Bran, Germ, and Endosperm

The wheat kernel is enclosed by several outer husk layers known collectively as the pericarp (fruit coat). These layers serve as the protective coating of the germ and endosperm. The edible bran layer of the kernel resides just inside the pericarp. The innermost of these bran layers is known as the aleurone. Although it is technically the outer surface of the endosperm, the very nutrient rich aleurone is removed along with both the pericarp and the bran layer prior to the milling of white flour (except when flour is stone ground as opposed to roller milled; milling with stones results in both the aleurone and the germ becoming integrated in the endosperm). The bran layers constitute about 14 percent of the wheat kernel, and are comprised primarily of cellulose and minerals.