Third—The fats, occurring chiefly in the germ of the grain.
Fourth—The phosphorous compounds, iron and lime, found in the bran.
The kernel of wheat consists of the bran or covering, which surrounds the white, pulpy mass of starch within. In the lower end of the kernel is the germ.
Flour. In the old time process of making flour the wheat was crushed between stones and then sifted, first, through a sieve, which separated the outer shell of the bran; then through bolting cloth, which separated the white pulp from the inner bran coating. It was not ground as fine as in the present process, thus the gluten, phosphorous, and iron (valuable foods) were, in the old process, nearly all left out of the white flour. The second bran coating, left by the second sifting, was not so coarse as the outer shell but coarser than the inner. Care was not formerly observed in having the grain clean before grinding, the bran containing chaff and dirt, so that it was not used as food but was considered valuable for stock and was called “middlings.”
The modern process of crushing the wheat between steel rollers, crushes it so fine that the white flour of to-day contains more of the protein from the inner coat of the bran than the white flour of the old process; hence, it is more nutritious.
Bran. Objection is sometimes made to bran because the cellulose shell is not digested, but bran contains much protein and mineral matter and, even though it is crude fiber, as stated above, this fiber has a value as a cleanser for the lining of stomach and intestines, and for increasing peristalsis, thus encouraging the flow of digestive juices and the elimination of waste. In bread or breakfast foods, it is desirable to retain it for its laxative effect.
The bran has three coats,—the tough, glossy outside, within this a coat containing most of the coloring matter, and a third coat, containing a special kind of protein, known as cerealin. The two outer layers contain phosphorous compounds, lime, and iron. All three coats contain gluten.
Of course there is more waste in bread made with bran and in consequence, there is a smaller proportion of the nutrition in graham bread. It is held by some, however, that more of the nutrition is digested than in white bread.
Gluten flour is made of the gluten of wheat. It is a valuable, easily digested food, containing a large proportion of protein.
Whole wheat flour does not contain the whole of the wheat, as the name implies; it, however, does contain all the proteins of the endosperm and the gluten and oil of the germ, together with all of the starch. As a flour, therefore, it is more valuable than the white flour, containing more nitrogenous elements.