Wheat is of two principal kinds, characterized as soft and hard wheat, though there are hundreds of named varieties of the grain. The distinction between many of these is due to variation in the relative proportions of starch and nitrogenous matter. Some contain not more than eight per cent of nitrogenous elements, while others contain eighteen or twenty per cent, with a corresponding decrease in carbonaceous elements. This difference depends upon the soil, cultivation, season, climate, and other conditions under which the grain is produced.
The structure of the wheat grain consists of an external tegument of a hard, woody nature, so coherent that it appears in the form of scales or bran when the wheat is ground, and an inner portion, more soft and friable, consisting of several cellular layers. The layer nearest the outer husk contains vegetable fibrin and fatty matter. The second layer is largely composed of gluten cells; while the center comprising the bulk of the grain, is chiefly made up of starch granules with a small proportion of gluten.
Sectional View of Wheat Kernel.
The structure of a wheat kernel is well illustrated in the accompanying cut. As will be seen, the different food elements are situated in different parts of the grain, and not uniformly distributed throughout its structure. The outer husk of the berry is composed wholly of innutritious and indigestible matter, but the thin layers which lie next this outer covering contain the larger proportion of the nitrogenous elements to be found in the entire kernel. The central portion consists almost wholly of farinaceous matter.
Phosphates and other mineral matter are present to some extent throughout the entire grain, but preponderates in the external part. Here is also found a peculiar, soluble, active principle called diastase, which possesses the power of converting starch into sugar. The dark color and marked flavor of Graham bread is undoubtedly due to the influence of this element.
Until within a few years the unground grain was rarely used as an article of food, but people are beginning to appreciate its wholesomeness, and cracked, rolled, and pearled wheats are coming rapidly into favor. Cracked wheat is the grain cleaned and then cut into two or more pieces; in rolled wheat the grains are mashed between rollers, by which process they are thoroughly softened in every part, and are then easily cooked. Pearl wheat is the whole grain cleaned and dressed. The whole grain is also cooked sometimes in its natural state.
Preparation and cooking.—Few articles of food show greater difference between good and poor cooking than the various grains. Dry, harsh, or underdone, they are as unwholesome as unpalatable. Like most of the grains, wheat, with the exception of new wheat boiled whole, should be put into boiling water and allowed to cook continuously but slowly until done. Any of the unground preparations require prolonged cooking. The average length of time and the approximate amount of water needed in cooking one cupful of the various wheat preparations in a double boiler is stated on [page 82].