A truly tasty tomato is a wonderful thing. But most of the tomatoes you can buy from supermarkets — while red, ripe and perfect-looking — taste of practically nothing. For a long time, scientists thought the difference between a good and bad tomato was down to sugar and acid concentration, but actually there's more at play.
In fact, it's research from the 1960s which suggested the balance of sugar and acid was all that mattered. Now, a new study, carried out at the University of Florida, suggests that, while sugar or acid are important, what's crucial is the presence of subtle aromatic compounds. What's more, it turns out it that the blend of compounds required for a good-tasting tomato can't be judged by smell alone — and the most important aromatics are what's missing from most supermarket tomatoes.
To work that out, the scientists conducted a giant taste test involving 170 volunteers. The researchers grew 152 varieties of heirloom tomatoes — older, open-pollinated varieties that come in all kinds of shapes, sizes and colours — and also purchased standard tomatoes from a local supermarket. Scientific American neatly summarises the results, which are published in Current Biology:
"In Klee's analysis, the most abundant volatile compounds in a tomato-the C6 volatiles-barely influenced what people thought of the fruit's flavour. When volunteers compared the taste of ordinary tomatoes and mutant tomatoes that were genetically modified to lack C6 volatiles, they could tell the two apart, but they did not have much of a preference for one over the other. In contrast, a less prevalent volatile compound named geranial made a huge difference to tomato flavour. Klee noticed that many of the tomatoes the taste testers preferred contained moderate to high levels of geranial.
"When volunteers tried mutant tomatoes with normal levels of sugar, but low levels of geranial, they did not rate the fruits highly. Geranial, Klee concluded, somehow improves a tomato's overall flavour, perhaps by enhancing the fruit's innate sweetness. Supporting this reasoning, a majority of taste testers in an earlier study enjoyed the flavour of tomatoes engineered to contain lemon basil geraniol, which is related to geranial. Compared with heirloom varieties, standard supermarket tomatoes generally have less geranial and other volatime compounds. 'They're kind of like lite beer,' Klee says. 'Even if all the chemicals are there, they are at lower levels.'"
So, supermarket tomatoes are the light beer of the salad world — and now we know why. It's worth noting, however, that all types of basil actually contain geranial, which is presumably why the two team up so well. If you're desperate, then, a few leaves of the herb should be able to perk up even the worst of tomatoes. [Current Biology via Scientific American]
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