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Long-Cooked Corn Higher in Antioxidant

A taste of summer
Child enjoys roasted 'Olathe Sweet' sweet corn at 1999 Festival." Photo for "Olathe Sweet Corn Festival in Colorado," a Colorado Local Legacies project

August 10, 2002. -- Cooking sweet corn at high temperature for a long time unleashes beneficial nutrients that can substantially reduce the chance of heart disease and cancer, according to Cornell University food scientists.

Cooking sweet corn for close to an hour, these researchers at Cornell in Ithaca, NY, say in the August 14 issue of Journal of Agriculture and Food Chemistry, 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.

Lui and his student cooked batches of sweet corn kernels at 115 degrees Celsius/239 degrees Fahrenheit (a rolling boil). The kernels produced more antioxidants the longer they cooked. After 10, 25 and 50 minutes the antioxidant content was boosted by 22, 44 and 53 percent, respectively.

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."

In the corn cooked at 115 degrees Celsius (239 F) for 10, 25 and 50 minutes, ferulic acid 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."

Other plant foods that contain high levels of ferulic acid include rice bran, which may to lower blood pressure and blueberries and blackberries.

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.

/Rui Hai Liu with a student in the Department of Food SciencesRui Hai Lui, lead author on the article, "Processed Sweet Corn Has Higher Antioxidant Activity," had research help from Veronica Dewanto, a Cornell graduate student from Indonesia, and Xianzhong Wu, a visiting scholar from China. Professor Liu's research program focuses on diet and cancer, functional foods and nutraceuticals. Specific interests include:

1) role of conjugated linoleic acid (CLA) in the prevention of cancer;
2) antioxidant and anticancer activities of phytochemicals in fruits and vegetables;
3) functional foods for disease prevention and health promotion: roles of antioxidants, phytochemicals and other bio-active compounds targeted at aging, cancers, cardiovascular and inflammatory diseases;
4) screening of natural products and herbal formulations for antiviral activity to hepatitis B and C.

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