There's a reason so much of the produce sold in the supermarket often tastes like cardboard.

Actually, there are several reasons. Most of them stem from the fact that flavor falls far below the list of what the food industry encourages plant breeders to prioritize when developing new varieties—called “cultivars”—of produce.

When they want to focus on flavor, breeders don't have good tools to quickly test the fruit of thousands of cultivars. In a surprising new paper, researchers from the University of Florida describe a new method for "testing" agricultural products based on their chemical profile.

They also got a big surprise. For over a century, breeders have focused on sweetness and tartness when trying to develop more flavorful cultivars. New research shows that the tried-and-true approach ignores about half of what makes a fruit or vegetable so delicious.

Agricultural scientist Patrico Muñoz, one of the paper's co-authors, told IE that his team determined that in blueberries, for example, "only 40 percent [of how well people like a fruit] is explained by sugar and acid." The rest is explained by chemical substances called volatile organic compounds that we perceive with receptors in the nose, not in the mouth.

That find, and the method they used to get there, could change the future of agriculture.

Untangling the connection between chemicals and flavor

The researchers behind this study focused on dozens of varieties of tomatoes and blueberries, including commercial cultivars sold in supermarkets, traditional varieties more likely to be found at farmers' markets and farm-to-farm restaurants. table, and newly developed strains that have recently graduated from breeding programs.

They had two types of data for each cultivar. First, a chemical profile that details what and in what quantity dozens of chemical compounds are found in its fruit. Second, they got results from consumer panels in which hundreds of real people rated each tomato or blueberry cultivar on measures like how sweet it was and how much they liked it overall.

Combining these two data sets allowed the researchers to find out, for example, how much the ratio of 2-methylbutyl acetate to 1-nitro-2-phenylethane influenced the flavor of different tomato cultivars.

Some of the cultivars in the study are GMOs, but even wild fruits are chock-full of these kinds of chemicals. One reason is that plants, which typically spend their lives firmly rooted wherever their seeds fall, have figured out how to make and use compounds to control the world around them in order to survive and reproduce.

“In the fruits, the plants produce [this type of chemical] to attract animals that are going to [eat the fruit and] spread the seeds,” says Muñoz.

Yes, basically all foods contain tons of chemicals that most people can't pronounce.

When all this data was brought together, the researchers used machine learning to build models aimed at explaining how the chemical composition of a fruit is related to the taste of that fruit.

For some fruits, this relationship is relatively straightforward.

“In raspberries, there is only one compound that is raspberry flavor,” says Muñoz. But the flavor of other fruits and vegetables, including blueberries and tomatoes, is the product of a complex interaction between dozens and dozens of chemicals.

Their model revealed how well the various chemical components correlated with the human tasters' ratings for each of the varieties. Surprisingly, the sugars and acids in the fruits only accounted for about half of the variation in taster preferences from one variety to another.

"That means that during the last 100 years we have advanced in less than half of [the variables] that explain [preferences]," says Muñoz.

Breeders will be able to “test” many more products

Breeders have no direct control over what chemicals are contained in the fruit of a given cultivar. Instead, they influence genes, which code for metabolic pathways that make the compounds that ultimately determine a fruit's flavor. Even with modern technologies, it is an unwieldy process that is typically done on a large scale.

Marcio Resende, another co-author of the study, tells  IE that "breeding still depends largely on field experimentation," just as it has for centuries.

What separates today's breeders from their predecessors are the technologies they use to measure the traits that tell them "which varieties move to the next stage in the breeding funnel," says Resende.

They use tools like drones and autonomous robots to "quantify whatever traits are important" in a process called high-throughput phenotyping, he says. Existing technologies have been up to the task of measuring traits like how much fruit a cultivar produces and what color those fruits are.

Measuring flavor has proven much more difficult because there were really only two options: the breeder could taste the fruit himself or he could assemble a panel of testers. For breeders testing thousands of cultivars, that choice is a huge tradeoff. Sampling is highly subjective and systematic testing of people is expensive.

“If you assemble a traditional consumer sensory panel and bring 100 people into a room… you can't feed 1000 varieties in the same day,” says Resende.

This new research is "a proof of concept showing that we can now build models to do the same thing" by measuring chemicals, he says.

This type of research will never produce a perfect version of a particular fruit. For one thing, taste preferences vary over time and culture. Since machine learning models can only make predictions based on the data they were trained on. The panels in the Resende and Muñoz data were done in the United States, so it is very likely that consumers in other markets have different preferences.