Taking Tomatoes Back To Their Tasty Roots
Scientists in Florida have a noble aspiration: They want to restore the supermarket tomato to something that tastes more like a tomato than a piece of cardboard. The researchers say it will take a combination of psychology and genetics to accomplish their goal.
Breeding a tomato that consumers will like because it tastes good isn't that hard. And breeding a tomato that farmers will like because it has a high yield is also fairly straightforward. Getting both qualities in one plant is the tricky part.
The Business Of Tomatoes
U.S. farm sales of tomatoes rake in more than $2 billion every year. By value, the most-sold tomato varieties in 2008 were hothouse tomatoes on the vine, grape tomatoes, and round field tomatoes, in that order. Heirloom tomatoes, or nonhybrid tomatoes, accounted for 1 percent of tomatoes sold in the U.S. in 2008.
While many U.S. stores sell genetically modified products, particularly corn and soy, tomatoes in U.S. supermarkets have not been genetically engineered. Most store-bought tomatoes are hybrids, which have been naturally bred for a longer shelf life and ease of transport.
Genetically engineered foods are made by introducing DNA into a plant that wasn't there before. But naturally bred products are made by mating two plants that are reproductively compatible — much like the breeding of dogs.
Many tomatoes bred for shipping long distances have a mutated gene that slows down their ripening process. Unripe tomatoes travel better, but once they arrive at the warehouses near their destination, they need help to ripen.
This is where ethylene gas comes in. Ethylene is a natural hormone that plants create; in tomatoes, it signals them to ripen. After tomatoes are shipped, but before they are delivered to the grocer, stacks of boxes of tomatoes go into a huge room that is pumped full of ethylene gas. After about a week, they're ready to head to the grocer.
— Rose Raymond
Sources: USDA, Produce Business, Harry Klee, professor, University of Florida, Encyclopaedia Britannica
The pressure for high-yield plants is responsible for the dismal taste of the supermarket tomato. Harry Klee, a plant biologist at the University of Florida in Gainesville, says it's a simple matter of economics.
"The grower is paid for size and yield -- and flavor is irrelevant, unfortunately," Klee says.
In fact, the yield is so great for some tomato varieties that the plant can't keep up. Because the plants have been bred to produce so many fruits, they can't produce enough sugars and other nutrients.
"And so what happens is you start to dilute out all of the good flavor compounds, and you get a fruit that you bite into it and it largely tastes like water," Klee says. "Because that's mostly what it is."
Satisfying Growers And Aficionados
But Klee thinks there's a way to improve the taste, without sacrificing yield. The secret is in a class of chemicals called volatiles. These are what give tomatoes much of their distinctive smell and taste.
"There's much more potential to increase the volatiles than there is the sugars or the acids," Klee says. "We think we can make huge improvements in the flavors without sacrificing all of the yield."
But determining which volatiles are crucial for a pleasing taste and smell is a job for psychologists. So Klee joined forces with Linda Bartoshuk. She's an expert in measuring relative tastiness. She discovered supertasters, people who taste everything far more intensely than the rest of us.
She says by developing the proper measurement tools, she can tease out what people most like about tomatoes. She'll then use that information to help Harry Klee zero in on the qualities he needs to build his tastier tomato.
To achieve Bartoshuk's recipe, Klee will take genes from existing tomato varieties. Many of the key genes are likely to be found in wild tomatoes. These plants produce tiny fruit -- only slightly larger than a pea -- but they have an intense tomato-y flavor.
The good news is, molecular genetics has speeded up plant breeding enormously. One lab can now do what it used to take thousand of breeders to do.
"And with modern molecular breeding tools," says Klee, "I can do that in months instead of years."
The tomato-loving world will be waiting anxiously.
RENEE MONTAGNE, host:
Some scientists in Florida have a noble aspiration: They want to restore the supermarket tomato to something that tastes more like a tomato than a mushy piece of cardboard. As NPR's Joe Palca reports, the researchers say it will take a mix of genetics and psychology to do that.
JOE PALCA: There are dabblers, and then there are the true tomato aficionados. University of Florida plant biologist Harry Klee falls into the latter category. And if you show a modicum of interest, he'll take you on a tour of his greenhouse. It looks a bit like an overgrown jungle of tomatoes.
Professor HARRY KLEE (Plant Biologist, University of Florida): So what we're looking at here basically is a genetic history of tomato, and it's all laid out for you right here in front of you.
PALCA: Kind of a tomato obstacle course. I'm going to smell like a tomato when I'm done here.
Prof. KLEE: Yes, you are, unfortunately.
PALCA: That's all right. I love that smell.
Prof. KLEE: This is where we really start with the wild accessions of tomato.
PALCA: An accession is just the term horticulturists use to describe each sample they collect from a field trip. The wild tomato is an itty-bitty thing, not much larger than a pea. But inside are the genes that Klee hopes will let him recapture a tomato's tomato-ness.
Prof. KLEE: People always say: Oh, those evil breeders. What did they do to my tomatoes? The reality is you just have to understand basic economics.
PALCA: Klee says it's simple.
Prof. KLEE: The grower is paid for size and yield, and flavor is irrelevant, unfortunately.
PALCA: In fact, the yield is so great for some tomato varieties that the plant can't keep up. It can't produce enough sugars and other nutrients.
Prof. KLEE: And so what happens is you start to dilute out all of the good flavor compounds, and you get a fruit that, you bite into it, and it largely tastes like water. Because that's mostly what it is.
PALCA: But Klee thinks there's a way to improve the taste, making tomato lovers happy, and keep the yield, making growers happy. The secret is in a class of chemicals that play on our senses, chemicals called volatiles. These are what give tomatoes much of their distinctive smell and taste.
Prof. KLEE: There's much more potential to increase the levels of the volatiles than there is the sugars and the acids. We think we can make huge improvements in the flavors without sacrificing all of the yield.
PALCA: But which volatiles, and what amount will bring people closer to tomato ecstasy? To find out, Klee has enlisted the help of the psychology department at the University of Florida to explore people's tastes.
Prof. KLEE: We are trying to bring some real science to the understanding of flavor, and that's the beauty of working with someone like Linda.
PALCA: Linda is psychologist Linda Bartoshuk. She's an expert in measuring relative tastiness. She discovered supertasters, people who taste everything far more intensely than the rest of us. She says by developing the right way to measure it, she can tease out what most people like about tomatoes. She'll use that information to help Harry Klee zero in on the qualities he needs to build his tastier tomato.
Professor LINDA BARTOSHUK (Psychologist, University of Florida): Is it possible that there exists a tomato better than any you have ever tasted, if only we could put the right combination together?
PALCA: It's all a question of putting the right genes together. Some of the genes Klee will need are likely to be in the wild tomatoes he's growing. He stops in front of plant near the glass wall of his greenhouse.
Prof. KLEE: So this is a wild relative of tomato here. You can see this is actually what the fruits look like. And these are full-sized and almost ripe.
PALCA: Klee pushes aside some leaves, plucks a small, red fruit, and hands it to me.
Prof. KLEE: Here's one you might want to taste.
PALCA: I pop it in my mouth, and it's instantly clear why.
Prof. KLEE: This is not a tomato. It's a different species, but it's very closely related to tomato.
PALCA: Yeah. That's great.
Prof. KLEE: You like it?
It's called red currant. It's intensely tomato-flavored and very sweet. Klee will be trying to capture the genes in fruit like red currant and get them into modern, high-yield varieties.
The good news is molecular genetics has speeded up plant breeding enormously. One lab can now do what it used to take thousand of breeders to do.
Prof. KLEE: And with modern molecular breeding tools, I can do that in months, instead of years.
PALCA: In the mean time, if you want a really great tomato, be nice to Harry Klee, and he'll be nice to you.
Prof. KLEE: Try that one.
PALCA: That's very sweet.
Prof. KLEE: Yeah.
PALCA: That's good.
Joe Palca, NPR News. Transcript provided by NPR, Copyright NPR.