LEGUMES--PEAS, BEANS AND LENTILS.
These vegetables contain as much protein as meat; yet, this being inferior in quality to that contained in meat, they can scarcely be given a place in the same cla.s.s; therefore we will give them an intermediate position in food value between meat and grains. From the standpoint of economy they occupy a high place in nutritive value, especially for outdoor workers. (See Recipes.)
CHAPTER VI.
Fats and Oils.
Fats and oils contain three elements--carbon, oxygen and hydrogen.
About one-fifth of the body is composed of fat. Before death results from starvation 90 per cent. of the body fat is consumed.
USES OF FAT.
(1) To furnish energy for the development of heat; (2) to supply force; (3) to serve as covering and protection in the body; (4) to lubricate the various structures of the body; and (5) to spare the tissues. The fats and oils used as food all serve the same purpose, and come before the carbohydrates in fuel and force value; in combination with proteids, they form valuable foods for those engaged in severe muscular exercise, such as army marching, mining expeditions, etc.
Fats and oils are but little changed during digestion. The fat is divided into little globules by the action of the pancreatic juice and other digestive elements, and is absorbed by the system. Fat forms the chief material in adipose tissue, a fatty layer lying beneath the skin, which keeps the warmth in the body, and is re-absorbed into the blood, keeping up heat and activity, and preserving other tissues during abstinence from food. Fat sometimes aids the digestion of starchy foods by preventing them from forming lumpy ma.s.ses in the mouth and stomach, hence the value of using b.u.t.ter with bread, potatoes, etc. The animal fats are more nutritive than the vegetable, b.u.t.ter and cream heading the list. Cooking fats at a very high temperature, such as frying, causes a reaction or decomposition, which irritates the mucous membrane and interferes with digestion.
The princ.i.p.al animal fats are b.u.t.ter, cream, lard, suet, the fat of mutton, pork, bacon, beef, fish and cod liver oil. The vegetable fats and oils chiefly used as food are derived from seeds, olives, and nuts. The most important fats and oils for household purposes are:
b.u.t.tER.
b.u.t.ter, which contains from 5 to 10 per cent. of water, 11.7 per cent.
fat, 0.5 per cent. casein, 0.5 per cent. milk sugar (Konig). The addition of salt to b.u.t.ter prevents fermentation. b.u.t.ter will not support life when taken alone, but with other foods is highly nutritious and digestible.
CREAM.
Cream is one of the most wholesome and agreeable forms of fat. It is an excellent subst.i.tute for cod liver oil in tuberculosis. Ice cream when eaten slowly is very nutritious.
LARD.
Lard is hog fat, separated by melting.
SUET.
Suet is beef fat surrounding the kidneys.
COTTOLENE.
Cottolene is a preparation of cotton-seed oil.
OLEOMARGARINE.
Oleomargarine is a preparation of beef fat provided as a subst.i.tute for b.u.t.ter.
OLIVE OIL.
Olive oil is obtained from the fruit, and is considered to be very wholesome; in some cases being preferred to either cod-liver oil or cream for consumptives.
COTTON SEED OIL.
Cotton seed oil is frequently subst.i.tuted for olive oil.
NUTS.
Nuts contain a good deal of oil.
CHAPTER VII.
Carbohydrate Foods.
The idea of starchy foods is usually connected with such substances as laundry starch, cornstarch, arrow root, etc. These are, of course, more concentrated forms of starch than potatoes, rice, etc. Many starchy foods contain other ingredients, and some are especially rich in proteids.
The following table may help to make this clear (At.w.a.ter):--
PERCENTAGE OF STARCH IN VEGETABLE FOODS.
-----------------+----------- | Per Cent.
-----------------+----------- Wheat bread | 55.5 Wheat flour | 75.6 Graham flour | 71.8 Rye flour | 78.7 Buckwheat flour | 77.6 Beans | 57.4 Oatmeal | 68.1 Cornmeal | 71.0 Rice | 79.4 Potatoes | 21.3 Sweet Potatoes | 21.1 Turnips | 6.9 Carrots | 10.1 Cabbage | 6.2 Melons | 2.5 Apples | 14.3 Pears | 16.3 Bananas | 23.3 -----------------+-----------
It is estimated that starch composes one-half of peas, beans, wheat, oats and rye, three-fourths of corn and rice, one-fifth of potatoes.
Vegetable proteids, as already stated, are less easily digested than those belonging to the animal kingdom, therefore it must be remembered that a purely vegetable diet, even though it may be so arranged as to provide the necessary protein, is apt to over-tax the digestive organs more than a mixed diet from both the animal and vegetable kingdoms. Much depends upon the cooking of the starchy foods in order to render them digestible. (Study chapter on Digestion in the Public School Physiology.)
STARCH.
The digestion of starch--which is insoluble in cold water--really begins with the cooking, which by softening the outer coating or fibre of the grains, causes them to swell and burst, thereby preparing them for the chemical change which is caused by the action of the saliva in converting the starch into a species of sugar before it enters the stomach. Substances which are insoluble in cold water cannot be absorbed into the blood, therefore are not of any value as food until they have become changed, and made soluble, which overtaxes the digestive organs and causes trouble. The temperature of the saliva is too low to dissolve the starch fibre unaided. Each of the digestive juices has its own work to do, and the saliva acts directly upon the starchy food; hence the importance of thoroughly masticating such food as bread, potatoes, rice, cereals, etc. The action of heat, in baking, which causes the vapor to rise, and forms the crust of starchy food, produces what is called dextrine, or partially digested starch.
Dextrine is soluble in cold water, hence the ease with which crust and toast--when properly made--are digested. It is more important to thoroughly chew starchy food than meat, as it is mixed with another digestive juice, which acts upon it in the stomach.
Sugars.
SUGAR.
There are many varieties of sugar in common use, viz.: cane sugar, grape sugar or glucose, and sugar of milk (lactose). As food, sugars have practically the same use as starch; sugar, owing to its solubility, taxes the digestive organs very little. Over-indulgence in sugar, however, tends to cause various disorders of a.s.similation and nutrition. Sugar is also very fattening, it is a force producer, and can be used with greater safety by those engaged in active muscular work. Cane sugar is the clarified and crystallized juice of the sugar cane. Nearly half the sugar used in the world comes from sugar cane, the other half from beet roots. The latter is not quite so sweet as the cane sugar. Sugar is also made from the sap of the maple tree, but this is considered more of a luxury; consequently, not generally used for cooking purposes.
MOLa.s.sES AND TREACLE.
Mola.s.ses and treacle are formed in the process of crystallizing and refining sugar. Treacle is the waste drained from moulds used in refining sugar, and usually contains more or less dirt.
GLUCOSE.
Glucose, or grape sugar, is commonly manufactured from starch. It is found in almost all the sweeter varieties of fruit. It is not so desirable for general use as cane sugar.