Chow Line: Summertime Corn: How sweet it is (for 7/1/07)

June 22, 2007

What makes corn on the cob so sweet?

Ooh -- that's too easy. Sweet corn is sweet because of (drum roll, please) ... sugar!

Specific types of corn are grown just for the fresh sweet-corn market, and that, of course, makes a big difference on sweetness. But how ears are harvested and handled matters, too.

First, let's look at genetics: All corn has sugars, starch and polysaccharides -- different types of carbohydrates that give corn different qualities. Standard corn, used as animal feed or in the food industry, has a lot more starch, making it dryer and less sweet. Regular sweet corn has more sugars than field corn, as well as a lot more polysaccharides, which are complex sugars that are water-soluble and offer the advantage of making corn kernels creamy. "Super sweet" varieties of corn don't have nearly as many polysaccharides as regular sweet corn, but they do have a lot more sugars.

Harvesting and handling also makes a difference. Sweet corn is harvested just about three weeks after the corn is pollinated. The kernels are still immature -- sweeter and juicier than if they are left on the stalk longer. But sugars in sweet corn start converting to starch as soon as the cob is harvested. Gardeners who grow sweet corn in their back yard often wait to pick ears from the stalk until suppertime, when they quickly husk the corn and cook it immediately, hoping to catch as much sweetness as possible. This normally rapid conversion from sugar to starch is much slower in super sweet corn compared to regular sweet corn. You see super sweet corn in the corn in supermarkets in early summer -- it comes from southern states, but experts say it tastes almost like local sweet corn. Local sweet corn, from Ohio's southern counties, becomes available near the end of June.

When buying corn at the grocery store or farmers' market, choose the freshest possible -- look for moist husks and ears. And watch out for indentations in the kernels -- they signal the corn is old (too long of a period since harvest) or is overripe. If you're not planning to cook the corn that day, you can save some of the sweetness by storing the cobs in ice water.

Corn is a good source of fiber, folate, thiamin and phosphorus, and it's not a bad source of vitamin C. Yellow corn also offers vitamin A in the form of beta carotene -- including zeaxanthin, which is especially good for eyesight. A medium-sized ear (about 7 inches long) has 110 calories.

When you enjoy the corn, be sure to go light on the salt and butter. A eighth of a teaspoon of salt adds 290 milligrams of sodium. A tablespoon of butter adds 100 calories. Try skipping the salt completely --you might find you enjoy the flavor of fresh corn without it. And instead of solid butter or margarine, try a pump spray -- it's a less-messy, less-calorie alternative.

Chow Line is a service of Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH, 43210-1044, or filipic.3@cfaes.osu.edu.

Editor: This column was reviewed by Hugo Melgar-Quinonez, assistant professor of human nutrition in the College of Education and Human Ecology, and Bob Precheur, associate professor of horticulture and crop science in the College of Food, Agricultural, and Environmental Sciences. Both have appointments with Ohio State University Extension and the Ohio Agricultural Research and Development Center.

Author(s): 
Martha Filipic
Source(s): 
Hugo Melgar-Quinonez, Bob Precheur