If you're trying to eat healthy, you might be better off reaching for a can of corn instead of a fresh ear. Cooking sweet corn increases its disease-fighting antioxidant activity, despite decreasing its vitamin C content, a new study reports. Canned corn, tortillas, and some baked goods are among many foods that contain heat-processed corn.
"People think that cooked fruits or vegetables are low in nutritional value. That's not true," says Rui Hai Liu of Cornell University, a coauthor of the study, which appears in the Aug. 14 Journal of Agricultural and Food Chemistry.
Liu and his colleagues stripped kernels from fresh ears of sweet corn, put them in containers, and heated them to 115C for 10, 25, or 50 minutes and to boiling (100C) or 121C for 25 minutes. Canned corn is typically heated to 115C for 25 minutes. The scientists found that both the hotter the temperature and the longer the heating times, the more the corn neutralized free radicals–molecules that promote heart disease and cancer. Correspondingly, concentrations of the potent antioxidants called phenolic acids increased with time and temperature of heating.
Cooking appears to release chemicals that are otherwise bound to the plant fibers and unavailable for a person's gut to absorb, Liu says. Scientists have already reported that cooking tomatoes increases their concentration of lycopene, another antioxidant.
"I'm not encouraging people to just cook all the vegetables in the fridge," Liu concludes, "but I am saying you need a variety of fruits and vegetables, raw and cooked."
Rui Hai Liu
Department of Food Science
Ithaca, NY 14853
Dewanto, V. . . . and R.H. Liu. 2002. Thermal processing enhances the nutritional value of tomatoes by increasing total antioxidant activity. Journal of Agricultural and Food Chemistry 50(Aug. 14):3010-3014.
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