(Sept. 4) ITHACA, N.Y. — A recent Cornell University study on sweet corn seems to be putting a lid on age-old beliefs that fresh fruits and vegetables are more nutritious than canned produce.

However, the lead author of the study, “Processed Sweet Corn Has Higher Antioxidant Activity,” published Aug. 14 in the American Chemical Society’s Journal of Agriculture and Food Chemistry, emphasizes that consumers should not infer that fresh produce is less nutritious than its canned counterpart.

The researchers, nevertheless, reported that the heat processing of sweet corn actually raises the level of naturally occurring compounds that help fight diseases over those of raw, uncooked product.

Specifically, the heating of corn before it is canned increases the total antioxidant activity of the corn by approximately 44%, said Rui Hai Liu, a professor of food science who headed the study at Cornell.

Cooking fresh corn, under similar circumstances, and by controlling water loss, results in similar increases in phtyochemical activity, he added.

“If you cook it, it will release the phytochemical,” he said. “It doesn’t mater if you cook it, you boil it or steam it.”

“It’s conventional wisdom that processed fruits and vegetables have lower nutritional value than sweet fresh product,” Liu said. “But we found that heating sweet corn, whether on the cob, in a casserole or in the can, enhances its beneficial compounds.”

If anything, he said, the results of the study indicate that fruits and vegetables of all kinds are far preferable to artificial supplements.

“I’m not telling people that (processed) is better than fresh; it doesn’t matter if it’s raw, cooked, processed or fresh,” Liu said. Liu and his research team have conducted similar studies on the nutritional value of apples and canned tomatoes. Early in 2002, for example, Liu and his team reported that cooking tomatoes leads to a rise in the product’s total antioxidant activity, primarily because it increases levels of lycopene, the chemical that makes tomatoes red.

“Antioxidants are very important,” he said. “For consumers, if you want to improve your heath, you need the antioxidants from the fruits and vegetables, not from dietary supplements. That’s the main message here.”

According to conventional wisdom, heat reduces the vitamin content of fruits and vegetables. However, Liu and his team found that it also unlocks other nutrients, at least in the commodities they have studied.

“I think, maybe, processing breaks down the cell matrix (in the product) that releases some of the phytochemicals that are bound to the cell matrix,” Liu said.

Processing leads to a decrease in levels of vitamin C, the antioxidant that helps prevent cell and tissue damage and is thought to give produce its disease-fighting potency.

But Liu’s research has shed light on the connection between vitamin C in produce and good health.

In a study of apples published in 2000, Liu and his team found that less than 0.4% of an apple’s antioxidant activity comes from vitamin C. They found, instead, that a combination of the phytochemicals supplies the antioxidant potency of apples.