To process wheat, farmers harvest the crop, cut the heads off the tops of the plants, thresh the wheat plants to separate the grains from the chaff, separate the grains from other plant fragments, and clean the grains. Workers transport the grain to a mill for separation of the bran, endosperm and germ, if desired.
Mill operators pass the wheat through automated steel cylinders or crush the wheat with grinding stones to separate the bran, endosperm and germ. Typically the mill operator adds a little water to the grains. Water makes the inner endosperm softer and simultaneously hardens the outer bran so that the two parts are easier to separate. Usually, mill workers use a roller to flatten the wheat germ before sifting out the remaining flour. The phase at which the mill operators remove the wheat germ determines the type of flour produced.
Whole wheat goods contain the endosperm, the bran and the wheat germ. Because all three components remain, whole wheat products offer consumers the largest variety of nutrients. To make white bread and bleached white flour, mill operators remove the bran and the endosperm. Because the wheat germ contains fat, it can become rancid in flour if not properly stored. Manufacturers sometimes use wheat bran independently as an ingredient in breakfast cereals, bran muffins and animal food.