Milling and Refining

People began treating the grains to remove their tough protective layers in prehistoric times. Milling breaks the grains into pieces, and refining sifts away the bran and germ. The very different mechanical properties of endosperm, germ, and bran make this separation possible: the first is easily fragmented, and the others are oily and leathery respectively. The germ and the bran—which in practice include the aleurone layer just underneath it—together account for most of the fiber, oil, and B vitamins contained in the whole grain, as well as some 25% of its protein. Yet these parts of the grain are usually removed entirely or in part from rice and barley grains, and from cornmeal and wheat flours. Why this waste? Refined grains are easier to cook and to chew, and more attractively light in color. And in the case of flours, the high lipid concentrations in the germ and aleurone layer shorten the shelf life of whole-grain flours substantially. The oils are susceptible to oxidation and develop rancid flavors (stale aroma, harsh taste) in a matter of weeks. Today most refined cereals in industrial countries are fortified with B vitamins and iron in order to compensate for the nutrients lost with the bran.