The object of all cooking is to make the food-stuffs more palatable or more digestible, or both combined. In general, the starchy foods are rendered more digestible by cooking; the albuminous and fatty foods less digestible. The appetite of civilized man craves and custom encourages the putting together of raw materials of such diverse chemical composition that the processes of cooking are also made complex.

Bread - the staff of life - requires a high degree of heat to kill the plant-life, and long baking to prepare the starch for solution; while, by the same process, the gluten is made less soluble. Fats, alone, are easily digested, but in the ordinary method of frying, they not only may become decomposed themselves, and therefore injurious ; but they also prevent the necessary action of heat, or of the digestive ferments upon the starchy materials with which the fats are mixed.

The effects of cooking upon the solubility of the three important food-principles may be broadly stated thus:

Starchy foods are made more soluble by long cooking at moderate temperatures or by heat high enough to change a portion of the starch to dextrine, as in the brown crust of bread.

Nitrogenous foods. The animal and vegetable albumins are made less soluble by heat; the gelatinoids more soluble.

Fats are readily absorbed in their natural condition, but are decomposed at very high temperatures and their products become irritants.