The science of better-tasting tomatoes

Dr. Liz Baldwin is on a mission to make the tomato you get at the supermarket taste better. She tells Lynne Rossetto Kasper what makes them go bad, and what you can look for to make sure you're getting the best one.

Lynne Rossetto Kasper: You've been researching the tomato and making a tomato taste good for ten years. Tell me how this began.

Dr. Liz Baldwin

Dr. Liz Baldwin: There was a University of Florida breeder by the name of Jay Scott, and he said, "I really want to get flavor back into my breeding program." Because breeders breed tomatoes for a whole host of horticultural characteristics, they have to have a plant that is commercially viable. It has to have good yield and disease resistance, and they do breed for enough sugar, size, and color, but it's very hard for them to breed for the aroma component, because there's probably four hundred aroma volatiles in tomatoes, of which 20 to 40 play a role in the flavor of tomato.

For a breeder to account for all that, they don't have gas chromatographs to measure them. They don't have sensory panels to see how they make the tomatoes taste, so that's what we do. I partnered with this breeder and we started looking at his advanced lines and selecting them for flavor.

LRK: How do you go about creating a tomato that has all these elements?

DLB: In Florida, we have a spring/summer season which is actually in June, and a fall season that comes in November and December. Down in south Florida, south of Miami, we can get a March season. We would harvest his tomato breeding lines in these different seasons, and we would actually cut them up and have a consumer panel taste them.

I would then take the same parts of the tomato, grind them up, and do chemical analysis for sugars, acids, and aroma volatiles. Then we would select tomatoes that the sensory panelists thought tasted good, look at the chemical components, and he would try to breed tomatoes that contained these chemical components: sugars, acids, and certain volatiles.

Basically, we wanted to increase the fruity floral notes, because volatiles are like a piano, like notes or a chord.  You put several notes together and you get a chord, but you put volatiles together and you get an aroma profile. We wanted to increase those fruity, floral notes, and decrease, slightly, the green, musty notes that are quite prevalent in supermarket tomatoes now.

LRK: You mentioned there were three things that could make or break a tomato.

DLB: Yes. First and foremost is the genetics. The genetics are the breeder's genetic profile, and it has the flavor potential for a tomato. You have to have good genetics.

Secondly, there's harvest maturity. Tomatoes are a type of fruit or vegetable that can ripen after you harvest it. Another example is the banana. This is as opposed to a cherry or a grape, which you have to harvest ripe because they don't continue to ripen after you harvest them. Commercially, in Florida, they harvest the tomatoes green. So they are hard and green, they can make it through the transit chain, perhaps up to New York City, and not arrive as mush. We talk about harvest maturity, and the more you let it stay on the plant, the better it's going to taste.

After harvest, what we call post-harvest, is storage. The temperature at which they store the tomatoes can affect the flavor. If you chill the tomatoes, you decrease their aroma.

LRK: But you have to chill it in some way, don't you?

DLB: You do have to chill it in some way to slow down the ripening. So you can harvest the tomato green. You chill it to slow down the ripening so you can ship it farther and have it arrive intact, although it will damage the flavor.

Or you can harvest the tomato with a little bit of color on it: red color, pink color. Then you know that the ripening process has started inside the fruit. If that happens, the fruit will ripen with better flavor than if the ripening process has not started. The only way you can tell that is if there's a little red on the tomato peel. We call those "vine ripe."

The tomato breeder and I came up with a tomato that the University of Florida released, which is called Tasti Lee, and they do try to harvest that vine ripe. They still have to chill to a certain point, but we've tried to convey to the industry that the less you chill, the better the flavor.

LRK: If you're going to chill a tomato, what temperature is generally used that's still going to maintain the maximum amount of flavor?

DLB: If you chill to 70 degrees Fahrenheit, you'll probably be okay. If you go down to 60, which is what the industry generally does, you start to lose flavor. But if you go down to 40 degrees, like refrigerator temperature, you're definitely going to kill the aroma part of the flavor. Consumers shouldn't put tomatoes in the refrigerator.

LRK: You always hear that for tomatoes and bananas. But tomato won't recover if it's been chilled?

DLB: The jury's out on that. It probably could recover, but then it's ripening quite quickly, so it may not have the time to recover before it overripens.

LRK: So look for that blush of red, even if you're out in the field and saying, "I gotta get these puppies in there because I planted too many."

DLB: It's usually at what we call the blossom end. The stem end is where the tomato is hanging on the tomato plant. The opposite end is called the blossom end, and that's where the flower was initially. That's where you'll see the first sign of pinkening, or red color, coming in, and you'll know that ripening has at least started. The longer the tomato stays on the plant, the better it's going to taste, up until about the pink stage. Then it's not so different between pink and red ripe.