Human Foods and Their Nutritive Value
by Harry Snyder
Previous Part     1  2  3  4  5  6     Next Part
Home - Random Browse

Some of the flavoring materials have characteristic medicinal properties, as the flavor of bitter almond, which contains hydrocyanic acid, a poisonous substance. Flavors and extracts should not be indiscriminately used. In small amounts they often exert a favorable influence upon the digestion of foods, and the value of some fruits is in a large measure due to the special flavors they contain. A study of the separate compounds which impart flavor to fruits, as the various aldehydes, ethers, and organic salts, belongs to organic chemistry rather than to foods. Some of the simpler compounds of which flavors are composed may exist in entirely different form or combination in food products; as for example, pineapple flavoring is ethyl butrate. This can be prepared by combination of butyric acid from stale butter with alcohol which supplies the ethyl radical. The chemical union of the two produces the new compound, ethyl butrate, the distinctive flavoring substance of the pineapple. Banana flavor can be made from stale butter, caustic soda, and chloroform. None of these materials, as such, go into the flavor, but an essential radical is taken from each. These manufactured products, when properly made, are in every essential similar to the flavor made by the plant and stored up in the fruit. The plant combines the material in the laboratory of the plant cell, and the manufacturer of essences puts together these same constituents in a chemical laboratory. In the fruit, however, the essential oil is associated with a number of other compounds.



73. Composition of Sugars.—The term "sugar" is applied to a large class of compounds composed of the elements carbon, hydrogen, and oxygen. Sugars used for household purposes are derived mainly from the sugar cane and the sugar beet.[25] At the present time about two fifths are obtained from the cane and about three fifths from the beet. When subjected to the same degree of refining, there is no difference in the chemical composition of the sugars from the two sources; they are alike in every respect and the chemist is unable to determine their origin. The production of sugar is an agricultural industry; the methods of manufacture pertain more to industrial chemistry than to the chemistry of foods, and therefore a discussion of them is omitted in this work.[26]

74. Commercial Grades of Sugar.—Sugars are graded according to the size of the granule, the color and general appearance of the crystals, and the per cent of sucrose or pure sugar. Common granulated sugar is from 98.5 to 99.7 per cent pure sucrose. The impurities consist mainly of moisture and mineral matter. In the process of refining, sulphur fumes are frequently used for bleaching and clarifying the solution.[26] The sulphurous acid formed is neutralized with lime, which is rendered insoluble and practically all removed in subsequent filtrations. There are, however, traces of sulphates and sulphites in ordinary sugar, but these are in such small amounts as not to be injurious to health. When sugar is burned, as in the bomb calorimeter, so as to permit collection of all of the products of combustion, granulated sugar yields about 0.01 of a per cent of sulphur dioxid.[13] Occasionally coloring substances, as a small amount of indigo, are added to yellow tinged sugars to impart a white color, much on the same principle as the bluing of clothes. The amount used is usually extremely small, and the effect on health has never been determined. Occasionally, however, bluing is used to such an extent that a blue scum appears when the sugar is boiled with water. Sugar has high value for the production of heat and energy. Digestion experiments show that when it is used in the dietary in not excessive amounts, it is directly absorbed by the body and practically all available. It can advantageously be combined with other foods to form a part of the ration.[27] When a ration contains the requisite amount of protein, sugar is used to the best advantage. Alone it is incapable of sustaining life, because it does not contain any nitrogen. When sugar was substituted for an excess of protein in a ration, it was found to produce heat and energy at much less expense. Many foods, as apples, grapes, and small fruits, contain appreciable amounts of sugar and owe their food value almost entirely to their sugar content. In the dietary, sugar is too frequently regarded as a condiment instead of a nutrient, to be used for imparting palatability rather than for purposes of nutrition. While valuable for improving the taste of foods, the main worth of sugar is as a nutritive substance; used in the preparation of foods it adds to the total heat and energy of the ration. Sugar is sometimes used in excessive amounts and, as is the case with any food or nutrient, when that occurs, nutrition disturbances result, due to misuse of the food. Statistics show that the average consumption of sugar in the United States is nearly 70 pounds a year per capita. In the dietary of the adult, sugar to the extent of four ounces per day can be consumed advantageously. The exclusion of sugar from the diet of children is a great mistake, as they need it for heat and energy and to conserve the protein for growth.

"Sugar is one of the most important forms in which carbohydrates can be added to the diet of children. The great reduction in the price of sugar which has taken place in recent years is probably one of the causes of the improved physique of the rising generation. The fear that sugar may injure children's teeth is, largely illusory. The negroes who live largely on sugar cane have the finest teeth the world can show. If injudiciously taken, sugar may, however, injure the child's appetite and digestion. The craving for sweets which children show is no doubt the natural expression of a physiological need, but they should be taken with, and not between, meals."[28]

75. Sugar in the Dietary.—Sugar has an important place in the dietary. It not only serves for the production of heat and energy in the body, but is also valuable in enabling the proteids to be used more economically. In reasonable amounts, it is particularly valuable in the dietary of growing children, as the proteids of the food are then utilized to better advantage for growth. The unique value of sugar depends upon its intelligent use and its proper combination with other foods, particularly with those rich in the nitrogenous compounds or proteids. Sugar alone is incapable of sustaining life, but combined with other foods is a valuable nutrient. The amount which can be advantageously used depends largely upon the individual. Ordinarily three to five ounces per day is sufficient, although some persons cannot safely consume as much as this. In the case of diabetes mellitus, the amount of sugar in the ration must be materially reduced. Persons in normal health and engaged in outdoor work can use sugar to advantage.[29] Many of the "harvest drinks," made largely from molasses with a little ginger, and used extensively in some localities, are not without merit, as they contain an appreciable amount of nutrients. Milk contains more sugar as lactose or milk sugar than any other nutrient.

The craving for sugar by growing children and athletes is natural. Sugar, however, is often injudiciously used, and a perverted taste may be established which can be satisfied only by excessive amounts. This results in impaired digestion and malnutrition.

76. Maple Sugar.—Sugar obtained by evaporation from the sap of the maple tree (Acer saccharinum) is identical, except for the foreign substances which it contains, with that from the beet and sugar cane. The mottled appearance and characteristic color and taste of maple sugar are due to the various organic acids and other compounds present in the maple sap and recovered in the sugar. Maple sugar, as ordinarily prepared, has 0.4 of a per cent or more of ash or mineral matter, while refined cane sugar contains less than one tenth as much.[30] Hence, when maple sugar is adulterated with cane and beet sugars, the ash content is noticeably lowered, as is also the content of organic acids. It is difficult, however, to determine with absolute certainty pure high grade maple sugar from the impure low grade to which a small amount of granulated sugar has been added.

77. Adulteration of Sugar.—Sugar at the present time is not materially adulterated. Other than the substances mentioned which are used for clarification and color, none are added during refining which remain in the sugar in appreciable amounts. Sugar does not readily lend itself to adulteration, as it has a definite crystalline structure, and materials that would be suitable for its adulteration are of entirely different physical character.[31] Cane sugar is not easily blended with glucose, or starch sugar, because of the physical differences between the two. The question of the kind of sugar to use in the household, as granulated, loaf, or pulverized, is largely one of personal choice, as there is no appreciable difference in the nutritive value or purity of the different kinds.

78. Dextrose Sugars.—Products known as glucose and dextrose sugars are made from corn and other starches; they can also be prepared from cane sugar by the use of heat, chemicals, or ferments for carrying on the process known as inversion. The dextrose sugars differ from cane sugar in containing a dissimilar number of carbon, hydrogen, and oxygen atoms in the molecule. The formula of the dextrose sugars is C_{6}H_{12}_O{6}, while that of cane sugar is C_{12}H_{22}O_{11}. By the addition of one molecule of water, H_{2}O, to a molecule of sucrose, two molecules of invert sugar (dextrose and glucose) are produced:[1] C_{12}H_{22}O_{11} + H_{2} = C_{6}H_{12}O_{6} + C_{6}H_{12}O_{6}. In bringing about this change, acids are employed, but the acid in no way enters into the chemical composition of the final product; it is removed as described during the process of sugar manufacture. The action of the acid brings about a catalytic change, the acid being necessary only as a presence reagent to start the chemical reaction. When properly prepared and the acid product thoroughly removed, dextrose and glucose have practically the same food value as sugar. When they are digested, heat and energy are produced, and a given weight has about the same fuel value as an equal weight of sugar. Some of the glucose-yielding products can be made at less expense than sugar, and when they are sold under their right names there is no reason why they should not be used in the dietary, as they serve the same nutritive purpose.

79. Molasses is a by-product obtained in the refining of sugar. It is a mixture of cane sugar and invert sugars, as levulose and dextrose. When in sugar making the sucrose is removed by crystallization, a point is finally reached where the solution, or mother liquid, as it is called, refuses to give up any further crystals;[31] then this product, consisting of various sugars and small amounts of organic acids and ash, is partially refined and clarified to form molasses. The term "New Orleans" molasses was formerly applied to the product obtained by the use of open kettles for the manufacture of sugar, but during recent years the vacuum pan process has been introduced, and "New Orleans" molasses is now an entirely different article. The terms first, second, and third molasses are applied to the liquids obtained after the removal of the first, second, and third crops of sugar crystals; first molasses being richer in sucrose, while third molasses is richer in dextrose and invert sugars. The ash in molasses ranges from 4 to 6.5 per cent. Some of the low grades of molasses are used in the preparation of animal foods.

The taste and physical characteristics of molasses are due largely to the organic acids and impurities that are present, as well as to the proportion in which the various sugars occur. When used with soda in cooking and baking operations, the organic acid of the molasses liberates carbon dioxide gas, which acts as a leavening agent. Because of the organic acids, molasses should not be stored in tin or metalware dishes, as the solvent action results in producing poisonous tin and other metallic salts.

The food value of molasses is dependent entirely upon the amount of dry matter and the per cent of sugar. A large amount of water is considered an adulterant; ordinarily molasses contains from 20 to 33 per cent. If a sample of molasses contains 75 per cent of dry matter, it has slightly less than three fourths of the nutritive value of the same weight of sugar.

80. Syrups.—The term "syrup" is applied to natural products obtained by evaporation and purification of the saccharine juices of plants. Sorghum syrup is from the sorghum plant, which is pressed by machinery and the juice clarified and evaporated so as to contain about 25 per cent of water. In sorghum syrups there are from 30 to 45 per cent of cane sugar, and from 12 to 20 per cent of glucose and invert sugars. Cane syrup is made from the clarified juice of the sugar cane, and has about the same general composition as sorghum syrup. Maple syrup, prepared from the juice of the sugar maple, is characteristically rich in sucrose and contains but little glucose or reducing sugars. The flavor of all the syrups is due mainly to organic acids, ethereal products, and impurities. In some instances the essential flavor can be produced synthetically, or derived from other and cheaper materials; and by the use of these flavors, mixed syrups can be prepared closely resembling many of the natural products. When properly made, they are equal in nutritive value to natural syrups. When sold under assumed names, they are to be considered and classified as adulterated, and not as syrups from definite and specific products. Low-grade syrups and molasses are often used for making fuel alcohol. They readily undergo alcoholic fermentation and are valuable for this purpose, rendering it possible for a good grade of fuel alcohol to be produced at low cost. The manufacture of sugar, syrups, and molasses has been brought to a high degree of perfection through the assistance rendered by industrial chemistry. Losses in the process are reduced to a minimum, and the various steps are all controlled by chemical analysis. Sugar has the physical property of deflecting a ray of polarized light, the amount of deflection depending upon the quantity of sugar in solution. This is measured by the polariscope, an instrument by means of which the sugar content of sugar plants is rapidly determined.

81. Honey is composed largely of invert sugars gathered by the honeybee from the nectar of flowers. It varies in composition and flavor according to its source. The color depends upon the flower from which it came, white clover giving a light-colored, pleasant-flavored honey, while that from buckwheat and goldenrod is dark and has a slightly rank taste. The comb is composed largely of wax, which has somewhat the same general composition as fat, but contains ethereal instead of glycerol bodies. On account of the predominance of invert sugars, pure honey has a levulo or left-handed rotation when examined by the polariscope. Honey contains from 60 to 75 per cent of invert sugars, and from 12 to 20 per cent of water, while the ash content is small, less than one tenth of one per cent. Strained honey is easily adulterated with glucose products. Adulteration with cane sugar is readily detected, as pure honey contains only a very small amount of sucrose. Honey can be made by feeding bees on sugar; the sugar undergoes inversion, with the production of dextrose. Such honey, although not adulterated, is inferior in quality and lacking in natural flavor.[18]

82. Confections.—By blending various saccharine products, confections are made. Usually sucrose (cane and beet sugar) is used as the basis for their preparation. Sucrose has definite physical properties, as crystalline structure, and forms chemical and mechanical combinations with acid, alkaline, and other substances; it also unites with water, and when heated undergoes changes in structural composition. The presence of small amounts of acid substances, or variations in the concentration of the sugar solution, materially affect the mechanical relation of the sugar particles to each other, and their crystallization. Usually crystallization takes place when there is less than 25 per cent of water present. The form, size, and arrangement of the crystals are influenced by agitation during cooling. To secure desired results, often small quantities of various other substances are employed for their mechanical action. Glucose is frequently used, and is said to be necessary for the production of some kinds of candy.

Candies are colored with various dyes and pigments, many of which are harmless, although some are injurious. Coal tar dyes are frequently employed for this purpose. Objection has generally been urged against their use, as it is believed many of them are injurious to health. It cannot be said, however, that all are poisonous, as some are known to be harmless. The use of a few coal tar dyes is allowed by the United States government. Mineral colors are now rarely, if ever, used.

Impure candies result from objectionable ingredients, as starch, paraffin, and large amounts of injurious coloring substances. Coal tar coloring materials are identified in the way described in Experiment No. 13. Confectionery, when properly prepared and unadulterated, has the same nutritive value as sugar and the other ingredients, and is entitled to a place in the dietary for the production of heat and energy. Much larger amounts of candies are sold and consumed during the winter than the summer months, suggesting that in cold weather candy is most needed in the dietary.

83. Saccharine is an artificial sweetening, five hundred times sweeter than cane sugar. It contains in its molecule, chemically united, benzine, sulphuric acid, and ammonia radicals. It is employed for sweetening purposes in cases of diabetes mellitus, where physicians advise against the use of sugar. It has no food value. A small amount is sometimes added to canned corn and tomatoes to impart a sweet taste. The physiological properties of saccharine have not been extensively investigated.



84. General Composition of Legumes.—Peas, beans, lentils, and peanuts are the legumes most generally used for human food. As a class, they are characterized by high protein content and a comparatively low per cent of starch and carbohydrates. They contain the largest amount of nitrogenous compounds of any of the vegetable foods, and hence are particularly valuable in the human ration as a substitute for meats.[32] For feeding animals the legumes are highly prized, particularly the forage crops, clover and alfalfa. These secure their nitrogen, which is the characteristic element of protein, from the free nitrogen of the air, through the workings of bacterial organisms found in the nodules on the roots of the plants. The legumes appear to be the only plants capable of making use of the nitrogen of the air for food purposes.

85. Beans contain about 24 per cent of protein and but little fat, less than is found in any of the grain or cereal products. The protein of the bean differs from that of cereals in its general and structural composition. It is a globulin known as legumin, and is acted upon mainly by ferments working in alkaline solutions, as in the lower part of the digestive tract. Beans have about the same amount of ash as the cereals, but the ash is richer in potash and lime.

86. Digestibility of Beans.—Beans are usually considered indigestible, but experiments show they are quite completely digested, although they require more work on the part of the digestive tract than many other foods. The digestibility was found to vary with individuals, 86 per cent of the protein being digested in one case, and only 72 per cent in another. The protein of beans is not as completely digested as that of meats. When beans were combined with other foods, forming a part of a ration, they were more completely digested than when used in large amounts and with only a few other foods. The presence of the skin is in part responsible for low digestibility. When in the preparation of beans the skins, which contain a large amount of cellulose, are removed, the beans are more completely digested. By cooking from twenty minutes to half an hour in rapidly boiling water containing a small amount of soda, the skins are softened and loosened and are then easily removed by rubbing in cold water. Some of the soda enters into combination with the legumin. Along with the skins a portion of the germ is lost. The germ readily ferments, which is probably the cause of beans producing flatulence with some individuals during digestion. After the skins are removed the nutrients are more susceptible to the action of the digestive fluids. Experiments show that 42 per cent of the protein of baked skinned beans is soluble in pepsin and pancreatin solutions, while under similar conditions there is only 3.85 per cent of the protein soluble from beans baked without removal of the skins.

87. Use of Beans in the Dietary.—There is no vegetable food capable of furnishing so much protein at such low cost as beans; from a pound costing five cents about one fifth of a pound of protein and three fifths of a pound of carbohydrates are obtained. Beans can, to a great extent, take the place of meats in the dietary. There is more protein in beans than in beef. Four ounces of uncooked beans or six ounces of baked beans are as much as can conveniently be combined in the dietary, and these will furnish a quarter of the protein of the ration. In the case of active out-of-door laborers over a pound of baked beans per day is often consumed with impunity.

88. String Beans.—String beans—green beans with pod—contain a large amount of water, 85 to 88 per cent. The dry matter is rich in protein, nearly 20 per cent, although in the green beans as eaten, containing 85 per cent water, there is less than 2-1/2 per cent. Lima beans are richer in protein than string beans, as the green pod is not included. String beans are valuable both for the nutrients they contain and for the favorable influence they exert upon the digestibility of other foods.

89. Peas.—In general composition and digestibility, peas are quite similar to beans. They belong to the same family, Leguminosae, and the protein of each is similar in quantity and general properties. The statements made in regard to the composition, digestibility, and use of beans in the dietary apply with minor modifications to peas. When used in the preparation of soups, they add appreciable amounts of nutrients.

90. Canned Peas.—In order to impart a rich green color, copper sulphate has been used in the canning of peas. Physiologists differ as to its effect upon health. While a little may not be particularly injurious, much interferes with normal digestion of the food and forms insoluble copper proteids. In some countries a small amount of copper sulphate is tolerated, while in others it is prohibited.

91. Peanuts.—Peanuts differ from peas and beans in containing more fat. They should be considered a food, for at ordinary prices they furnish a large amount of protein and fat. Like the other members of the legume family, the peanut is rather slow of digestion and requires considerable intestinal work for completion of the process.


92. General Composition.—Nuts should be regarded as food, for they contribute to a ration appreciable amounts of nutrients. The edible portion of nearly all is rich in fat; pecans, for example, contain as high as 70 per cent. In protein content nuts range from 3 per cent in cocoanuts to 30 per cent in peanuts. The carbohydrate content is usually comparatively low, less than 5 per cent in hickory nuts, although there is nearly 40 per cent in chestnuts. On account of high fat content, nuts supply a large amount of heat and energy.[33]

93. Chestnuts are characterized by containing less fat and protein and much more carbohydrate material, especially starch, than is found in other nuts. In southern Europe chestnuts are widely used as food; the skins are removed, and the nuts are steamed, boiled, or roasted, and sometimes they are dried and ground into flour. Chestnuts are less concentrated in protein and fat, and form a better balanced food used alone than do other nuts.

94. The Hickory Nut, which is a characteristically American nut, contains in the edible portion about 15 per cent protein, 65 per cent fat, and 12 per cent carbohydrates.

95. The Almonds used in the United States come chiefly from southern Europe, although they are successfully raised in California. They contain about 55 per cent fat and 22 per cent protein. The flavor of almonds is due to a small amount of hydrocyanic acid.

96. Pistachio.—Some nuts are used for imparting color and flavor to food products, as the pistachio nut, the kernel of which is greenish in color and imparts a flavor suggestive of almonds. The pistachio has high food value, as it is rich in both fat and protein. It is employed in the manufacture of confectionery and in ice cream for imparting flavor and color.

97. Cocoanuts grow luxuriantly in many tropical countries, and have a high food value. They are characteristically rich in fat, one half of the edible portion being composed of this nutrient. For tropical countries they supply the fat of a ration at less expense than any other food. When used in large amounts they should be supplemented with foods rich in carbohydrates, as rice, and in proteids, as beans. Cocoanut milk is proportionally richer in carbohydrates and poorer in fat and protein than the meat of the cocoanut. In discussing the cocoanut, Woods states:[34]

"The small, green, and immature nuts are grated fine for medicinal use, and when mixed with the oil of the ripe nut it becomes a healing ointment. The jelly which lines the shell of the more mature nut furnishes a delicate and nutritious food. The milk in its center, when iced, is a most delicious luxury. Grated cocoanut forms a part of the world-renowned East India condiment, curry. Dried, shredded (desiccated) cocoanut is an important article of commerce. From the oil a butter is made, of a clear, whitish color, so rich in fat, that of water and foreign substances combined there are but O.0068. It is better adapted for cooking than for table use. At present it is chiefly used in hospitals, but it is rapidly finding its way to the tables of the poor, particularly as a substitute for oleomargarine."

98. Use of Nuts in the Dietary.—When nuts can be secured at a low price per pound, ten cents or less, they compare favorably in nutritive value with other staple foods. Digestion experiments with rations composed largely of nuts show that they are quite thoroughly digested. Professor Jaffa of the California Experiment Station, in discussing the nutritive value of nuts and fruits, says:[35]

"It is certainly an error to consider nuts merely as an accessory to an already heavy meal, and to regard fruit merely as something of value for its pleasant flavor, or for its hygienic or medicinal virtues. The agreement of one food or another with any person is more or less a personal idiosyncrasy, but it seems fair to say that those with whom nuts and fruits agree, can, if they desire, readily secure a considerable part of their nutritive material from such sources."


(From Fifteenth Annual Report, Maine Agricultural Experiment Station.)

=========================================================================== REFUSE EDIBLE EDIBLE PORTION VALUE[A] PORTION Water Prot. Fat Carb. Ash PER LB. - % % % % % % % Calories Almonds 64.8 35.2 1.7 7.3 19.3 6.2 0.7 1065 Almonds, kernels 100.0 4.8 21.0 54.9 17.3 2.0 3030 Brazil nuts 49.6 50.4 2.7 8.6 33.6 3.5 2.0 1545 Filberts 52.1 47.9 1.8 7.5 31.3 6.2 1.1 1575 Filberts, kernels 100.0 3.7 15.6 65.3 13.0 2.4 3290 Hickory nuts 62.2 37.8 1.4 5.8 25.5 4.3 0.8 1265 Pecans 49.7 50.3 1.4 5.2 35.6 7.2 0.8 1733 Pecans, kernels 100.0 2.9 10.3 70.8 14.3 1.7 3445 Walnuts 58.0 42.0 1.2 7.0 27.0 6.1 0.7 1385 Walnuts, kernels 100.0 2.8 16.7 64.4 14.8 1.3 3305 Chestnuts 16.1 83.9 31.0 5.7 6.7 39.0 1.5 1115 Acorns 35.6 64.4 2.6 5.2 24.1 30.9 1.6 1690 Beechnuts 40.8 59.2 2.3 13.0 34.0 7.8 2.1 1820 Butternuts 86.4 13.6 0.6 3.8 8.3 0.5 0.4 430 Litchi nuts 41.6 58.4 10.5 1.7 0.1 45.2 0.9 875 Pinon, P. edulis 40.6 59.4 2.0 8.7 36.8 10.2 1.7 1905 Pinon, P. monophylla 41.7 58.3 2.2 3.8 35.4 15.3 1.6 1850 Pinon, P. sabiniana 77.0 23.0 1.2 6.5 12.3 1.9 1.1 675 Pistachio, kernels 100.0 4.2 22.6 54.5 15.6 3.1 3010 Peanuts, raw 26.4 73.6 6.9 20.6 30.7 13.8 1.6 1935 Peanuts, kernels 100.0 9.3 27.9 42.0 18.7 2.1 2640 Roasted peanuts 32.6 67.4 1.1 20.6 33.1 10.9 1.7 1985 Shelled peanuts 100.0 1.6 30.5 49.2 16.2 2.5 2955 Peanut butter 2.0 29.3 46.6 17.1 [B]5.0 2830 Cocoanuts 48.8 51.2 7.2 2.9 25.9 14.3 0.9 1415 Cocoanuts, shredded 3.5 6.3 57.3 31.6 1.3 3125 Cocoanut milk 92.7 0.4 1.5 4.6 0.8 97 =========================================================================

[Footnote A: Calculated from analyses.]

[Footnote B: Including salt, 4.1.]



99. Importance in the Dietary.—There is no article of food which enters so extensively into the dietary as milk, and it is one of the few foods which supply all the nutrients,—fats, carbohydrates, and proteids.[36] Milk alone is capable of sustaining life for comparatively long periods, and it is the chief article of food during many diseases. An exclusive milk diet for a healthy adult, however, would be unsatisfactory; in the case of young children, milk is essential, because the digestive tract has not become functionally developed for the digestion of other foods.

It is necessary to consider not only the composition and nutritive value of milk, but also its purity or sanitary condition.

100. General Composition.—Average milk contains about 87 per cent water and 13 per cent dry matter. The dry matter is composed approximately of:

======================= Per Cent Fat 3.5 Casein 3.25 Albumin 0.50 Milk sugar 5.00 Ash 0.75 =======================

Fat is the most variable constituent of milk. Occasionally it is found as low as 2 per cent and as high as 6 per cent or more. The poorest and richest milks differ mainly in fat content, as the sugar, ash, casein, and albumin, or "solids of the milk serum," are fairly constant in amount and composition. Variations in the content of fat are due to differences in feed and in the breed and individuality of the animal.

101. Digestibility.—Milk is one of the most completely digested of foods, about 95 per cent of the protein and fat and 97 per cent of the carbohydrates being absorbed and utilized by the body.

In a mixed ration, the nutrients of milk are practically all absorbed. Milk also exerts a favorable influence upon the digestibility of other foods with which it is combined. This is doubtless due to the digestive action of the special ferments or enzymes which milk contains. In milk there is a soluble ferment material or enzyme which has the power of peptonizing proteids. It is this ferment which carries on the ripening process when cheese is cured in cold storage, and it is believed to be this body which promotes digestion of other foods with which milk is combined.[27]

Milk is not easily digested by some persons. The tendency to costiveness caused by a milk diet can be largely overcome by the use of salt with the milk, or of some solid food, as toast or crackers, to prevent coagulation and the formation of masses resistant to the digestive fluids. Barley water and lime water in small amounts are also useful for assisting mechanically in the digestion of milk. Milk at ordinary prices is one of the cheapest foods that can be used.

102. Sanitary Condition of Milk.—Equally as important as composition is the sanitary condition or wholesomeness of milk. Milk is a food material which readily undergoes fermentation and is a medium for the distribution of germ diseases. The conditions under which it is produced and the way in which it is handled determine largely its sanitary value, and are of so much importance in relation to public health that during recent years city and state boards of health have introduced sanitary inspection and examination of milk along with the chemical tests for detecting its adulteration. Some of the more frequent causes of contaminated and unsound milk are: unhealthy animals, poor food and water, unsanitary surroundings of the animals, and lack of cleanliness and care in the handling and transporting of the milk. Outbreaks of typhoid and scarlet fevers and other germ diseases have frequently been traced to a contaminated milk supply.[37]

103. Certified Milk.—When milk is produced under the most sanitary conditions, the number of bacterial bodies per cubic centimeter is materially reduced. In order to supply high grade milk containing but few bacteria, special precautions are taken in the care of the animals, and in the feeding and milking, and all sources of contamination of the milk are eliminated as far as possible. Such milk, when sold in sterilized bottles, is commonly called "certified milk," indicating that its purity is guaranteed by the producer and that the number of bacteria per unit does not exceed a certain standard, as 8000 per cubic centimeter. Ordinary market milk contains upwards of 50,000.

104. Pasteurized Milk.—In order to destroy the activity of the bacterial organisms, milk is subjected to a temperature of 157 deg. F. for ten minutes or longer, which process is known as pasteurization. When milk is heated to a temperature above 180 deg., it is sterilized. Below 157 deg., the albumin is not coagulated. By pasteurizing, milk is much improved from a sanitary point of view, and whenever the milk supply is of unknown purity, it should be pasteurized.[38] After the milk has been thus treated, the same care should be exercised in keeping it protected to prevent fresh inoculation or contamination, as though it were unpasteurized milk. For family use milk can be pasteurized in small amounts in the following way: Before receiving the milk, the receptacle should be thoroughly cleaned and sterilized with boiling water or dry heat, as in an oven. The milk is loosely covered and placed in a pan of water, a false bottom being in the pan so as to prevent unequal heating. The water surrounding the milk is gradually heated until a temperature of 159 deg. F. is registered, and the milk is kept at this temperature for about ten minutes. It is then cooled and placed in the refrigerator.

105. Tyrotoxicon.—Tyrotoxicon is a chemical compound produced by a ferment body which finds its way into milk when kept in unsanitary surroundings. It induces digestion disorders similar to cholera, and when present in large amounts, may prove fatal. It sometimes develops in cream, ice cream, or cheese, but only when they have been kept in unclean places or produced from infected milk.

601. Color of Milk is often taken as a guide to its purity and richness in fat. While a yellow tinge is usually characteristic of milks rich in fat, it is not a hard and fast rule, for frequently light-colored milks are richer in fat than yellow-tinged ones. The coloring material is independent of the percentage of fat, and it is not always safe to judge the richness of milk on the basis of color.

107. Souring of Milk.—Souring of milk is due to the action of the lactic acid organism, which finds its way into the milk through particles of dust carried in the air or from unclean receptacles which contain the spores of the organism.[39] When milk sours, a small amount of sugar is changed to lactic acid which reacts upon the casein, converting it from a soluble to an insoluble condition. When milk is exposed to the air at a temperature of from 70 deg. to 90 deg. F., lactic acid fermentation readily takes place. At a low temperature the process is checked, and at a high temperature the organisms and spores are destroyed. In addition to lactic acid ferments, there are large numbers of others which develop in milk, changing the different compounds of which milk is composed. In the processes of butter and cheese making, these fermentation changes are controlled so as to develop the flavor and secure the best grades of butter and cheese.

108. Use of Preservatives in Milk.—In order to check fermentation, boric acid, formalin, and other preservatives have been proposed. Physiologists object to their use because the quantity required to prevent fermentation is often sufficient to have a medicinal effect. The tendency is to use excessive amounts, which may interfere with normal digestion of the food. Milk that is cared for under the most sanitary conditions has a higher dietetic value and is much to be preferred to that which has been kept sweet by the use of preservatives.

109. Condensed Milk is prepared by evaporating milk in vacuum pans until it is reduced about one fourth in bulk, when it is sealed in cans, and it will then keep sweet for a long time. Occasionally some cane sugar is added to the evaporated product. When diluted, evaporated milk has much the same composition as whole milk. When a can of condensed milk has been opened, the same care should be exercised to prevent fermentation as if it were fresh milk.

110. Skim Milk differs in composition from whole milk in fat content. When the fat is removed by the separator, there is often left less than one tenth of a per cent. Skim milk has a much higher nutritive value than is generally conceded, and wherever it can be procured at a reasonable price it should be used in the dietary as a source of protein.

111. Cream ranges in fat content from 15 to 35 per cent. It is generally preferred to whole milk, although it is not as well balanced a food, because it is deficient in protein. Cream should contain at least 25 per cent of fat.

112. Buttermilk is the product left after removal of the fat from cream by churning. It has about the same amount of nutrients as skim milk. The casein is in a slightly modified form due to the development of lactic acid during the ripening of the cream, and on this account buttermilk is more easily digested and assimilated by many individuals than milk in other forms. The development of the acid generally reduces the number of species of other than the lactic organisms, and these are increased.

113. Goat's Milk is somewhat richer in solids than cow's milk, containing about one per cent more proteids, a little more fat, and less sugar. When used as a substitute for human or cow's milk, it generally needs to be slightly diluted, depending, however, upon the composition of the individual sample.

114. Koumiss is a fermented beverage made from milk by the use of yeast to secure alcoholic fermentation. Koumiss contains about one per cent each of lactic acid and alcohol, and the casein and other nutrients are somewhat modified by the fermentation changes. Koumiss is generally considered a non-alcoholic beverage possessing both food and dietetic value.

115. Prepared Milks.—Various preparations are made to resemble milk in general composition. These are mechanical mixtures of sugar, fats, and proteids. Milk sugar, casein, or malted proteids are generally the materials employed in their preparation. Often the dried and pulverized solids of skim milk are used. Many of the prepared milks are deficient in fat. While they are not equal to cow's milk, their use is often made necessary from force of circumstances.

116. Human Milk is not as rich in solid matter as cow's milk. It contains about the same amount of fat, one per cent more sugar, and one per cent less proteids. In human milk nearly one half of the protein is in the form of albumins, while in cow's milk there is about one fifth in this form. The fat globules are much smaller than those of cow's milk. In infant feeding it is often necessary to modify cow's milk by the addition of water, cream, and milk sugar, so as to make it more nearly resemble in composition human milk.

117. Adulteration of Milk.—Milk is not as extensively adulterated as it was before the passage and enforcement of the numerous state and municipal laws regulating its inspection and sale. The most frequent forms of adulteration are addition of water and removal of cream. These are readily detected from the specific gravity and fat content of the milk. The specific gravity of milk is determined by means of the lactometer, an instrument which sinks to a definite point in pure milk. In watered milk it sinks to greater depth, depending upon the amount of water added. The fat content of milk is readily and accurately determined by the Babcock test, in which the fat is separated by centrifugal action. For the detection of adulterated milk the student is referred to Chapter VI, "Chemistry of Dairying," by Snyder.


118. Composition.—Butter is made by the churning or agitation of cream and is composed mainly of milk fats and water, together with smaller amounts of ash, salt, casein, milk sugar, and lactic acid. Average butter has the following composition:

============================ Per Cent Water 10.5 Ash and salt 2.5 Casein and albumin 1.0 Fat 86.0 ============================

When butter contains an abnormal amount of water, it is considered adulterated. According to act of Congress standard butter should not contain over 16 per cent of water nor less than 82.5 per cent of fat.

119. Digestibility of Butter.—Digestion experiments show that practically all of the fat, 98 per cent, is digestible and available for use by the body. Butter is valuable only for the production of heat and energy. Alone, it is incapable of sustaining life, because it contains no proteid material. It is usually one of the more expensive items of food, but it is generally considered quite necessary in a ration.[5] It has been suggested that it takes an important part mechanically in the digestion of food.

120. Adulteration of Butter.—In addition to containing an excess of water, butter is adulterated in other ways. Old, stale butter is occasionally melted, washed, salted, and reworked. This product is known as renovated butter, and has poor keeping qualities. Frequently preservatives are added to such butter to delay fermentation changes. Oleomargarine and butterine are made by mixing vegetable and animal fats.[40] Highly colored stearin, cotton-seed oil, and lard are the usual materials from which oleomargarine is made. It has practically the same composition, digestibility, and food value as butter. When sold under its true name and not as butter, there is no objection, as it is a valuable food and supplies heat and energy at less cost than butter. The main objection to oleomargarine and butterine is that they are sold as butter.[41]

The coloring of butter is not generally looked upon as adulteration, for butter naturally has a more or less yellow tinge. According to an act of Congress, butter colors of a non-injurious character are allowed to be used.


121. General Composition.—Cheese, is made by the addition of rennet to ripened milk, resulting in coagulation of the casein, which mechanically combines with the fat. It differs from butter in composition by containing, in addition to fat, casein and appreciable amounts of mineral matter. The composition varies with the character of the milk from which the cheese was made. Average milk produces cheese containing a larger amount of fat than proteids, while cheese from skimmed or partially skimmed milk is proportionally poorer in fat. Ordinarily there is about 35 per cent of water, 33 per cent of fat, and 27 per cent of casein, and albumin or milk proteids, the remainder being ash, salt, milk sugar, and lactic acid. Cheese is characterized by its large percentage of both fat and protein, and has high food value. It contains more fat and protein than any of the meats; in fact, there are but few foods which have such liberal amounts of these nutrients as cheese.

The odor and flavor of cheese are due to workings of bacteria which result in the production of aromatic compounds. The purity and condition of the milk, as well as the method of manufacture and the kind of ferment material used, determine largely the flavor and odor. Cheese is generally allowed to undergo a ripening or curing process before it is used as food. The changes resulting consist mainly in increased solubility of the proteids, with the formation of a small amount of amid and aromatic compounds.[42]

122. Digestibility.—Cheese is popularly considered an indigestible food, but extended experiments show that it is quite completely digested, although in the case of some individuals not easily digested. In general, about 95 per cent of the fat and 92 per cent and more of the protein is digested, depending upon the general composition of the cheese and the digestive capacity of the individual. As far as total digestibility is concerned, there appears to be but little difference between green and well-cured cheese. So far as ease of digestion is concerned, it is probable that some difference exists. There is also but little difference in digestibility resulting from the way in which milk is made into cheese, the nutrients of Roquefort, Swiss, Camembert, and Cheddar being about equally digestible.[13] The differences in odor and taste are due to variations in kind and amount of bacterial action. When combined with other foods, cheese may exercise a beneficial influence upon digestion in the same way as noted from the use of several foods in a ration. No material differences were observed in digestibility when cheese was used in small amounts, as for condimental purposes, or when used in large amounts to furnish nutrients. Artificial digestion experiments show that cheese is more readily acted upon by the pancreatic than by the gastric fluids, suggesting that cheese undergoes intestinal rather than gastric digestion. It is possible this is the reason that cheese is slow of digestion in the case of some individuals.

123. Use in the Dietary.—Cheese should be used in the dietary regularly and in reasonable amounts, rather than irregularly and then in large amounts. Cheese is not a luxury, but ordinarily it is one of the cheapest and most nutritious of human foods. A pound of cheese costing 15 cents contains about a quarter of a pound of protein and a third of a pound of fat; at the same price, beef yields only about half as much fat and less protein. Cheese at 18 cents per pound furnishes more available nutrients and energy than beef at 12 cents per pound. In the dietary of European armies, cheese to a great extent takes the place of beef. See Chapter XVI.

124. Cottage Cheese is made by coagulating milk and preparing the curd by mixing with it cream or melted butter and salt or sugar as desired. When milk can be procured at little cost, cottage cheese is one of the cheapest and most valuable foods.[43]

125. Different Kinds of Cheese.—By the use of different kinds of ferments and variations in the process of manufacture different types or kinds of cheese are made, as Roquefort, Swiss, Edam, Stilton, Camembert, etc. In the manufacture of Roquefort cheese, which is made from goats' and ewes' milk, bread is added and the cheese is cured in caves, resulting in the formation of a green mold which penetrates the cheese mass, and produces characteristic odor and flavor. Stilton is an English soft, rich cheese of mild flavor, made from milk to which cream is usually added. It is allowed to undergo an extended process of ripening, often resulting in the formation of bluish green threads of fungus. Limburger owes its characteristic odor and flavor to the action of special ferment bodies which carry on the ripening process. Neufchatel is a soft cheese made from sweet milk to which the rennet is added at a high temperature. After pressing, it is kneaded and worked, and then put into packages and covered with tin foil.

126. Adulteration of Cheese.—The most common forms of adulteration are the manufacture of skim-milk cheese by the removal of the fat from the milk, and substitution of cheaper and foreign fats, making a product known as filled cheese. When not labeled whole milk cheese, or sold as such, there is no objection to skim-milk cheese. It has a high food value and is often a cheap source of protein. The manufacture of filled cheese is now regulated by the national government, and all such cheese must pay a special tax and be properly labeled. As a result, the amount of filled cheese upon the market has very greatly decreased, and cheese is now less adulterated than in former years. The national dairy law allows the use of coloring matter of a harmless nature in the manufacture of cheese.

127. Dairy Products in the Dietary.—The nutrients in milk are produced at less expense for grain and forage than the nutrients in beef, hence from a pecuniary point of view, dairy products, as milk and cheese, have the advantage. In the case of butter, however, the cost usually exceeds that of meat. In older agricultural regions, where the cost of beef production reaches the maximum, dairying is generally resorted to, as it yields larger financial returns, and as a result more cheese and less beef are used in the dietary. As the cost of meats is enhanced, dairy products, as cheese, naturally take their place.



128. General Composition.—Animal tissue is composed of the same classes of compounds as plant tissue. In each, water makes up a large portion of the weight, and the dry matter is composed of nitrogenous and non-nitrogenous compounds, and ash or mineral matter. Plants and animals differ in composition not so much as to the kinds of compounds, although there are differences, but more in the percentage amounts of these compounds. In plants, with the exception of the legumes, the protein rarely exceeds 14 per cent, and in many vegetable foods, when prepared for the table, there is less than 2 per cent. In meats the protein ranges from 15 to 20 per cent. The non-nitrogenous compounds of plants are present mainly in the form of starch, sugar, and cellulose, while in animal bodies there are only traces of carbohydrates, but large amounts of fat. Fat is the chief non-nitrogenous compound of meats; it ranges between quite wide limits, depending upon kind, age, and general condition of the animal. Meats contain the same general classes of proteins as the vegetable foods; in each the proteins are made up of albumins, glubulins, albuminates, peptone-like bodies, and insoluble proteids. The larger portion of the protein of meats and cereals is in insoluble forms. The meat juices, which contain the soluble portion of the proteins, constitute less than 5 percent of the nitrogenous compounds. Meats contain less amid substances than plants, in which the amids are produced from ammonium compounds and are supposed to be intermediate products in the formation of proteids, while in the animal body they are derived from the proteids supplied in the food and, it is generally believed, cannot form proteids. Albuminoids make up the connective tissue, hair, and skin, and are more abundant in animal than in plant tissue. One of the chief albuminoids is gelatine. Both plant and animal foods undergo bacterial changes resulting in the production of alkaloidal bodies known as ptomaines, of which there are a large number. These are poisonous and are what cause putrid and stale meat to be unwholesome. The protein in meat differs little in general composition from that of vegetable origin; differences in structure and cleavage products between the two are, however, noticeable.

While meats from different kinds of animals have somewhat the same general composition, they differ in physical properties, and also in the nature of the various nutrients. For example, pork contains less protein than beef, but the protein of pork is materially different from that of beef, as a larger portion is in the form of soluble proteids, while in beef more is present in an insoluble form. Not only are differences in the percentage of individual proteins noticeable, but there are equally as great differences in the fats. As for example: some of the meats have a larger proportion of the fat as stearin than do others. Hence meats differ in texture and taste more than in nutritive value, due to the variations in the percentage of the different proteins, fats, and extractive material, rather than to differences in the total amounts of these compounds. The taste and flavor of meat is to a large extent influenced by the amount of extractive material.

While the nutrients of meats are divided into classes, as proteins and fats, there are a large number of separate compounds which make up each of the individual classes, and there are also small amounts of compounds which are not included in these groups.

129. Beef.—About one half of the weight of beef is water; the lean meat contains a much larger amount than the fat. As a rule, the parts of the animal that contain the most fat contain the least water. In some meats there is considerable refuse, 25 to 30 per cent. In average meat about 12 per cent of the butcher's weight is refuse and non-edible parts.[44] A pound of average butcher's meat is about one half water, and over 10 per cent waste and refuse, which leaves less than 40 per cent fat and protein. Meat is generally considered to have a high nutritive value, due to the comparatively large amounts of fat and protein. Beef contains more protein than any vegetable food, except the legumes, and from 1 to 1.5 per cent mineral matter, exclusive of bone. Some of the mineral matter is chemically united with the protein and other compounds. While figures are given for average composition of beef, it is to be noted that wide variations are frequently to be met with, some samples containing a much larger amount of waste and trimmings than others, and this influences the percent of the nutritive substances. In making calculations of nutrients consumed, as in dietary studies, the figures for average composition of meat should be used only in cases where the samples do not contain an excess either of fat or trimmings.[45] When very lean, there is often a large amount of refuse, and the meat contains less dry matter and is of poorer flavor than from animals in prime condition. In the case of very fat animals, a large amount of waste results, and the flavor is sometimes impaired.

130. Veal differs from beef in containing a smaller amount of dry matter, richer in protein, but poorer in fat. Animals differ in composition at different stages of growth in much the same way as plants. In the earlier stages protein predominates in the plant tissue, while later the carbohydrates are added in larger amounts, reducing the percentage content of protein. In animals the same is noticeable. Young animals are, pound for pound, richer in protein than old animals. While in the case of vegetables the increase in size, or rotundity, is due to starch and carbohydrates, in animals it is due to the addition of fat. But plants, like animals, observe the same general laws as to changes in composition at different stages of growth.

131. Mutton.—There is about the same amount of refuse matter in mutton as in beef. In a side of mutton about 19 percent: are trimmings and waste, and in a side of beef 18.5 per cent. Mutton, as a rule, contains a little more fat and dry matter than beef, and somewhat less protein. A side of beef, as purchased, contains about 50 per cent of water, 14.5 per cent protein, and 16.8 per cent of fat, while a side of mutton, as purchased, contains 42.9 per cent water, 12.5 per cent protein, and 24.7 per cent fat. A pound of beef yields a smaller number of calories by 25 per cent than a pound of mutton. At the same price per pound more nutrients can be purchased as mutton than as beef. The differences in composition between lamb and mutton are similar to those between veal and beef; viz. a larger amount of water and protein and a smaller amount of fat in the same weight of the young animals. Differences in composition between the various cuts of lamb are noticeable. The leg contains the least fat and the most protein, while the chuck is richest in fat and poorest in protein. As in the case of beef, many of the cheaper cuts contain as much or more nutrients than the more expensive cuts. They are not, however, as palatable and differ as to toughness and other physical characteristics.

132. Pork is characterized by a high per cent of fat and a comparatively low per cent of protein. It is generally richest in fat of any of the meats. The per cent of water varies with the fatness of the animal; in very fat animals there is a smaller amount, while lean animals contain more. In lean salt pork there is about 20 per cent water, and in fat salt pork about 7 per cent. There is less refuse and waste in pork than in either beef or mutton. Ham contains from 14 to 15 per cent of refuse, and bacon about 7 per cent. Bacon has nearly twice as much fat and a smaller amount of protein than ham. A pound of bacon, as purchased, will yield nearly twice as much energy or fuel value as a pound of ham. Digestion experiments show that bacon is quite readily and completely digested and is often a cheaper source of fat and protein than other meats. There is about three times as much fat in bacon as in beef. When prepared for the table bacon contains, from 40 to 50 per cent of fat. A pound of high grade, lean bacon furnishes from 0.1 to 0.3 of a pound of digestible protein and from 0.4 to 0.6 of a pound of digestible fat, which is about two thirds as much fat as is found in butter. Bacon contains nearly as much digestible protein as other meats and from two to three times as much fat, making it, at the same price per pound, a cheaper food than other meats. In salt pork there is from 60 to 85 per cent of fat, and less protein than in bacon. The protein and fat of pork differ from those in beef not only in percentage amounts, but also in the nature of the individual proteins and fats. The composition of pork varies with the nature of the food that is consumed by the animal. Experiments show that it is possible by judicious feeding in the early stages of growth to produce pork with the maximum of lean meat and the minimum of fat. After the animal has passed a certain period, it is not possible by feeding to materially influence the percentage of nutrients in the meat. The flavor, too, of pork, as of other meats, is dependent largely upon the nature of the food the animal consumes. When there is a scant amount of available protein in the ration, the meat is dry, nearly tasteless, and contains less of the soluble nitrogenous compounds which impart flavor and individuality.

133. Lard is prepared from the fat of swine, and is separated from associated tissue by the action of heat. A large amount of fat is found lining the back of the abdominal cavity, and this is known as leaf lard. Slight differences are noticeable in the composition and quality of lard made from different parts of the hog. Leaf lard is usually considered the best. Lard is composed of the three fats, olein, stearin, and palmatin, and has a number of characteristic physical properties, as specific gravity, melting point, iodine absorption number, as well as behavior with various reagents, and these enable the mixing of other fats with lard to be readily detected. Lard is used in the preparation of oleomargarine, and it is also combined with various vegetable oils, as cotton-seed oil, in the making of imitation or compound lards.[46] Lard substitutes differ little in general composition from pure lard, except in the structure of the crystals and the percentage of the various individual fats.

134. Texture and Toughness of Meats.—In discussing the texture of meats, Professor Woods states:[45]

"Whether meats are tough or tender depends upon two things: the character of the walls of the muscle tubes and the character of the connective tissues which bind the tubes and muscles together. In young and well-nourished animals the tube walls are thin and delicate, and the connective tissue is small in amount. As the animals grow older or are made to work (and this is particularly true in the case of poorly nourished animals), the walls of the muscle tubes and the connective tissues become thick and hard. This is the reason why the flesh of young, well-fed animals is tender and easily masticated, while the flesh of old, hard-worked, or poorly fed animals is often so tough that prolonged boiling or roasting seems to have but little effect on it.

"After slaughtering, meats undergo marked changes in texture. These changes can be grouped under three classes or stages. In the first stage, when the meat is just slaughtered, the flesh is soft, juicy, and quite tender. In the next stage the flesh stiffens and the meat becomes hard and tough. This condition is known as rigor mortis, and continues until the third stage, when the first changes of decomposition set in. In hot climates the meat is commonly eaten in either the first or second stage. In cold climates it is seldom eaten before the second stage, and generally, in order to lessen the toughness, it is allowed to enter the third stage, when it becomes soft and tender, and acquires added flavor. The softening is due in part to the formation of lactic acid, which acts upon the connective tissue. The same effect may be produced, though more rapidly, by macerating the meat with weak vinegar. Meat is sometimes made tender by cutting the flesh into thin slices and pounding it across the cut ends until the fibers are broken."

135. Influence of Cooking upon the Composition of Meats.[47]—It is believed by many that losses are prevented and the nutritive value conserved when, in the cooking of meat, it is placed directly into boiling water rather than into cold water and then brought to the boiling point and cooked. Extensive experiments have been made by Dr. Grindley in regard to this and other points connected with the cooking of meats, and in general it was found that the temperature of the water in which the meat was placed made little difference in its nutritive value or the amount of material extracted. It was found that by both methods there was dissolved 2.3 percent of the protein matter, 1 percent of the nitrogenous extractives, 1.6 per cent of non-nitrogenous material, and 0.8 per cent of ash, of the raw meat, which was equivalent to about 13 per cent of the total proteid material and 81 percent of the ash. The cold water extract contained bodies coagulated by heat. Cold water did not extract any of the fat, but during the process of cooking, appreciable amounts were lost mechanically. Cooked meats were found to be less soluble in cold water than raw meats. During the process of boiling, meat shrinks in weight about 40 or 45 per cent, depending mainly upon the size of the pieces and the content of fat. The loss in weight is practically a loss of water, and the loss of nutrients, all told, amounts to about 4 per cent, or more, depending upon the mechanical loss.[48] But slight differences were found in the composition of the meats cooked three and five hour periods.

"Careful study in this laboratory has shown that when meat is cooked in water at 80 deg. to 85 deg. C., placing meat in hot or cold water at the start has little effect on the amount of nutrients in the meat which passes into the broth. The meat was in the form of cubes, one to two inches, and in pieces weighing from one to two pounds.

"It is commonly supposed that when meat is plunged into boiling water, the albumin coagulates and forms a crust, which prevents the escape of nutritive materials into the broth. It is also believed that if a rich broth is desired, to be used either as a soup or with the meat as a stew, it is more desirable to place the meat in cold water at the start. From the results of these experiments, however, it is evident that, under these conditions, there can be little advantage in using hot or cold water at the beginning. When meats were cooked by dry heat, as in roasting, a larger amount of nutrients was rendered soluble in water than during boiling. The losses of nutrients were much smaller when meats were cooked by dry heat than when cooked in water, being on the average, water 35 per cent, nitrogenous extractives 9 per cent, non-nitrogenous extractives 17 per cent, fat 7 per cent, ash 12 per cent, and a small loss of protein."

The nutrients in the broth of the meat started in hot water amounted to about 1 per cent of protein, 1 per cent of fat, and O.5 per cent of ash, the amount of nutrients being directly proportional to the length of time and temperature of the cooking. In general, the larger the pieces, the smaller the losses. Beef that has been used in the preparation of beef tea loses its extractive materials, which impart taste and flavor, but there is only a small loss of actual nutritive value. Clear meat broth contains little nutriment—less than unfiltered broth. Most of the nitrogenous material of the broth is in the form of creatin, sarkin, and xanthin, nitrogenous extractives or amid substances having a much lower food value than proteids. Experiments show that some of these extractives have physiological properties slightly stimulating in their action, and it is believed the stimulating effect of a meat diet is in part due to these.[49] They are valuable principally for imparting taste and flavor, and cannot be regarded as nutrients. The variations in taste and flavor of meats from different sources are due largely to differences in extractive material.

"In general, the various methods of cooking materially modify the appearance, texture, and flavor of meat, and hence its palatability, but have little effect on total nutritive value. Whether it be cooked in hot water, as in boiling or stewing, or by dry heat, as in roasting, broiling, or frying, meat of all kinds has a high food value, when judged by the kind and amount of nutrient ingredients which are present." [50]

Beef extracts of commerce contain about 50 per cent of extractive matters, as amids, together with smaller amounts of soluble proteids; ash, mainly added salt, is also present in liberal amounts (20 per cent). Beef extracts have condimental value imparting taste and flavor, which make them useful for soup stocks, but they furnish little in the way of nutritive substance.

136. Miscellaneous Meat Products.—By combining different parts of the same animal, or different meats, a large number of products known as sausage are made. These vary in composition with the ingredients used. In general, they are richer in fat than beef and contain about the same amount of protein. Potato flour and flour from cereals are sometimes used in their preparations, but the presence of any material amount, unless so stated on the package, is considered an adulterant.

Pickled meats are prepared by the use of condiments, as salt, sugar, vinegar, and saltpeter. During the smoking and curing of meats, no appreciable losses of nutrients occur.[51] The smoke acts as a preservative, and imparts condimental properties. Saltpeter (potassium nitrate) has been used from earliest times in the preparation of meats; it preserves color and delays fermentation changes. When used in moderate amounts it cannot be regarded as a preservative or injurious to health. Excessive amounts, however, are objectionable. Smoked meats, prepared with or without saltpeter, give appreciable reactions for nitrites, compounds formed during combustion of the wood by which the meat was smoked. Many vegetables contain naturally much larger amounts of nitrates, taken from the soil as food, than meat that has been preserved with saltpeter.[52]

137. Poultry.—The refuse and waste from chickens, as purchased on the market, ranges from 15 to 30 per cent. The fat content is much lower than in turkeys or ducks, the largest amount being found in geese. The edible portion of all fowls is rich in protein, particularly the dark meat, and the food value is about equal to that of meat in general. When it is desired to secure a large amount of protein with but little fat, chicken supplies this, perhaps, better than any other animal food. A difference is observed in the composition of the meat of young and old fowls similar to that between beef and veal. The physical composition and, to a slight extent, the solubility of the proteids are altered by prolonged cold storage, the difference being noticeable mainly in the appearance of the connective tissue of the muscles. In discussing poultry as food, Langworthy states:[53]

"A good, fresh bird shows a well-rounded form, with neat, compact legs, and no sharp, bony angles on the breast, indicating a lack of tender white meat. The skin should be a clear color (yellow being preferred in the American market) and free from blotches and pin feathers; if it looks tight and drawn, the bird has probably been scalded before being plucked. The flesh should be neither flabby nor stiff, but should give evenly and gently when pressed by the finger."

138. Fish.—From 30 to 60 per cent of the weight of fresh fish is refuse. The edible portion contains from 35 to 50 per cent, and in some cases more, of water. The dry matter is rich in protein; richer than many meats. The nutrients in fish range between comparatively wide limits, the protein in some cases being as low as 6 per cent, in flounder, and in others as high as 30 per cent, in dried codfish. The amount of fat, except in a few cases, as salmon and trout, is small. Salmon is the richest in fat of any of the fishes. When salted and preserved, the proportion of water is lessened and that of the nutrients is increased. Fish can take the place of meat in the dietary, but it is necessary to add a larger amount of fat to the ration because of the deficiency of most fish in this ingredient. Fish has about the same digestibility as meats. It is believed by many to be valuable because it supplies a large amount of available phosphates. Analyses, however, show that the flesh of fish contains no more phosphorus compounds than meats in general, and its food value is due to protein rather than to phosphates.[54]

Fish appears to be as completely and easily digested as meats. Differences in flavor, taste, and palatability are due to small amounts of flavors and extractive materials, varying according to the food consumed by the fish and the conditions under which they lived. The flesh of fish decays more readily than that of other meats and produces ptomaines, or toxic substances, which are the result of fermentation changes usually associated with putrefaction. Cases of poisoning from eating unsound fish are not infrequent.[55]

Shellfish have about the same general composition as fish. In clams there is a larger amount of dry matter than in oysters, which contain about 12 per cent, half of which is protein. When placed in fresh water, the oyster increases in size and undergoes the process known as "fattening." Oftentimes impure water is used for this purpose, which makes the eating of raw oysters a questionable practice from a sanitary point of view, as the water in which they are floated often contains disease-producing germs, as typhoid. During the process of fattening, although the oyster increases in size and weight, it decreases in percentage of nutrients. In discussing the composition of oysters, Atwater states:[7]

"They come nearer to milk than almost any other food material as regards both the amounts and relative proportions of nutrients."

139. Eggs, General Composition.—Eggs are a type of concentrated nitrogenous food. About 75 per cent (shell removed) is water, about one third is yolk, and a little over 50 per cent is albumin or white. The shell makes up from 10 to 12 per cent of the weight. The yolk and white differ widely in composition. The yolk contains a much larger per cent of solids than the white, and is rich in both fat and protein, from a third to a half of the weight being fat. The white has about the same amount of water, 88 per cent, as average milk, but, unlike milk, the dry matter is mainly albumin. The entire egg (edible portion) contains about equal parts of fat and protein; 12 to 13 per cent of each and an appreciably large amount of ash or mineral matter,—from 0.8 to 1 per cent, consisting mainly of phosphates associated with the albumin. There is no material difference in chemical composition between white and dark shelled eggs, or between eggs with different colored yolks. It is simply a question of coloring matter. The egg is influenced to an appreciable extent by feed and general care of the fowls. The egg and the potato contain about the same amount of water. They are, however, distinct types of food, the potato being largely composed of carbohydrates and the egg of protein and fat. Eggs resemble meat somewhat in general composition, although they contain rather less of protein and fat. When eggs are boiled there is a loss of weight due to elimination of water; otherwise the composition is unaltered, the coagulation of the albumin, as stated in Chapter I, consisting simply in a rearrangement of the atoms of the molecule. The egg is particularly valuable in the dietary of the convalescent, when it is desired to secure the maximum amount of phosphorus in organic combination.

The flavor of eggs is in part due to the food supplied to the fowls, as well as the age of the egg. Experiments show that onions and some other vegetables, when fed to fowls, impart odors and taste to the eggs. The keeping qualities of eggs are also dependent upon the food supplied. In experiments at the Cornell Experiment Station, when hens were fed on a narrow, nitrogenous ration, a large number of eggs were produced containing the minimum amount of solid matter and of poor keeping quality, while a larger sized egg of better keeping quality was obtained when a variety of foods, nitrogenous and non-nitrogenous, was supplied.

140. Digestibility of Eggs.—Digestion experiments show that there is but little difference in the digestibility of eggs cooked in different ways. A noticeable difference, however, is observed in the rapidity with which the albumin and proteids are dissolved in a pepsin solution. In general, it was found that, when the albumin was coagulated at a temperature of 180 deg., it was more rapidly and completely dissolved in the pepsin than when coagulated at a temperature of 212 deg. When eggs were cooked at a temperature of 212 deg., the hard-boiled eggs appeared to be slightly more digestible than the soft-boiled eggs, but the digestion was not as complete as when the cooking was done at a temperature of 180 deg.; then no difference in digestibility was found between eggs cooked for a short or a long time. The egg is one of the most completely digested of all foods, practically all the protein and fat being absorbed and available to the body. Langworthy, in discussing Jorissenne's investigations on the digestibility of eggs, states:[53]

"The yolk of raw, soft-boiled, and hard-boiled eggs is equally digestible. The white of soft-boiled eggs, being semi-liquid, offers little more resistance to the digestive juices than raw white. The white of a hard-boiled egg is not generally very thoroughly masticated. Unless finely divided, it offers more resistance to the digestive juices than the fluid or semi-fluid white, and undigested particles may remain in the digestive tract many days and decompose. From this deduction it is obvious that thorough mastication is a matter of importance. Provided mastication is thorough, marked differences in the completeness of digestion of the three sorts of eggs, in the opinion of the writer cited, will not be found."

141. Use of Eggs in the Dietary.—When eggs are at the same price per dozen as meat is per pound, they furnish a larger amount of nutrients. In general, a dozen eggs have a little higher food value than a pound of meat. Eggs are usually a cheaper source of food because a smaller amount is served than of meat. When eggs are 25 cents per dozen, the cost of ten eggs for a family of five is less than that of a pound or a pound and a quarter of beef at 22 cents per pound. The meat, however, would furnish the larger amount of nutrients. Eggs are valuable, too, in the dietary because they are frequently combined with flour, cereal products, and vegetables, which contain a large amount of starch, and some of which contain small amounts of protein. This combination furnishes a balanced ration, as well as secures palatability and good mechanical combination of the foods. Eggs in combination with flour, sugar, butter, and other materials have equally as great a value as when used alone and as a substitute for meat.

Eggs vary in weight from 17.5 to 28 ounces, and more per dozen. They should be purchased and sold by weight. When stored, eggs lose weight. The egg cannot be considered as entirely germ proof, and care is necessary in its handling and use, the same as with other food articles. The cause of the spoiling of eggs is due largely to exterior bacterial infection.


142. General Composition.—Canned meats differ but little in composition from fresh meats. Usually during the process of cooking and canning there is a slight increase in the amount of dry matter, but the relative proportion of protein and fat is about the same as in fresh meat. It is frequently stated that the less salable parts are used in the preparation of canned meats, as it is possible by cooking and the addition of condiments to conceal the inferior physical properties. As to the accuracy of these statements, the author is unable to say. The shrinkage or loss in weight during canning amounts to from 30 to 40 per cent. The liquids in which the cooking and parboiling are done are sometimes used in the preparation of beef extracts. Salt, saltpeter, and condiments are generally added during the canning process. Saltpeter is used, as it assists in retaining the natural color and prevents some objectionable fermentation changes. In moderate amounts it is not generally considered an adulterant. An extensive examination by Wiley and Bigelow of packing-house products and preserved meats showed that of the latter only a small amount contained objectionable preservatives. The authors, after an extended investigation, reported favorably upon their composition and sanitary value, saying they found "so little to criticise and so much to commend in these necessary products." In this bulletin they do not classify saltpeter as an adulterant.[51]

Where fresh meats cannot be secured, canned meats are often indispensable. Usually the nutrients of canned meats cost more than those of fresh meats, and in their use as food much care should be exercised to prevent contamination after opening the cans. Occasionally the meat contains ferment materials that have not been entirely destroyed during cooking, and these, when the cans are stored in warm places, develop and cause deleterious changes to occur. Consequently canned meats should be stored at a low temperature. By recent congressional act, these preparations are now made under the supervision of government inspectors. All diseased animals are rejected, and the sanitary conditions under which the meat is prepared have been greatly improved. Formerly, the most frequent forms of adulteration were substitution of one meat for another, as the mixing of veal with chicken, and the use of preservatives, as borax and sulphites. While the cost of the nutrients in canned meats is generally much higher than in fresh meats, the latter are not always easily obtained, or capable of being kept for any length of time, and hence canned meats are often indispensable.



143. Preparation and Cost of Cereals.—The grains used in the preparation of cereal foods are wheat, oats, corn, rice, and, to a less extent, barley and rye. For some of these the entire cleaned grain is ground or pulverized, while for others the bran and germ are first removed. In order to improve their keeping qualities, they are often sterilized before being put up in sealed packages. Special treatment, as steaming or malting, is sometimes given to impart palatability and to lessen the time required for cooking. As a class, the cereal foods are clean, nutritious, and free from adulteration. Extravagant claims are sometimes made as to their food value, and frequently excessive prices are charged, out of proportion to the cost of the nutrients in the raw material. Within recent years the number of cereal preparations has greatly increased, due to improvements and variations in the methods of manufacture.[56]

Cereal foods are less expensive than meats and the various animal food products. They contain no refuse, are easily prepared for the table, and may be kept without appreciable deterioration. Some of the ready—to-eat brands are cooked, dried, and crushed, and sugar, glucose, salt, and various condimental materials added to impart taste. Others contain malt, or are subjected to a malting or germinating process to develop the soluble carbohydrates, and such foods are sometimes called predigested. It is believed that the cereals are being more extensively used in the dietary, which is desirable both from an economic and a nutritive point of view. Special care is necessary in the cooking and preparation of cereals for the table, in order to develop flavor and bring about hydration and rupturing of the tissues, as explained in Chapter II.

144. Corn Preparations.—Corn or maize is characterized by a high percent of fat and starch, and, compared with wheat and oats, a low content of protein.[57] Removal of the bran and germ lessens the per cent of fat. The germ is removed principally because it imparts poor keeping qualities. Many of the corn breakfast foods contain 1 per cent or less of fat and from 8 to 9 per cent of protein. Coarsely ground corn foods are not as completely digested and assimilated as those more finely ground. As in the case of wheat products, the presence of the bran and germ appears to prevent the more complete absorption of the nutrients. Finely ground corn meal compares favorably in digestibility with wheat flour. Corn flour is prepared by removal of the bran and germ and granulation of the more starchy portions of the kernel, and has better keeping qualities than corn meal from which the bran and germ have not been so completely removed. At times corn flour has been sufficiently low in price to permit its use for the adulteration of wheat flour. The mixing of corn and wheat flours, however, is prohibited by law unless the product is so labeled. When combined with wheat flour, corn bread and various other articles of food are prepared, but used alone corn flour is not suitable for bread making, because its gluten lacks the binding properties imparted to wheat flour by the gliadin. It is essential that corn be used with foods of high protein content so as to make a balanced ration; for when it forms a large part of the dietary, the ration is apt to be deficient in protein. In a mixed dietary, corn is one of the cheapest and best cereals that can be used. Too frequently, however, excessive prices are charged for corn preparations that contain no more nutrients than ordinary corn meal. There is no difference between yellow and white corn meal so far as nutritive value is concerned.

145. Oat Preparations are characterized by large amounts of both protein and fat. Because of the removal of the hulls, they contain more protein than the original grain. The oat preparations differ little in chemical composition. They all have about 16 per cent of protein, 7 per cent of fat, and 65 per cent of starch, and are richer in ash or mineral matter than other cereals. The main difference is in method of preparation and mechanical composition. Some are partially cooked and then dried. Those costing 7 cents or more per pound do not contain any greater amount of nutritive substance than those purchased in bulk at about half the price. At one time it was believed that oats contained a special alkaloid having a stimulating effect when fed to animals. Recent investigations, however, show that there is no alkaloidal material in oats, and whatever stimulating effect they may have results from the nutrients they contain. Occasionally there is an appreciable amount of cellulose, or fiber, left in the oat preparations, due to imperfect milling. This noticeably lowers the digestibility. Oatmeal requires much longer and more thorough cooking than many other cereals, and it is frequently used as food when not well prepared. Digestion experiments show that when oatmeal is cooked for four hours or more, it is more readily acted upon by the diastase ferment and digested in a shorter time than oatmeal cooked only a half hour.[5] Oatmeal is one of the cheapest sources from which protein is obtained, and when well cooked it can advantageously form an essential part of the ration. Unless thoroughly cooked, the oat preparations do not appear to be quite so completely or easily digested as some of the other cereals.

146. Wheat Preparations differ in chemical composition more than those from oats or corn, because wheat is prepared in a greater variety of ways. They are made either from the entire kernel, including the bran and germ, or from special parts, as the granular middlings, as in the case of some of the breakfast foods, and a few are made into a dough and baked, then dried and toasted. Some special flours are advertised as composed largely of gluten, but only those that have been prepared by washing out the starch are entitled to be classed as gluten flours.[58] For the food of persons suffering from diabetes mellitus physicians advise the use of flour low in starch, and this can be made by washing and thus removing a portion of the starch from wheat flour, as directed in Experiment No. 30. The glutinous residue is then used for preparing articles of food. Analyses of some of the so-called gluten flours show that they contain no more gluten than ordinary flour, particularly the low grades. A number of wheat breakfast foods are prepared by sterilizing the flour middlings obtained after removal of the bran and germ. These middlings are the same stock or material from which the patent grades of flour are made, and they differ from wheat flour only in mechanical structure and size of the particles. Where granular wheat middlings can be secured in bulk at the same price as flour they furnish a valuable and cheap cereal breakfast food.

As to the digestibility and food value, the wheat breakfast foods have practically the same as graham, entire wheat, or ordinary patent flour, depending upon the stock which they contain. Those with large amounts of bran and germ are not as completely digested as when these parts of the kernel are not included. Wheat preparations, next to oats, have the most protein of any of the cereal foods. Occasionally they are prepared from wheats low in gluten and not suitable for bread-making purposes. When purchased in bulk the wheat preparations are among the cheapest foods that can be used in the dietary.[56]

147. Barley Preparations are not so extensively used as wheat, oats, and corn. Barley contains a little more protein than corn, but not quite so much as wheat; otherwise it is quite similar to wheat in general composition. Sometimes in the preparation of breakfast foods barley meal is mixed with wheat or corn. Barley is supposed to be more readily digested than some of the other cereals, because of the presence of larger amounts of active ferment bodies, and it is frequently used for making an extract known as "barley water," which, although it contains very little nutritive value, as less than one per cent of the weight of the barley is rendered soluble, is useful in its soothing influence and mechanical action upon the mucous membrane of the digestive tract.

148. Rice Preparations.—Rice varies somewhat in composition, but usually contains a slightly lower percentage of protein than corn and also a smaller amount of fat. It is particularly rich in starch, and has the least ash or mineral matter of any of the cereals. In order to make a balanced ration, rice should be supplemented with legumes and other foods rich in proteids. It is a valuable grain, but when used alone it is deficient in protein. Rice is digested with moderate ease, but is not as completely absorbed by the body as other cereals, particularly those prepared by fine grinding or pulverization. Of late years rice culture has been extensively introduced into some of the southern states, and the domestic rice seems to have slightly higher protein content than the imported. Rice contains less protein than other cereals, and the starch grain is of different construction. Rice does not require such prolonged cooking as oatmeal; it needs, however, to be thoroughly cooked.

149. Predigested Foods.[56]

"It is questionable whether it would be of advantage to a healthy person to have his food artificially digested. The body under normal conditions is well adapted to utilize such foods as the ordinary mixed diet provides, among them the carbohydrates from the cereals. Moreover, it is generally believed that for the digestive organs, as for all others of the body, the amount of exercise they are normally fitted to perform is an advantage rather than the reverse. It has been said that 'a well man has no more need of predigested food than a sound man has for crutches.' If the digestive organs are out of order, it may be well to save them work, but troubles of digestion are often very complicated affairs, and the average person rarely has the knowledge needed to prescribe for himself. In general, those who are well should do their own work of digestion, and those who are ill should consult a competent physician."—WOODS AND SNYDER.

Previous Part     1  2  3  4  5  6     Next Part
Home - Random Browse