The scientific search for the essence of a tasty tomato

Scientists are several steps closer to restoring flavour to the supermarket tomato, a once-magnificent fruit turned by commercial pressures into a juicy orb of gustatory cardboard.

Tomatoes gain their flavour from a combination of sugars, acids and aromas, but a new study has examined exactly how different elements influence their taste.

Commercial tomato growers have traditionally focused on producing varieties with strong “aroma volatiles”, compounds which easily vaporise and release fragrant molecules into the air.

It was thought that as well as enticing shoppers with their pleasant smell, the tomatoes with high quantities of these compounds might also taste the sweetest.

But a study suggests that most of the volatiles which occur most commonly in tomatoes contribute very little to how much people enjoy them.

In contrast rarer volatiles which are naturally present in some home-grown tomatoes can have a major impact on the sweetness of the fruit, according to new study.

“With something like a banana, you can identify one volatile compound that you smell and say, ‘Aha! It’s a banana!’ With a tomato, it’s not that simple,” said plant molecular biologist Harry Klee of the University of Florida.
“You can detect 400 volatile compounds in a tomato. People have speculated that maybe 20 are really important, and they need to be orchestrated properly. It’s a little more complicated than we like.”

Klee and colleagues’ latest study, “The Chemical Interactions Underlying Tomato Flavor Preferences,” was published May 24 in Current Biology and represents the latest stage in a decade-long effort to identify the genetic and molecular underpinnings of tomato taste.

Their work could explain why certain variants of so-called “heirloom” tomatoes – which predate the commercially produced types sold in most shops – taste so much better, researchers said.

Increasing the handful of aroma volatiles which make tomatoes taste sweeter could help farmers produce tastier varieties without the need for added sugar, they added.

The scientists analysed the chemicals present in 278 samples from 152 heirloom tomato varieties, and asked panels of volunteers to taste test each one, along with commercially grown specimens, and assign scores for flavour intensity, sweetness and sourness.

Some heirlooms were deemed less enjoyable than supermarket-bought tomatoes, but others packed much more flavour, enabling the researchers to pinpoint the compounds causing the variation in taste.

They identified 12 key compounds for flavour intensity and another 12 for sweetness, including eight which also strongly influenced the overall flavour of the fruit.

Klee said: “Growers are not paid for producing a better-tasting tomato. Growers are paid for producing a large quantity of red objects. I always get asked, ‘Are we raising a generation of people who don’t know how a tomato should taste?’ And I think the answer is largely yes.

“We now know exactly what we need to do to fix the broken tomato. Consumers care deeply about tomatoes. Their lack of flavour is a major focus of consumer dissatisfaction with modern agriculture. One could do worse than to be known as the person who helped fix flavour.”

Source: Wired Science & The Telegraph