Some things really were better in the good old days. It’s not just nostalgia but scientific fact, for example, that tomatoes used to taste a lot better. Somewhere over the course of the late 20th century, they lost their tomato flavour.

How tomatoes went from a sweet-savoury summer treat to something watery and bland presents not just a chemical and genetic mystery, but an economic and cultural one. When the flavour disappeared, why didn’t consumers rebel, the way they do when soda makers change their formulas and the new version disappoints?

The answer is emerging from the field and the lab. Last week, a group of biologists from the US and China unveiled the results of a multi-year study retracing the former flavour of the popular salad staple. The scientists isolated not just the chemistry of the tomato’s lost taste but the genetics—opening up the possibility of creating the perfect 21st century tomato, one that combines the high yields of today with the taste of yesteryear.

One of the study’s leaders, plant biologist Harry Klee of the University of Florida, said they couldn’t have done it without a large contingent of Chinese colleagues. Tomatoes, he said, are beloved in China which is by far the world’s largest producer. In his travels to China, Klee encountered tomatoes served for dessert, on fruit plates. In this context, the flavour deficiency might stand out more than it does in America, where people eat tomatoes pulverized and seasoned into pizza sauce, slathered in ranch dressing, or wedged into Big Macs.

But Klee sees a trend in America towards appreciation of flavour—from the rise of gourmet coffee and craft beer to the increasing number of heirloom tomatoes found in farmers’ markets. Those have given many consumers a sense of what they have been missing.

The study involved 398 varieties of tomatoes, ordinary and heirloom, and about 100 taste-testing volunteers, he said. The project took years, because people can reliably rate the flavour of only about five tomatoes in a sitting before they get sensory burnout. The researchers analysed the chemistry of the tomatoes and found 13 compounds associated with good flavour.

Why tomatoes used to taste so good goes back to their wild roots as sweet little berries that depended on birds or other animals to disperse their seeds. Tomatoes originated in Central and South America, where native people were cultivating them before the arrival of Columbus and the introduction of tomatoes to Europeans.

The flavour seems to have gone missing in the latter part of the 20th century, said Klee, when growers started to focus on other priorities—especially yield and shelf life. This wasn’t all bad, according to Ann Powell, a biochemist at the University of California, Davis. “It’s hard to put blame on breeders," she said. “They have given us attractive products that are palatable and fairly nutritious year round." They ship well, she said, and can be found almost anywhere—even grocery stores in south central Los Angeles.

But evolution is a trade-off, whether it happens by breeding or natural selection. Back when they were being eaten by birds or grown by small-scale farmers, good taste was essential for tomato survival. When modern growers focused on yield and sturdiness, they inadvertently bred plants with random mutations in genes that don’t influence yield, but do influence the chemistry.

“There’s no feedback to the farmers whether they produce a tomato that tastes like cardboard or one that tastes like an heirloom from your backyard," Klee said. The transformation probably didn’t happen all at once. More likely, one flavour compound disappeared at a time. It happened quietly, not with the kind of fanfare that accompanies a new recipe for fast-food items or soft drinks.

Danielle Reed, a taste geneticist at the Monell Chemical Senses Center in Philadelphia, said the findings open up the possibility of growing big, beautiful tomatoes that ship well and also taste delicious. By retracing how tomato flavour got lost, she said, the researchers showed it didn’t have to be that way.

Klee said the plan is to restore the flavour compounds to produce a better tomato. The biggest challenge, however, is making mass-produced tomatoes as sweet as their ancestors. The sweetness comes from sugars the plant produces through photosynthesis, he said. If a plant makes only four tomatoes, it can pump a lot of nutrition into them. If the same plant is bred to produce 20 tomatoes, it can’t keep up, and so it makes each tomato more diluted.

The most efficient, precise way to make a better tomato would be to take advantage of genetic technology, he said, transferring genes from better-tasting varieties, or using the newer technology known as gene editing. That’s unlikely to happen, he said. There’s too much public resistance to genetically modified foods, despite a green light from a number of scientific panels. Still, people tend to associate genetically modified organisms with large-scale farming and a trend towards diminished taste and nutrition. Some might feel differently about a product engineered to bring something back. Bloomberg

Faye Flam is a Bloomberg View columnist.