Chili peppers famously bring the heat to hot sauces, salsas, curries and many other dishes. And if you’ve ever bitten into food that’s too spicy, you know how much they can burn. But now, it seems that certain compounds tame the flames of some peppers’ taste.

It remains a mystery how the newly identified compounds cut down on spiciness, or pungency. But chili peppers that contain more of these molecules don’t have quite as much kick. These findings could one day help farmers grow and develop new kinds of peppers and even aid in pain relief, scientists say.

A chili pepper’s spice level is often measured with the Scoville scale. This scale is based on two compounds that give peppers their heat. One is capsaicin. The other is dihydrocapsaicin. Peppers that contain more of these compounds rank higher on the Scoville scale.

But even when two peppers have the same Scoville rating, one might taste hotter than the other. Devin Peterson and his colleagues wanted to find out why. Peterson is a flavor scientist at Ohio State University in Columbus.

To investigate, the team ran a series of taste tests. The first involved 10 types of powdered chili peppers. The researchers mixed different amounts of each powder with tomato juice so each blend contained the same amount of spice-causing compounds. As a result, each mix had the same Scoville rating.

The researchers offered their samples to a panel of people who’d been trained to judge spiciness. Panelists tasted each mix and rated how pungent it was on a scale from zero to 15. A zero rating meant the panelist couldn’t perceive any spice. A 15 meant they “can’t imagine anything more intense,” Peterson says.

Despite all the samples having the same Scoville rank, some tasted spicier than others, the panel found. Arbol peppers, the least pungent variety, earned an average 7.1 rating. Fatalii peppers, the most pungent type, averaged an 11.8.

Clearly, the Scoville scale did not fully account for some key ingredient in a pepper’s punch.

Anti-spice substances

Peterson’s group took a closer look at the powdered peppers to see what was going on. They analyzed the peppers’ chemical makeup for compounds linked to pungency.

Five chemicals seemed to make peppers less spicy. All were more abundant in the least spicy pepper than in the spiciest one. “These molecules are tasteless,” Peterson says. “Yet when they interact with taste molecules, they’re suppressing them.”

Another round of taste tests offered more insight into the anti-spice compounds. For this experiment, the team prepped two mixtures. One contained just tomato juice, capsaicin and dihydrocapsaicin. The other held tomato juice, those two spice compounds, plus one of the five compounds that were linked to lower spiciness.

The scientists dripped each mixture onto a piece of filter paper. Panelists put both pieces on their tongues, one on the left side and one on the right. This let them see which tasted spicier. In all, 37 panelists did this test for each of the five compounds.

Three of the five compounds took the edge off the mixtures’ spiciness. One called capsianoside I decreased spiciness by 0.7 points on the 15-point scale. Another known as roseoside brought ratings down by 1.2 points. A third called gingerglycoside A soothed spiciness by 1 point.

Peterson’s group also tried using all three anti-spice compounds together. But that didn’t seem to help much. With the combo, spiciness only dropped by 0.7 points.

The findings appeared in the May 28 Journal of Agricultural and Food Chemistry.

Feel the burn — or not

It’s not clear yet how any of these compounds affect our perceptions of spiciness. They might attach to the same receptors in our mouths that capsaicin does, Peterson says. These receptors let us taste spicy things. If the anti-spice compounds block capsaicin from latching on to the receptors, we might not taste as much spice.

But that’s just one possible explanation, says Jie Zheng. The spice-blocking compounds might bind to a different receptor but still have the same effect. Zheng is a biophysicist at the University of California, Davis School of Medicine. He studies spicy sensations but was not involved in the new study.

“It’s important to know how these compounds work,” Zheng says. “That would be very informative to guide the applications that people may find.”

Some of these applications might include growing peppers to be more or less spicy, Peterson says. Or the compounds might work in an “anti-spice” condiment. If your food is too spicy, you could sprinkle the condiment on your food. That might reduce its heat, Peterson says.

The anti-spice compounds might also work as pain relievers, though this hasn’t been tested yet. Gels containing capsaicin are known to relieve nerve pain. But they can also cause a burning sensation. Adding anti-spice compounds to those gels might allow them to provide relief without the burn, Peterson says.