The nitrogenous and carbohydrate principles are the two with which in cooking we have most to do. Albumen and starch represent these. An egg is almost pure albumen, while a potato is largely starch. When the conditions involved in the cooking of these two articles are well understood, a firm foundation upon which to build the future structure of cookery has been laid.

The Cooking Of Starch

If potatoes be pared and allowed to stand in cold water, some of the starch granules of the potato will settle to the bottom of the dish. These granules will remain to all outward appearance unchanged, even if they stand hours in the water. That is, starch is not soluble in cold water. Solubility and digestibility are practically synonymous terms, for all solid food material needs to become soluble before it can pass through the walls of the digestive system and be assimilated.

Prehistoric man was undoubtedly endowed with strong digestive powers, and was able, to some extent at least, to digest uncooked starch, but civilized man needs all the aid that cookery can devise to render the starch in his food soluble.

Upon the application of heat the wrinkled exterior of the hydrated, or water-soaked, starch granules becomes distended and bursts, and if the granules be stirred during this process their delicate walls are broken down and a pasty mass results, which, when dry, is soluble in either cold or hot water. Such starch is readily digestible.

But starch to be assimilated, must not only be soluble, it must be changed by the ptyalin of the saliva and the gastric juice into sugar, which, as soon as formed, may be absorbed into the circulatory system. This change may be partially brought about outside of the digestive apparatus and at a saving of energy on the part of the digestive organs. Of course, any approximation to this result would be of gain to the individual. This change is produced outside of the human body by subjecting starch to a high degree of heat. If ordinary dry starch granules be heated to a temperature about 400° and kept there some ten minutes, they become brown in color, and, if mixed with water, they form a gummy solution, which does not change color, as does starch, when subjected to the iodine text. These granules are no longer starch, but dextrine; they are now in a condition to be easily changed into sugar and assimilated by the system.

We see, at once, why baked, rather than boiled, potatoes are given to a child or an invalid. A potato boiled in water can attain a temperature no higher than the water in which it is cooked, viz., 212°. So that, though the starch be made soluble, it is not changed, as it is in potato that is baked in an oven at a temperature of nearly 400° Fahr. The same is true in the baking of bread, and this is one reason why bread should be baked in small loaves. The intense heat of the oven changes the starch upon the outside to dextrine, but fails to change the starch throughout the loaf, on account of the large amount of moisture contained in it, which reduces the temperature somewhat.

Then, in cooking starch, long cooking at a moderate temperature, or cooking at a sufficiently High temperature to change a portion of the starch to dextrine is desirable.