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Food Values and Adulterations: Water

Water occurs in varying percentages in nearly all foods, even those which we are accustomed to think of as entirely dry, such as wheat and other dry grains, or dried peas and beans.

Common examples of fat are lard, suet, butter and olive oil. The ash in foods consists of various kinds of mineral matter which are left as a residue when the foods are burned.

The only kind of mineral matter usually added to foods in cookery is common salt.

In addition to these five kinds of nutrients, there is another class of substances in food which is of some value in cookery, although it is not believed that they furnish fuel or contribute to the growth of bodily tissue. They are called "extractives." They include various volatile oils and similar flavors which are "extracted" from foods in the process of cookery, whence the name. They give to certain foods the characteristic taste and odor which "make the mouth water." They aid digestion by stimulating the palate and promoting the flow of the saliva, gastric juice and other secretions which are necessary to good digestion. An example is the well known meat extract used for bouillon. This is not a food but merely an appetizing condiment.

Interest in the subject of food values centers in the three classes of nutrients-proteid, carbohydrate, and fat. Water is plentiful in every diet and is usually taken freely to satisfy thirst. Ash or mineral matter represents only about 1 per cent of most foods and is thought to be abundant in the ordinary diet. It is most plentiful in the natural food of the young, as in milk and eggs, and is of special importance to furnish material for bony structures during the period of growth and also in some diseased conditions. The housekeeper's problem is thus narrowed to the supply of sufficient proteid, carbohydrate and fat in the right proportions, as cheaply as possible, and in readily available, that is easily digestible, forms.

Uses of Nutrients in the Body.- The three principal classes of nutrients-proteid, fat and carbohydrate, all serve as fuel to yield energy in the forms of heat and muscular power. But the chief source of fuel is fat. Hence the Eskimo eats freely of tallow and blubber to keep up the bodily heat in winter. Any excess of fat may be stored in the body against future needs. Thus the bear lives on his fat during his long winter's sleep, and comes out lean in the spring. The carbohydrates-sugar and starch-may be immediately consumed as fuel, or they may be converted into and stored as fat.

The proteids may also be consumed as fuel. But this does not ordinarily happen unless there is a deficiency of fat and carbohydrate in the diet.

The normal use of proteid is in the growth and repair of the bodily tissues. The importance of this class of nutrients in food is due to the fact that none of the others can take its place. This explains why an infant fed wholly on condensed milk -which is rich in sugar and fat, but deficient in proteid (curds), may be fat but not strong. Roughly speaking, fat and carbohydrate supply heat and energy, and proteid forms tissue. This broad distinction is very serviceable and should be kept clearly in mind.