“It’s conventional wisdom that processed fruits and vegetables have lower nutritional value than sweet fresh produce,” said Rui Hai Liu, M.D., Ph.D., assistant professor of food science at Cornell University. But Liu’s ongoing investigation of fruits and vegetables contradicts conventional wisdom.

In one study, published two years ago in Nature, Liu and his team found that less than 0.4 percent of an apple’s antioxidant activity comes from vitamin C. Instead, a combination of phytochemicals supplies the antioxidants in apples. This led Liu to suspect that processed fruits and vegetables might actually maintain their antioxidant activity despite the loss of vitamin C.

Earlier this year, in another study published in the Journal of Agricultural and Food Chemistry, the researchers reported more evidence that processing is beneficial. They found that cooking tomatoes triggers a rise in total antioxidant activity, chiefly due to an increase in lycopene–a phytochemical that makes tomatoes red. The findings are obviously good for the processing industry, Liu said, but they are also good for the consumer.