Most of us are familiar with sweet corn, which is the corn we see on our dinner tables. We also know about popcorn, a favorite movie snack. Many of us, however, aren't aware of field, or grain corn. The truth is that of the approximately 68 million acres of corn planted in the United States annually, almost 88 percent is allocated to field corn. Sweet corn accounts for almost 12 percent of the acreage, and about three tenths of 1 percent is devoted to popcorn.
Grain, or Field Corn
Field corn is divided into four major types--dent corn, flint corn, flour corn and waxy corn. Both dent and flint corns are used primarily for animal feed, with a small amount being reserved for human consumption, as corn meal, grits and polenta. Fully ripe dent corn has a hollow, or dent, at the top of its kernels. Each kernel has a hard form of starch at the sides, with a center of soft starch. As the kernel ripens, the soft starch shrinks. This causes the dent at the end of the kernel. Dent corn kernels vary in shape; some are long and narrow and others are wide and shallow. Dent corn makes up most of the field corn grown in the United States. With flint corn, hard starch completely surrounds the outer part of the kernel, so the kernel does not sink in and develop a dent at the top. Flour corn is used as the name implies, for cornflour or corn starch. Flour, or soft corn kernels, are almost completely soft starch, with a thin layer of hard starch. Not much flour corn is grown commercially. Waxy corn gets its name from the waxy appearance of the endosperm when it is broken or cut. Waxy corn is used for industrial processes and not much of it is grown.
Sweet corn is divided into three types--normal sugary (SU), sugary enhanced (SE) and supersweet (Sh2). Nonhybrid sweet corn varieties have a sugary (SU) gene that creates the sweetness and creaminess associated with sweet corn. The SU qualities degrade very quickly, so SE varieties were developed. SE corn has a much higher sugar content but retains the creamy texture and tenderness of traditional sweet corn. Sh2 hybrids have a higher sugar content than either SU or SE varieties. The kernels have a very crisp, tough-skinned texture and lack the creaminess and traditional "corniness" of SU and SE corn. Although the lack of creamy texture is not especially noticeable in fresh corn on the cob, it affects the quality of frozen and canned corn, as does the toughness of the seed coat. Sh2 is also more difficult to grow and doesn't can or freeze as satisfactorily as SU or SE corn. SE corn is the most widely grown for eating today.
A popular snack for many people, popcorn has probably been eaten by natives in the western hemisphere for more than a thousand years. There are two types of popcorn--yellow and white. Yellow, or pearl popcorn, is more rounded in shape and varies in color from yellow to orange. It has a hull when it is popped. White, or rice popcorn, has white kernels, and is longer and pointed in shape. It is frequently called hulless popcorn, but it does have some hulls when popped.