The most important carbonaceous food which we use is starch. Most of our starch comes from potatoes and the cereals, such as corn and wheat. Under this head we will discuss, however, those starch foods found in the market as practically pure starch. These starch foods in the order of their importance in the dietary are: Cornstarch, tapioca, sago, arrowroot. Cornstarch is prepared from young maturing corn. In the process of manufacture the proteins and oils and cellulose are completely separated from the starch, and this is collected in a practically pure state, and marketed as a white powder of almost impalpable fineness. Tapioca is derived from the root of a tropical plant, while sago is from the pith of the sago palm. These products are practically pure starch, and are found in the market in granular form. Arrowroot is a similar product, though less extensively used than any of the above. In preparation of these products they absorb a great deal of water and in cooking swell up into a paste or jelly, opalescent, clear, or milky colored. While they represent more or less condensed nourishment, as is the case with sugar, they are quite flavorless and require the admixture of other substances to give them relish. It is very common to mix fruit of some kind with tapioca and sago, and to make a fruit dressing or a cream dressing rather highly flavored with vanilla or lemon to be taken with the various cornstarch preparations.

While these cornstarch preparations are, as a rule, used as desserts, there is no good reason why they might not be used as a principal source of starchy foods. The custom, however, of flavoring them with the fruit or cream dressings and admixtures has, without doubt, determined their location in the menu among the desserts.

The starches are chemically closely allied to the sugars, and in their digestion the complex starch molecules composed of many monosaccharid groups are step by step broken up, first into dextrin, then into maltose, and finally into dextrose. This process begins in the mouth, where the ptyalin of the saliva changes the starch into dextrin and maltose. The maltose, which is a disac-charid (C12H22O11), passes unchanged through the stomach into the small intestine, where the ferment maltose breaks it up into two dextrose molecules. In this form it is absorbed and used in the body for the production of heat and muscular energy in a way exactly as are the monosaccharid molecules derived from the sugar direct.