While fruits, nuts, and some vegetables may be and are eaten raw, man has from early times cooked meats and cereals. The cereals were first probably parched among the coals. Primitive peoples barbecued their animals over heaps of coals, or roasted over the coals pieces of flesh cut or torn from the big game. Small animals were roasted, sometimes over the coals, sometimes incased in mud and baked in the hot ashes.

Cooking serves several important purposes; among the most important is the development of pleasing flavors. It is not unlikely that among primitive peoples this was the sole reason for cooking. We recognize now, in the light of modern study, that a further important advantage is gained - namely, the sterilization of the cooked foods, thus killing all parasites and microorganisms. A further important end gained in cooking is to make the food more easily or more completely digestible. The cooking of meat makes the connective tissues more tender and digestible by partially or wholly gelatinizing them, thus making what may have been a tough piece of meat only partially digestible and exceedingly difficult of mastication, easily masticated, pleasing in flavor, and readily and completely digestible. In a similar way cellulose portions of vegetables, fruits, and cereals are broken up and softened, making the food more easily masticated, more pleasing in flavor, and more readily digestible.

Certain principles should govern the cooking of foods.

I. Heat And Moisture Essential

As indicated in the preceding paragraph, the connective tissues of cereals, vegetables, and meats - that is, the cellulose of cereals and vegetables and the collagen of meat - can only be made tender, presentable and palatable by the combined action of heat and moisture for a considerable period of time. The time varies from thirty minutes or an hour in the case of some vegetables, to several hours in the case of other vegetables, and of those meats in which connective tissue makes a large proportion.

II. Extraction Versus Retention

A second fundamental principle to be observed in cooking is that which concerns the juices of the food to be cooked.

To extract these juices as in the preparation of vegetable soups, and meat bouillons, broths, and soups, it is necessary to immerse the material in cold water, bring the substance very slowly to the simmering point, at which point it should be kept for a number of hours. This results in a gradual extraction of the flavors of the food. Various modifications of this general process need not be here described. It is enough to say that the clear soups, broths, and extracts thus prepared, while possessing little nutriment, possess the delicate and delicious flavor of the vegetable or meat and are, therefore, appetizing introductions to a meal. All such clear broths, bouillons, or soups are, however, almost completely lacking in nourishment and exert their influence as a direct stimulation to activities of the gastric glands. Incident to the preparation of these broths, bouillons, and soups, the vegetable or meat "stock" is thoroughly cooked and the cellulose of the vegetable made tender, and the collagen of the connective tissue gelatinized. A very common variation of these preparations is to leave considerable portions of vegetables or meats in the soup, sometimes even adding such other food elements as boiled rice, barley, egg, etc.

Retention of the juices of these foods that are to be subjected to boiling is accomplished by plunging them at once into boiling water. This coagulates the surface proteins which, especially in the case of meat, locks up the juices to a large extent within the body of the meat. In the cooking of meats particularly, retention of the juices is more readily accomplished when the meat is broiled, roasted or baked, as the dry heat of the grill or of the oven when the meat is subjected from the first to high temperature, sears the surface of the meat into a sort of crust which effectually retains the juices.