Scientists Build Better Tomatoes Through Understanding Chemistry of Taste

 @rpalmerscience on February 16 2013 12:04 AM

Your great-grandfather probably ate better tomatoes than you ever will. Unless you want to shell out extra dollars for heirloom tomatoes, or spend time and money growing your own, you’re probably getting something that tastes like grainy wet cardboard.It wasn’t meant to be this way.Modern breeding technologies have produced a plant that produces a lot of big, bright red fruit at once. That’s good for the farmer’s yield, but it means that the plant doesn’t have the time or resources to put a lot of nutrients into every tomato.The recipe for a tomato of today is just basically “take the old tomatoes and add water,” University of Florida horticulturalist Harry Klee told reporters on Thursday at the American Association for the Advancement of Science annual meeting in Boston.Klee and his colleagues are hoping to rectify the tastelessness of the modern tomato by studying what makes heirloom tomatoes retain their flavor. In one recent experiment, they asked 170 volunteers to taste pieces of the 152 different heirloom varieties grown at the University of Florida, rate the fruits they liked, and characterize them based on flavor profiles and texture. “What we do is figure out what’s in the good ones and what’s in the bad ones, and we come up with a recipe for a good tomato,” Klee said.The scientists take that information as a guide when breeding their heirlooms with commercial varieties, with the ultimate goal being to get a good-tasting tomato with some of the disease resistance and higher yield of a supermarket variety. Although Klee and his colleagues are examining the genes of tomatoes to look for clues to flavor, they breed their plants with traditional techniques, not through genetic modification. One reason for that is cost, but there’s also a bit of a political consideration -- “the atmosphere today with [genetically modified organisms] is kind of poisonous,” Klee told NPR last year.Unfortunately, using traditional breeding techniques means the work takes much longer to bear fruit.A tomato is a curious fruit (and it is a fruit, despite anything the U.S. Supreme Court might say, as reported by Wikipedia). It’s a blend of acids and sugars, a balance of contrasting flavors. But one of the biggest secrets to tomato flavor lies in volatile compounds, which are chemicals that result from the breakdown of various constituents, primarily a class of organic pigments called carotenoids.In their recent study, Klee and his colleagues found that some volatile chemicals increased the volunteer’s enjoyment of tomatoes, independent of how much sugar was in the tomato. Somehow, the volatiles enhances a fruit’s flavor.This finding suggests “a novel way to increase perception of sweetness without adding sugar,” Klee and his colleagues wrote in a paper published last May in the journal Current Biology.Tasting a tomato engages your nose, as well as your mouth and tongue. And the nose actually plays a role at different points in the process. Odors enter your nose through your nostrils as you bring food to your mouth in what’s called “orthonasal” flavor perception. Then, when you chew something, that forces odor-bearing volatiles up through the back of the nose in what’s called “retronasal” flavor perception.To get a better sense of the retronasal experience, here’s an experiment you can try at home with a piece of candy or something else that’s sweet. Plug your nose before you bring the candy up to your mouth, and keep holding your nose shut while you chew and swallow. Then, unplug your nose and you’ll get a sudden rush of sweet sensation, as the volatile chemicals hit your newly unblocked nasal pathways.Those volatile chemicals that persist throughout the tasting experience are what give a tomato -- or a piece of fruit, or a brownie -- a full flavor. So Klee and his colleagues at the University of Florida are hoping they can draw out the volatile richness from certain heirloom strains and put that into their new cross-breeds.Of course, building a better-tasting tomato doesn’t necessarily mean that the consumer will be able to get the full flavor experience. Many of the tomatoes that are grown are processed before they hit the table, subjected to heat that drives off all the volatile chemicals, according to Klee.Klee and his colleagues hope to have some of their new flavorful varieties available to small farmers within a year or so. But getting better-tasting tomatoes out on a larger scale will be challenging. Farmers are paid by their yield, not by how good their tomatoes taste. And economic studies show that consumers are very unwilling to pay extra for tomatoes -- the ideal price for them is around $1 a pound, while heirlooms can approach $5 a pound.“Consumers want food year-round, and a lot of compromises have been made along the way,” Klee said.Meanwhile, if you are buying tomatoes from the supermarket, smaller is better if you’re looking for flavor. Klee recommends Campari tomatoes, which are somewhere in between a cherry tomato and a plum tomato in size. And don’t stick them in the fridge -- that is “the worst thing to do to a tomato,” he said. There are still chemical processes going on inside a tomato that replenish volatiles after the fruit is picked, but refrigeration stops that activity cold.

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