BOSTON—Almost everyone loves a good tomato, so why are they so hard to find? Two researchers here at the annual meeting of AAAS (which publishes ScienceNOW) explained the nature of the problem and what they're doing to create a supermarket tomato that more people would want to eat. Here are some of the top questions that came up during the packed session.
Q: Argh, why are supermarket tomatoes are so darn tasteless?
A: This is biology, compounded by economics. Consumers want tomatoes year-round, and most people don't want to pay a lot of money for their food. Starting after World War II, plant breeders focused on boosting yield to lower prices and improving durability to facilitate long-distance shipping during the winter. Modern commercial tomatoes are bred to produce a lot of fruit very quickly, because most of the cost is in the labor of picking them. "Breeders have added more fruits and filled them up with water," said Harry Klee, a tomato breeder at the University of Florida (UF), Gainesville. The plants can't put as many nutrients and volatiles—chemicals that easily evaporate—into the fruit as they used to. And that means less flavor.
Q: Why are volatiles so important?
A: A delicious tomato has a balance of acids and sugars that play on the tongue. But it also has volatiles that waft into the nose. Klee and Linda Bartoshuk, a psychologist at UF who studies sensory perception, have found that among the 100 or so volatile compounds in tomatoes, six enhance the sweetness of the tomato. "We didn't know that this happened in tomatoes," Bartoshuk told the audience. For example, varieties called matina and yellow jelly belly have exactly the same amount of sugar, yet matina tastes twice as sweet because of the volatiles.
Q: Is that why shouldn't you refrigerate tomatoes?
A: Yes. That might seem counterintuitive, because volatiles easily evaporate—so cold ought to lessen that effect, right? Not so, said Klee. Tomato fruits are constantly making more volatiles to replace those that have evaporated. Low temperatures stop the synthesis of new volatiles, so all those flavor compounds vanish. “Never, ever, ever, ever refrigerate your tomatoes,” Klee said.
Q: How do you create a more flavorful, but economically viable tomato?
A: Start with heirloom varieties. These have more flavor, but the plants yield less fruit and have a shorter shelf life, both of which make them more expensive. (In addition, the exotic shapes and colors don't have as wide an appeal as perfectly round and red tomatoes.) Klee and his colleagues have studied the chemicals inside heirlooms, figured out which ones most people tend to like, and started to identify the genes that control the synthesis of volatiles. They are working to add these genes to high-yielding, disease-resistant varieties that farmers want.
Q: Will these new tomatoes be genetically modified (GM)?
A: No. Getting GM tomatoes through the regulatory approval process can cost $15 million and is too expensive for academics, Klee said. Genomics are helping to speed up the breeding process. The sequence of the tomato genome was published last year, and Klee's colleagues are also sequencing heirlooms.
Q: When will tastier tomatoes be available?
A: Klee's team has produced hybrids of heirlooms and commercial varieties that might be appropriate for smaller farms that supply niche markets. "I think the farmers will love this stuff," he said. They taste good and have double the yield of heirlooms. But that's still not suitable for the large growers. "It's going to take a long time to make an industrial strength tomato taste like an heirloom."
Q: So what should I buy in the mean time?
A: Farmers markets have good tomatoes in season. As for the rest of the year, Klee says the only supermarket tomato he will buy is a variety called campari that is sold on the vine. Otherwise, your best bet are cherry tomatoes, which tend have more sugar than larger tomatoes. Some supermarkets carry a new variety called Tasti-Lee. This tomato, breed by other researchers at the University of Florida, has better flavor and more lycopene that most commercial varieties.
Q: OK, I'm not a foodie. Why does this matter?
A: Klee believes that bland supermarket offerings mean that people avoid eating tomatoes, which are a good source of lycopene and other nutrients. Although the bland varieties still have these nutrients, that doesn't do any good if people don't eat them. Improving the flavor would help improve nutrition. Even non-foodies would approve.