Human Foods and Their Nutritive Value Part 4

84. General Composition of Legumes.--Peas, beans, lentils, and peanuts are the legumes most generally used for human food. As a cla.s.s, 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 subst.i.tute 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.

[Ill.u.s.tration: FIG. 19.--GRAPHIC COMPOSITION OF BEANS.

HACKED PART INDIGESTIBLE.]

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

[Ill.u.s.tration: FIG. 20.--BEANS, RAW AND COOKED. SKINS, WET AND DRY.]

87. Use of Beans in the Dietary.--There is no vegetable food capable of furnis.h.i.+ng 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 quant.i.ty 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.

[Ill.u.s.tration: FIG. 21.--PEA STARCH GRANULES.]

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

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

NUTS

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

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

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

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

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

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

"The small, green, and immature nuts are grated fine for medicinal use, and when mixed with the oil of the ripe nut it becomes a healing ointment. The jelly which lines the sh.e.l.l 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 b.u.t.ter 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 subst.i.tute for oleomargarine."

98. Use of Nuts in the Dietary.--When nuts can be secured at a low price per pound, ten cents or less, they compare favorably in nutritive value with other staple foods. Digestion experiments with rations composed largely of nuts show that they are quite thoroughly digested.

Professor Jaffa of the California Experiment Station, in discussing the nutritive value of nuts and fruits, says:[35]

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

AVERAGE COMPOSITION OF NUTS

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

=========================================================================== |REFUSE|EDIBLE | EDIBLE PORTION |VALUE[A]

| | |------------------------------| | |PORTION|Water|Prot.| Fat |Carb.| Ash | PER LB.

--------------------------------------------------------------------------- | % | % | % | % | % | % | % |Calories Almonds | 64.8 | 35.2 | 1.7 | 7.3 |19.3 | 6.2 | 0.7 | 1065 Almonds, kernels | -- | 100.0 | 4.8 |21.0 |54.9 |17.3 | 2.0 | 3030 Brazil nuts | 49.6 | 50.4 | 2.7 | 8.6 |33.6 | 3.5 | 2.0 | 1545 Filberts | 52.1 | 47.9 | 1.8 | 7.5 |31.3 | 6.2 | 1.1 | 1575 Filberts, kernels | -- | 100.0 | 3.7 |15.6 |65.3 |13.0 | 2.4 | 3290 Hickory nuts | 62.2 | 37.8 | 1.4 | 5.8 |25.5 | 4.3 | 0.8 | 1265 Pecans | 49.7 | 50.3 | 1.4 | 5.2 |35.6 | 7.2 | 0.8 | 1733 Pecans, kernels | -- | 100.0 | 2.9 |10.3 |70.8 |14.3 | 1.7 | 3445 Walnuts | 58.0 | 42.0 | 1.2 | 7.0 |27.0 | 6.1 | 0.7 | 1385 Walnuts, kernels | -- | 100.0 | 2.8 |16.7 |64.4 |14.8 | 1.3 | 3305 Chestnuts | 16.1 | 83.9 |31.0 | 5.7 | 6.7 |39.0 | 1.5 | 1115 Acorns | 35.6 | 64.4 | 2.6 | 5.2 |24.1 |30.9 | 1.6 | 1690 Beechnuts | 40.8 | 59.2 | 2.3 |13.0 |34.0 | 7.8 | 2.1 | 1820 b.u.t.ternuts | 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 Sh.e.l.led peanuts | -- | 100.0 | 1.6 |30.5 |49.2 |16.2 | 2.5 | 2955 Peanut b.u.t.ter | -- | -- | 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 a.n.a.lyses.]

[Footnote B: Including salt, 4.1.]

CHAPTER VII

MILK AND DAIRY PRODUCTS

99. Importance in the Dietary.--There is no article of food which enters so extensively into the dietary as milk, and it is one of the few foods which supply all the nutrients,--fats, carbohydrates, and proteids.[36] Milk alone is capable of sustaining life for comparatively long periods, and it is the chief article of food during many diseases.

An exclusive milk diet for a healthy adult, however, would be unsatisfactory; in the case of young children, milk is essential, because the digestive tract has not become functionally developed for the digestion of other foods.

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

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

======================= | Per Cent Fat | 3.5 Casein | 3.25 Alb.u.min | 0.50 Milk sugar | 5.00 Ash | 0.75 =======================

[Ill.u.s.tration: FIG. 22.--MILK FAT GLOBULES.]

Fat is the most variable const.i.tuent 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 alb.u.min, 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 ma.s.ses resistant to the digestive fluids. Barley water and lime water in small amounts are also useful for a.s.sisting mechanically in the digestion of milk. Milk at ordinary prices is one of the cheapest foods that can be used.

[Ill.u.s.tration: FIG. 23.--DIRT IN A SAMPLE OF UNSANITARY MILK.]

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

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

104. Pasteurized Milk.--In order to destroy the activity of the bacterial organisms, milk is subjected to a temperature of 157 F. for ten minutes or longer, which process is known as pasteurization. When milk is heated to a temperature above 180, it is sterilized. Below 157, the alb.u.min 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 F. is registered, and the milk is kept at this temperature for about ten minutes. It is then cooled and placed in the refrigerator.

[Ill.u.s.tration: FIG. 24.--PASTEURIZING MILK.]