Writing in the Aug. 14 issue of Journal of Agriculture and Food Chemistry , published by the American Chemical Society, the Cornell researchers say that cooking sweet corn significantly boosts the grain's health-giving antioxidant activity.
"There is a notion that processed fruits and vegetables have a lower nutritional value than fresh produce. Those original notions seem to be false, as cooked sweet corn retains its antioxidant activity, despite the loss of vitamin C," says Rui Hai Liu, Cornell assistant professor of food science, the lead author on the article, "Processed Sweet Corn Has Higher Antioxidant Activity." Veronica Dewanto, a Cornell graduate student from Indonesia, and Xianzhong Wu, a visiting scholar from China, joined Liu in the research.
The researchers purchased sweet corn and cooked the kernels in batches at 115 degrees Celsius (239 degrees Fahrenheit) for 10, 25 and 50 minutes. Liu says that the cooking increased the antioxidants in sweet corn by 22, 44 and 53 percent, respectively. The scientists measured the antioxidants' ability to quench free radicals, which cause damage to the body from oxidation, increasing the risk of cancer and heart disease. Free radicals also have been linked to aging-related diseases like cataracts and Alzheimer's.
In addition to its antioxidant benefits, cooked sweet corn unleashes a phenolic compound called ferulic acid, which provides health benefits, such as battling cancer. "It's not a free acid," says Liu. "It's bound to the cell wall and in the corn's insoluble fibers. We found that ferulic acid was substantially increased after the sweet corn was cooked at high temperatures and by cooking it at the same temperature over a longer time."
To find the ferulic acid, a long-known antioxidant in grains, Liu and his colleagues cooked sweet corn at 115 degrees Celsius (239 F) for 10, 25 and 50 minutes. Ferulic acid amounts increased by 240 percent, 550 percent and 900 percent, respectively."Ferulic acid, a phytochemical, is unique in that it is found in very low amounts in fruits and vegetables, but is found in very high levels in corn. You find it mostly in grains," says Liu. "Ferulic acid, which is good for you, is found mainly in its bound form. Cook the sweet corn and the amount of ferulic acid increases a lot. When you cook it, you release it, and what you are losing in vitamin C, you are gaining in ferulic acid and total antioxidant activity."
Liu, who previously studied apples and tomatoes, says corn is quite a different model. "The tomato is rich in lycopene but has very low amounts of phenolic compounds. Sweet corn is very high in phenolics," he says.