Info

Note: Typical or average figure. NFE = nitrogen free extract (an approximate measure of the starch content). Source: Ref. 32.

Note: Typical or average figure. NFE = nitrogen free extract (an approximate measure of the starch content). Source: Ref. 32.

is sprouted) and vitamin D. Yellow corn differs from white corn and the other cereal grains in containing carotenoid pigments (principally cryptoxanthin, with smaller quantities of carotenes). These are convertible by the body to vitamin A. Wheat also contains yellow pigments, but they are almost entirely xanthophylls, which are not precursors of vitamin A. The oils of the embryos of cereal grains are rich sources of vitamin E. The relative distribution of vitamins in the kernel is not uniform, although the endosperm invariably contains the lowest concentration.

The protein contents of wheat and barley are important quality indices for the manufacture of various foods. For example, the quantity and quality of wheat protein is critical in bread making. Cereal grains contain water-soluble proteins (albumins), salt-soluble proteins (globulins), aqueous alcohol-soluble proteins (prolamins), and acid-and alkali-soluble proteins (glutelins). The prolamins are characteristic of the grass family, and together with the glutelins, comprise the bulk of the proteins of cereal grains. The following are names given to prolamins in proteins of the cereal grains: gliadins in wheat, hordeins in barley, zeins in maize, avenins in oats, kaffirins in grain sorghum, and secalins in rye.

The various proteins are not distributed uniformly in the kernel. Thus, the proteins isolated from the inner endosperm of wheat consist chiefly of prolamins (gliadin) and glutelins (glutenin). The embryo proteins consist of nucleo-protein, an albumin (leucosin), and globulins, whereas in wheat bran a prolamin predominates with smaller quantities of albumins and globulins. In the presence of water, the wheat endosperm proteins, gliadin, and glutenin form a tenacious colloidal complex known as gluten. Gluten is mostly responsible for the superiority of wheat over the other cereals in the manufacture of leavened products because it makes possible the formation of a dough that retains the carbon dioxide produced by yeast or chemical leavening agents. The gluten proteins collectively contain 17.55% nitrogen. Consequently in estimating the crude protein content of wheat and wheat products from the determination of total nitrogen, the factor 5.7 is normally employed rather than the customary value of 6.25. The latter value is based on the assumption that proteins contain an average of 16% nitrogen.

In general, cereal proteins are not as high in biological value as are those of certain legumes, nuts, or animal products. Most cereals are low in lysine and tryptophan. Oats are a notable exception to this generalization. The biological value of whole cereal grains is greater than that of refined milled products, which consist chiefly of the endosperm. Studies have shown that adults, if satisfying their calorie needs, will not be protein deficient on nearly 100% cereal diets. This may not be true for young children or pregnant women. In general, American and Western European diets normally include animal products as well as cereals and, thus, satisfy protein requirements many times over. Under these conditions, the different proteins tend to supplement each other.

The predominant form of carbohydrate in cereals is starch, which is the primary source of calories provided by the grains. Most of the carbohydrates are in the starchy endosperm.

Table 5. FDA Cereal Enrichment Standards

Product

Thiamine (mg/lb)

Riboflavin (mg/lb)

Niacin (mg/lb)

Iron (mg/lb)

Calcium (mg/lb)

Vitamin D (lU/lb)

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