowances are similar to those pre- 38 BULLETIN N0. 680, TEXAS AGRICULTURAL EXPERIMENT STATION Table 17. Assumed daily allowances of metabolizable energy and productive energy (70 percent) Metabolizable Productive energy, energy, calories calories Men (70 kg) Sedentar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2500 1700 Moderately active . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3000 2100 Very active . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4500 3100 Women (56 kg) Sedentary . . . . . . . . . . . . . . . . . . _ . . . . . . . . . . . . . . . . . . . . . . 2100 1500 Moderately active‘ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2500 1700 Very active . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3000 2100 Pregnancy (latter half) . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2500 1700 Lactation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3000 2100 Children up to 12 years Under 1 year (per kg) . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 100 7O 1-3 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1200 800 4-6 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1600 1100 7-9 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2000 1400 10-12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2500 1700 Girls 13-15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2800 1900 16-20 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2400 1700 Boys 13-15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3200 2200 16-20 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3800 2700 viously published. The productive energy, Table 17, was calculated on the assumption that 70 percent of the metabolizable energy of the mixed diet was productive energy. This is a little lower than the percentage of metabolizable energy of corn meal, and a little higher than the per- -centage of metabo-lizable energy of the feed mixtures used by the chickens. Human foods contain less crude fiber than those used for chickens. The figures, as rounded off, are given in Table 17. Use of productive energy in place of metabolizable energy will change the . relative energy values of most foods to a comparatively small extent. Whether or not 'it should replace the present system remains for the future to decide. The present system can be improved and made more accurate. ACKNOWLEDGMENT The author gratefully acknowledges the assistance of E. C. Carlyle and other members of the staff. SUMMARY The average composition of a number of human foods analyzed are given. Many vegetable foods on the dried basis contain 7 to 15 percent crude fiber, and others contain 20 to 42 percent protein. Human digestion experiments are given on oat meal, collards, cabbage, and string beans. The average digestibility of human foods, as compiled by the data in the literature, are given, with references. <~a,r.ia,..rnaa_-.a. .~.clnm_.e..lu.au <¢\_1 l COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 39 The fuel values in calories of human foods,ias given in the literature, are based on average values for the digestibility of a mixed diet of animal and vegetable origin, and are too low for many animal foods, too high for many vegetable foods, and do not show differences between some foods due to differences in digestibility. Factors for calculating metabolizable energy are given, which take into consideration differences in digestibility of various groups of food. On account of the deficiency of adequate data, these factors do not correct a for non-proteid nitrogen, and for crude fiber found in vertain vegetable-s. The composition and fuel values of a number of human foods are given as compiled by Chatfield and Adams, with the metabolizable energy and the productive energy as calculated from the data presented in this bulletin. As illustrative data, the fuel value is 990 calories per pound of roast chuck beef, compared with 1,010 calories of metabolizable energy; 2,900 calories fuel value for almonds, 2,604 calories metabolizable energy; 2,720 calories fuel value for roasted peanuts, 2,440 calories of metabolizable energy; 1,585 calories fuel value for beans, 1,453 calories of metabolizable energy; 130 calories fuel value for fresh cabbage, 104 calories metaboliz- able energy. The productive energy is measured by the energy stored up as fat it and protein by growing chickens from that portion of the ration which L exceeds the quantity used for all maintenance purposes, and as given in previous publications for various foods. Cost of utilization for productive energy is the difference between the calories of metabolizable energy and calories of productive energy in a i unit of a food and is about 30 percent of the metabolizable energy of a i i ' . human foods. i é ration by growing chickens. Production coefiicients are given for groups of foods, which can be “used for calculating the productive energy values of human foods. The computed productive energy values are given for a number of a ' aim The productive energy values are not always in proportion to the . metabolizable energy values. Meat, eggs, certain cereals and legumes have the highest proportionate values; cheese, milk, certain cereals, white i bread, white potatoes and sugar have slightly lower proportionate values. ~ Next comes entire wheat bread, rye bread, wheat bran and sweet po- a tatoes. Fats and oils have about 20 percent lower proportionate values. The relative energy values of human foods are probably given more nearly accurately by the productive energy values than by the metabo- . lizable energy values. The metabolizable energy and productive energy a values of entire wheat flour, or bread from it, are lower than the cor- c. responding values for white flour, whether calculated from the coefficients, _ or from the energy value of the bran, gray shorts and flour which a can be produced from the entire wheat. Daily allowances for productive energy in the human diet are calculated from the allowances recommended for metabolizable energy, on the as- 40 BULLETIN NO. 680, TEXAS AGRICULTURAL EXPERIMENT STATION sumption that the productive energy is 70 percent of the metabolizable energy. Previous work has shown that fats and oils have a productive energy of 1.8 times that of carbohydrates, instead of 2.25 times that they are usually supposed to have. Fats and oils therefore, appear to be more heating foods than carbohydrates but this matter requires further study. The storage of protein and fats by humans, the energy cost of utili- zation of human foods by humans, losses in energy consequent on the ingestion of human food, and transformation of nutrients in the body are briefly discussed. REFERENCES 1. Armsby, H. P. 1917. The nutrition of farm animals. The Macmillan Company, New York City. i 2. Association of Oflicial Agricultural Chemists. 1940. Methods of Analysis. 3. Atwater, W. O. 1887. Century Magazine. July 1887. Atwater, W. O. 1895. Methods and results of investigations of the chemistry and economy of foods. U. S. Department Agriculture, Oflice Exp. Sta. Bul. 21. Atwater, W. O. and Bryant, A. P. 1899. Report Storrs (Conn.) Agr. Exp. Sta. 1899 73. Atwater, W. O. and Bryant, A. P. 1899. The chemical composition of American food materials. U. S. Department Agriculture Office, Exp. Sta. Bul. 28 (revised). Borsook, H. and Winegarden, H. M. 1930. The free energy of glucose and tripalmitin. Proc. Nat. Acad. Sci. 16:559. Bridges, M. A. 1935. Food and Beverage analyses. Lea and Febiger, Philadelphia, Pa. Brody, Samuel. 1945. Bioenergetics and growth. Reinhold Publishing Corporation, New York City. 10. Bloor, W. R. 1943. Biochemistry of the fatty acids and their compounds the lipids. Reinhold Publishing Corporation, New York. ll. Bureau of Human Nutrition and Home Economics U. S. Department of Agriculture in cooperation with National Research Council. 1945. Tables of food composition in germs of eleven nutrients. U. S. Department of Agriculture Miscellaneous Publication o. 572. 12. Chatfield, C., Adams, G. 1940. Proximate composition of American food materials. U. S. Department of Agriculture Circular 549. 13. Cowgill, G. R. 1945. Relative nutritive values of animal and vegetable fats. Physio]. Rev. 25:664-686. 14. Du Bois, E. F. 1927. Basal Metabolism in Health and Disease. Lea and Febiger, Phila- delphia, Pa. 15. Food and Nutrition Board, National Research Council. 1943. Recommended dietary allowances. Reprint and Circular Series. National Research Council, Circuler 115. 16. Forbes, E. B. and Smith, R. W. 1944. Associative dynamic effects of protein, carbo- hydrates and fat. J. Nutrition 27:453-468. 17. Forbes, E. B., Swift, R. W., Eliott, R. F., and James, W. H. 1946. Relation of fat to economy of food utilization. I. by the growing albino rat. J. Nutrition 31:203-212. 18. Forbes, E. B., Swift, R. W., Elliott, R. F., and James, W. H. 1946.. Relation of fat to economy of food utilization. II. by the mature albino rat. J. Nutrition 31:213-227. 19. Fraps, G. S. 1913. Principles of Agricultural Chemistry. Chemical Publishing Co., Easton, Pennsylvania. 20. Fraps, G. S. 1925. Energy production coeflicients of American feeding stulfs for ruminants. Tex. Agr. Exp. Sta. Bul. 329. 21. Fraps, G. S. 1931. Digestibility by chickens of the constituents of the nitrogen-free extract of feeds. Tex. Agr. Exp. Sta. Bul. 437. 22. Fraps, G. S. 1943. Relation of the protein, fat and energy content of the ration to the composition of chickens. Poultry Sci. 22:421-424. 23. Fraps, G. S. 1943. Productive energy of certain feeds as measured by production of fat and flesh by growing rats. Texas Agr. Exp. Sta. Bul. 632. 24. Fraps, G. S. 1944. Digestibility of feeds and human foods by chickens. Tex. Agr. Exp. Sta. Bul. 663. 25. Fraps, G. S. 1944. Maintenance requirements of chickens and production energy of feeds as related to age. Texas Agr. Exp. Sta. Bul. 665. 26. Fraps, G. S. 1945. Utilization of metabolizable energy by growing chickens. Arch. Biochem. 8:21-27. " uh a <1 GL1 4 o a <5 I ~ a COMPOSITION, DIGESTIBILITY AND ENERGY OF SOME HUMAN FOODS 41 27. Fraps, G. S. 1945. Digestibility of human foods and animal feeds as measured by digestion experiments with rats. Tex. Agr. Exp. Sta. Bul. 675. 28. Fraps, G. S. 1946. Composition and productive energy of poultry feeds and rations. Tex. Exp. Sta. Bul. 678. 29. Fraps, G. S. and Carlyle, E. C. 1939. Utilization of energy of wheat products by chickens. J. Nutrition 18:385-398. 30. Fraps, G. S. and Carlyle, E. C. 1939. Energy values of corn bran, rice polish, rice bran and rye flour as measured by experiments on baby chicks. Proc. Amer. Soc. Ani. Nutr. 1939. 31. Fraps, G. S. and Carlyle, E. C. 1939. The utilization of the energy of feed by growing chickens. Texas Agr. Exp. Sta. Bul. 571. 32. Fraps, G. S. and Carlyle, E. C. 1940. Relation of gain in weight to gain in energy content of growing chickens. Jour. Agri. Res. 59:777-781. 33. Fraps, G. S., Carlyle, E. C., and Fudge, J. F. 1940. Metabolizable energy of some chicken feeds. Tex. Agr. Exp. Sta. Bul. 589. 34. Fraps, G. S. and Carlyle, E. C. 1941. Productive energy of corn meal, alfalfa leaf meal, dried buttermilk and casein as measured by production of fat and flesh 1n grow- ing chickens. Texas Agr. Exp. Sta. Bul. 600. 35. Fraps, G. S. and Carlyle, E. C. 1942. Productive energy of some feeds and foods as measured by gains of energy of growing chickens. Texas Agr. Exp. Sta. Bul. 625. 36. Frazer, A. C. 1938. Fat absorption and metabolism. Analyst 63:308. 37. Grindley, H. S., Mojonnier, T., and Porter, H. C. 1907. Studies of the elfect of dif- ferent methods of cooking upon the thoroughness and ease of digestion of meat. U. S. Department Agriculture Oflice Exp. Sta. Bul. 193. 38. Hutchinson, R. and Mottram, V. H. 1933. Food and the principles of dietetics, seventh edition. 39. Jalfa, M. E. 1903. Further investigations among fruitarians. U. S. Department Agri- culture Oflice Exp. Sta. Bul. 132. 40. Jones, J. D., Munsey, V. E. and Walker, L. E. 1942. Report of committee on protein factor. Jour. Assoc. Agr. Chem. 25:118-120. 41. Kellner, O. 1905. Die Ernahrung des landwirthschaftlicher nutztiere. 42. Kertesz, Z. I. 1940. Pectic enzymes. V. The fate of pectins in the animal body. J. Nu- trition 20:289-296. 43. Keys, Ancel. 1945. Refinement of metabolizable calculations for nutritional purposes. J. Nutrition. 29:81-84. 44. Lusk, G. 1928. The Science of Nutrition. Philadelphia. 45. Lusk, G. 1931. The specific dynamic action. J. Nutrition 23:519-529. 46. Maynard, L. A. 1944. The Atwater system of calculating the caloric value of diets. J. Nutrition 28:443-452. 46a. McCance, R. A. and Windowsen, E. M. 1940. Chemical composition of Foods (British). Chemical Publishing Co. 47. Mitchell, H. H. and Hamilton, T. S. 1929. The Biochemistry of the Amino Acids. The Chemical Catalog Company, New York. 48. Morey, N. B. 1936. Analysis and comparison of different methods of calculating the energy values of diets. Nutrition Abstracts and Reviews 6:1-12. 49. Morrison, F. B. 1936. Feeds and Feeding. The Morrison Publishing Co., Ithaca, N. Y. 50. Oshima, K. 1905. Digest of Japanese investigations on the nutrition of man. U. S. De- partment Agriculture Office Exp. Sta. Bul. 159. K 51. Phillips, M., Gross, M. J., and Browne, C. A. 1933. Determination of uronic acids and methoxyl in certain plants and plant materials. Jour. A.O.A.C. 16:289-292. 52. Schoenheimer, R. and Rittenberg, D. 1940. The study of the intermediary metabolism of animals with the aid of isotopes. Physiol. Rev. 20:218-249. 53.‘ Sherman, H. C. 1911. Chemistry of Food and Nutrition. The Macmillan Company, New York. 54. Sherman, H. C. 1941. Chemistry of Food and Nutrition, Sixth Edition. The Macmillan Company. 54a. Sheets, 0. A., McWhirter, L., Anderson, W. S., Geiger, M., Aschan, L., Cochran, H. L., Speirs, M., Reder, R., Edmond, J. B. Lease, E. J., Mitchell, J. H., Fraps, G. S., Whitacre, J., Yarnell, S. H., Ellett, W. B., Moore, R. C., and Zimmerly, H. H. 1944. The_efiect of fertilizer, soil composition and certain climatological conditions on the calcium and phosphorus content of turnip greens. Jour. Agr. Res. 68:145-189. 55. Snyder, H. 1923. The nomenclature of wheat flour. Millers National Federation, Chicago, Illinois. 56. Van Slyke, D. D. 1942. Physiology of the amino acids. Science 95:259-263. 57. Wilder, R. M. 1945. Misinterpretation and misuse of recommended dietary allowances. Science 101:285-288. 58. Wilhelmy, C. M. 1935. The specific dynamic action of food. Physiol. Rev. 15:202-220. 59. Wald, G. and Jackson, R. 1945. Emigration and food. Science News Letter for Feb- ruary 17, 1945. Nutritions Reviews February 1945.