Clues to Redder, More Nutritious Tomatoes

Tomatoes with much more lycopene than those now found in stores may be on the horizon if ARS research pans out.

Epidemiological research has shown that lycopene, which gives tomatoes their bright-red color, may help reduce the risk of some cancers.

While working with tomato tissue cultures, ARS biologist Betty K. Ishida serendipitously uncovered clues about ripening and lycopene formation. As expected, the culture developed into a cherry tomato. Surprisingly, the fruit's green outer leaves, known as the calyx, also ripened into fruitlike tissue.

"We discovered that in this particular tomato, called VFNT cherry, low growing temperatures trigger ripening in nonfruit tissue," says Ishida. Because the fruit was very dark red, they also tested the lycopene content. It was 10 times the amount found in most commercial tomatoes.

But the process doesn't work outside tissue culture. "Something else in the plant prevents this transformation into fruit," she says.

Ishida is on the trail to find the trigger that turns on the gene responsible for the increased lycopene. "When we find that, we can apply it to commercial varieties," she says.

Medical researchers have shown that the lycopene in processed tomato products—like spaghetti sauce—is absorbed to a greater extent than lycopene in the fresh fruit.

Ishida is looking at how different forms of lycopene develop. And she wants to find out if changing the form would increase the nutritional benefits of her high-lycopene tomatoes.

"In tomatoes, lycopene is a long-chain molecule," Ishida says. "But in human blood plasma, lycopene appears in several different shapes—the chain is 'bent' in various ways." Tomatoes with the bent form (known as "cis"-lycopene) might be more beneficial if this lycopene were more easily absorbed. She plans to develop tomatoes with high cis-lycopene for testing.

"The goal of this research is to produce tomatoes that have more value to consumers," she says.—By Kathryn Barry Stelljes, Agricultural Research Service Information Staff.

Betty K. Ishida is in the USDA-ARS Process Chemistry and Engineering Research Unit, Western Regional Research Center, 800 Buchanan St., Albany, CA 94710; phone (510) 559-5726, fax (510) 559-8777.

"Clues to Redder, More Nutritious Tomatoes" was published in the October 1999 issue of Agricultural Research magazine.