Bran -Takes up about 14% of the kernel weight. The bran is included in whole wheat flour and is also available separately. The bran contains a small amount of protein, large quantities of the three major B vitamins, trace minerals and dietary fiber -- primarily insoluble.
Endosperm -Takes up about 83% of the kernel weight and the source of white flour. The endosperm contains the greatest share of protein, carbohydrates and iron, as well as the major B-vitamins such as riboflavin, niacin, thiamin and iron. It is also a source of soluble fiber.
Germ - Takes up about 2.5% of the kernel weight. The germ is the embryo or sprouting section of the seed, often separated from flour in milling because the fat content (10 percent) limits shelf life. The germ contains minimal quantities of high quality protein and a greater share of B-complex vitamins and trace minerals. Wheat germ can be purchased separately and is included in whole wheat flour.