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It’s not sugar that makes heirloom tomatoes taste sweeter

Posted on behalf of Alice Lighton.

Photo by Mark Taylor

Researchers have answered a question that has bothered gastronomists for years – which is the tastiest tomato? At the same time, they discovered a heady mixture of volatile organic compounds that gives tomatoes a sweeter flavour than their sugar content would suggest.

In addition to the uninspiring perfect red spheres on supermarket shelves, there are hundreds of heirloom varieties, such as the Mexican Midget and Mr Stripey, that come in all shapes, sizes and colours. Aficionados swear by the wonky fruits, which were bred before mass farming methods arrived.

“People don’t generally like tomatoes that come from supermarkets,” says Denise Tieman, from the University of Florida. The researchers selected about 50 heritage species which they liked the taste of and grew well in the Florida sunshine.

To find out what makes heirlooms so good, Tieman and her colleagues analysed the volatile organic compounds in heirloom and supermarket tomatoes, and asked volunteers to rate varieties based on their deliciousness and intensity of flavour.

According to their study, published in Current Biology, certain volatiles enhance the inherent sweetness in the fruits. Tomatoes with high content of a particular apocarotenoid tasted sweeter. Previous studies have shown that consumers don’t like fruits with low quantities of apocarotenoids.

The compounds could be used as a sweetener, allowing manufacturers to reduce the sugar content of processed foods. “If the food industry wanted to use these compounds, they’re available,” says Tieman.

The complexity of the interactions between chemicals in the tomatoes is borne out by the finding that one of the strongest odours in the fruit is irrelevant to the eater’s enjoyment. Tasters could differentiate between a normal tomato and a genetically engineered tomato with a class of chemicals known as C6 volatiles removed, but savoured both equally.

The Florida team is now breeding tomatoes that produce more apocarotenoids to look for a genetic link to flavour. Meanwhile, in the experiment’s fierce competition for top tomato, the supermarket varieties came off badly. The winner, by quite a margin, was the small, sweet Cherry Roma.


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