Getting best health benefit from corn

Harry Surjadi, Contributor, Jakarta

Many people's lives have been touched in some way by cancer. Maybe you have lost a relative, a friend or an acquaintance. Maybe you have had a scare as a result of an annual physical examination.

According to Cornell University food scientists, cooking sweet corn, whether you cream it, steam it or keep it on the cob, unleashes beneficial nutrients that can substantially reduce the chance of heart disease and cancer.

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.

"The inverse association between consumption of fruits and vegetables and the risk of developing chronic diseases for example, cancer has been well-established. But 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," said Liu Ruihai, Cornell assistant professor of food science, and Veronica Dewanto, the lead author of the article and Xianzhong Wu, a visiting scholar from China helped in the analysis.

"Processed sweet corn has higher antioxidant activity," said Veronica, who just finished her study and came back to Indonesia several months ago. She is now working for a private company in Pasuruan, East Java.

The researchers purchased sweet corn and cooked the kernels in batches at 115 degrees Celsius for 10, 25, and 50 minutes. The cooking increased the antioxidant in sweet corn by 22, 44, and 53 percent respectively.

In addition to its antioxidant benefits, cooked sweet corn unleashes a phenolic compound called ferulic acid, which has added health benefits, such as it battles cancer. Ferulic acid (C10H10O4) is a compound related to vanillin and is obtained from certain plants.

"It's not a free acid," said Veronica Dewanto. "It's bound to cell walls 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, Veronica with the guidance from her advisor Liu Ruihai, cooked sweet corn at 115 degrees Celsius for 10, 25, 50 minutes. Ferulic acid amounts increased by 240 percent, 550 percent and 900 percent respectively.

"Ferulic acid, a phytochemical, is unique. It is found in very low levels in fruits and vegetables but is found in very high levels in corn," said Liu as quoted in the recent press release issued by American Chemical Society (www.acs.org/portal/Chemistry/).

Phenolic compound in sweet corn and other grains exist in three different forms -- the free phenolic acid form, the soluble-bound and the insoluble bound phenolic acid forms. Ferulic acid is the predominant bound phenolic acids in sweet corn constituting about 78 percent of the total phenolic acid, explained Veronica Dewanto.

"When you cook the sweet corn, you release ferulic acid, and what you are losing in vitamin C, you are gaining in ferulic acid and total antioxidant activity," she added.

Dewanto said the reason why they worked on sweet corn is because of their prior work on the effect of heat processing on tomatoes. On tomatoes, they didn't observe any significant increase or decrease in the phenolics content although they observed an increase in bioaccessible lycopene.

"We think that tomatoes are not high in phenolic acid which might explain for the insignificant observation thus we decided to work on another 'vegetable' that is high in phenolics, therefore we picked to work with sweet corn," said Dewanto who started the research from August 2001 until March 2002.

Furthermore, sweet corn and tomatoes are highly processed like canned tomato soup, tomato juice and canned sweet corn. Tomatoes and sweet corn are the most processed vegetable and fruit in the US.

The researchers would like to know whether heat processing affects these health benefits as well. In addition, they were also inspired by the lab's finding that vitamin C only contributed less than 0.5 percent of the total antioxidant activity in apples (published in Nature, 2000).

"This leads us to the hypothesis that most of the antioxidant activity comes from other phytochemicals such as phenolic acids, flavonoids and carotenoids. It has been known that vitamin C is degraded by thermal processing; therefore we would like to know if the nutritional value of processed vegetables is affected negatively by heat processing," said Veronica.

According to Veronica sweet corn planted in Indonesia also contains the same ferulic acid. Actually, most grains -- including rice, corn and oats -- contain phenolic acids with the antioxidant activity. "But the effect of heat treatment should vary on the phenolic acids and antioxidant activity from vegetables to vegetables," explained Veronica.

Ferulic acid is relatively heat stable but if cooked too long, it will also oxidize and degrade like vitamin C. So, therefore, needs an optimal cooking time.

In addition, severe heat treatment may also effect the taste and the texture of the corn. "We worked with the sweet corn by simulating the processing condition that is followed commercially. Within the increasing cooking temperature and time parameters, we observed increased free ferulic acid content. However, if we increased the temperature and time further, we expected the phenolic acids to decline.

"I would recommend that we obtain our phytochemicals to reduce the risks of developing chronic diseases by eating a variety of fruits and vegetables and not solely corn. This is because fruits, grains and vegetables have unique phytochemical profiles. In the US, people are recommended to eat five servings of fruits and vegetables per day."