The application of heat to food is comparatively of recent origin in the evolution of mankind. The use of fire involves a certain amount of mental ingenuity, and could not be practised by man's anthropoid ancestors. Anthropoid animals, whether human or ape, have a great amount of curiosity for the unusual and the new.

Chemical Changes Produced By Cooking

Man probably began his cooking experiments by soaking hard foods in warm water, then in hot water, or by warming cold foods at his camp-fire. As heat volatilizes the pleasant odorous substance present in many foods, the custom of heating them probably became popular. The habit of cooking spread, as many other novel and interesting customs have spread, from this primitive process to the French chef, regardless of whether the results were beneficial or harmful.

The question whether foods should be eaten cooked or uncooked can best be answered by examining the chemical and mechanical changes produced in the process of cooking, and their consequent physiological effects.

Cooking may be divided into two classes, namely, Moist Heat and Dry Heat. To illustrate:

Sugars are not chemically affected by boiling with water, while starch, cooked with boiling water, or steam, absorbs from three to five times its bulk of moisture, and changes into a soft, pasty, or semi-dissolved mass. Under dry heat, sugars are converted into a brown substance, known as caramel, while starch cooked under a temperature of 300° to 400° of dry heat, is changed into a dextrin, of which toast and zwieback are examples.

Effect Of Heat On Sugars

Fats are not changed chemically by moist heat; that is, by being boiled in water, but the globules are melted and the hot fat spreads in a film over other material which may be present. In dry heat, fats are chemically decomposed, forming irritating vapors. The odors of frying fat are due to the presence of small quantities of these decomposition products. In larger quantities, and with greater heat, these substances are exceedingly irritating to the mucous membrane of the stomach and the intestines.

Effect Of Heat On Fats

The chemical changes produced by heating proteids are of much more importance than are those which take place in other foods. Simple proteids, such as albumin and globulin, are coagulated at a temperature of about 160°. This change is familiar in the coagulation of egg whites under low temperature. Other proteids undergo similar changes, governed by the degree and kind of heat (dry or moist), to which they are subjected. This change in proteid material continues with the application of prolonged heat, until the proteid, under dry heat, is converted into a dark brittle mass, wholly insoluble and indigestible.

Effect Of Heat On Proteids

If the student will take the white of an egg, and bake it for some time in an oven, he will observe the coagulation or hardening of the proteid. The chemical nature of this change is one of great complexity. The molecules combine with each other, forming almost indestructible substances. The combined or coagulated forms of proteid are represented in nature by horns, hoofs, finger nails, and hair.

Starch Digestion - Cooked And Uncooked

The student will remember the reference made in Lesson V to experiments concerning the digestibility of starch when taken in various forms. In these experiments, though conducted for the purpose of demonstrating the supposed advantage of excessive cooking, the results showed that at the time the contents of the stomach were removed, all the proteids of the uncooked grain had been digested, while the percentage of proteid digested from the various forms of cooked grain grew less as the cooking was increased. As the chief function of the gastric juice is the digestion of proteids, the real significance of the above experiments was exactly the opposite from that which was intended to be proved.

The statement is frequently made that the starch of grain cannot be digested without cooking, because the cells enclosing the starch grains have indigestible or insoluble cellulose walls. The old theory is that cooking expands the starch and ruptures or tears down these walls, freeing the contents so that the digestive juices may act upon the enclosed starch granules. This is a theory unsupported by facts. The cell walls on the interior of the grain kernel are very filmy, and in the mature grain scarcely exist at all. The analysis of wheat flour shows only a trace of cellulose fiber. Were these cellulose walls within the wheat grain, as this theory commonly teaches, flour would show a liberal quantity of cellulose. The cellulose wall theory, as a necessity for cooking starch, is an excellent illustration of the ease with which a groundless statement or theory may be used to prove or to explain some popular prejudice.

Comparative digestion of cooked and uncooked grain.

In the process of cooking, the tendency is to render the organic salts contained in food entirely inorganic. This change from organic to inorganic salts is measured by the temperature to which the foods are subjected. Many of these salts are combined with the nitrogenous constituents of food, therefore when subjected to certain degrees of heat they are of little value in the construction of the proteid molecules within the body. This is especially true of fresh or green vegetables.

Reasons given for cooking starch.

Excuses For Cooking Our Food

Inasmuch as the majority of people favor cooking, probably forgetting that about half of the food consumed in the world at the present time is taken in its natural or uncooked state, it may be well to mention some of the views advanced by those who believe that the present diet of cooked grain is better for modern man than an elementary diet, and who attempt to give a natural explanation. One theory is that man has subsisted so long upon cooked foods that his organs have become fitted for a cooked diet, and a cooked diet only. Another view sometimes advanced is, that while cooked foods were originally detrimental, yet by continued use man has become fitted for such a diet and unfitted for a natural diet. These are but other forms of the old belief in the inheritance of acquired characteristics. This belief, however, is steadily losing ground among evolutionists. There is no more reason to believe that a modified function of the stomach would be inherited, than there is to believe that small feet would be inherited among the Chinese women just because these organs are mutilated by local custom.

Ancestral habits not inherited.

The best light of scientific knowledge now leads us to believe that the healthy child of today is, in its capacity for nutrition, essentially like the primitive child, and would thrive best upon a varied diet of natural foods.

Experiment Upon Animals

While I do not claim that the methods of animal feeding apply accurately to man, yet the digestive and the assimilative processes of animals are so closely related to the human processes, that the results obtained in animal nutrition are very instructive to the student of human food science.

About thirty years ago, when the scientific study of agriculture first became prevalent, an experiment was made in cooked food for animals, upon an extensive basis. At that time it was the universal belief that man owed much of his superiority over other animals to the use of cooked food. This argument was put forth with great force and appeared quite reasonable. It was asked whether animals other than man would be benefited by changing to a cooked bill of fare.

During this agitation numerous western farmers put their hogs, chickens, cows, horses, and sheep upon a cooked bill of fare, and many enthusiastic feeders claimed beneficial results. Later the various Governmental Experimental Stations took up the subject and made many careful, complete, and comparative tests of the effects of cooked and uncooked food for animals. The result did not show the expected thing. The cooking experiments in the majority of cases proved injurious, and the general decision of the Government investigators was that cooking food for animals was useless and detrimental to the great live stock industry. Stock food cookery has now become entirely obsolete.

Governmental experiments on cooked food for animals

Man is the only animal that cooks his food, and has made great progress in civilization while subsisting on a cooked diet, but cooking is no more the cause of his advancement than silk hats and swallow-tailed coats. He has advanced only according to the degree that he has thought, studied, and experimented. Cooking has undoubtedly enabled man to utilize many things as food, that he could not and would not have used otherwise, but whether this has aided or retarded in his material progress is yet an unsolved question.

Cooking a habit of civilization