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Grains form the base of the Food Guide Pyramid, and nutritionists are constantly nagging us to eat more of them, since they're high in nutrients, low in fat, and dirt cheap.
Cooks usually consign grains to supporting roles, letting them absorb the flavors of other ingredients while adding texture and body. It often helps to toast grains briefly before cooking them so as to bring out the flavor and speed up the cooking time.
Most grains have been processed by the time they reach us. The first step at the mill is to remove the inedible outer hull, yielding what's called a whole grain, berry, or groat. Whole grains are nutritious, but they're chewy and slow to cook.
To fix that, the nutritious bran layer beneath the hull is sometimes scoured off as well, resulting in a pearled or polished grain. Whole or polished grains are then sometimes ground, rolled, or chopped into flakes, small grits, meal, or flour.