When Devin Peterson bit into a Scotch bonnet pepper, he expected fire. What he got instead was something much tamer.
The chili was rated at 800 Scoville units — supposed to deliver a good sting — but the sensation didn’t match at all. Peterson, a flavor chemist at The Ohio State University, knew something wasn’t adding up. For over a century, the Scoville scale has been the gold standard for measuring a pepper’s heat, pegging spiciness to the concentration of two molecules: capsaicin and dihydrocapsaicin. But now, it seemed, some chilies were defying the math.
So began a scientific detective story that would upend what we thought we knew about chili heat — and point the way toward a condiment of the future: the anti-spice.
When Scoville Falls Short
Capsaicinoids — like capsaicin — bind to specific nerve receptors in our mouths. It’s the same receptor that responds to scalding heat or a wasp sting. In other words, spiciness is technically pain rather than flavor. This fiery illusion is what makes spicy food thrilling — or unbearable.
Peterson and his colleagues set out to find out why some peppers taste milder than their Scoville rating suggests.
They began with 10 powdered chili varieties, including the fiery Scotch bonnet, the sharp African bird’s eye, and the citrusy Fatalii. Each sample was analyzed using a method called liquid chromatography-mass spectrometry to precisely measure its capsaicinoid content. Then, the team added equal amounts of these compounds — enough for a mild but noticeable kick of 800 Scoville units — to samples of tomato juice.
Trained tasters evaluated each sample. What they found was that despite identical levels of heat molecules, the perceived spiciness varied dramatically between peppers. Some samples seemed up to 50% less hot than expected.
That was a clear signal. Something else in the chili was modulating the burn.
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Meet the Anti-Spice Molecules
To dig deeper, the researchers performed additional chemical analyses and crunched the numbers. What emerged were three standout suspects: capsianoside I, roseoside, and gingerglycolipid A. These compounds were most abundant in the peppers with unexpectedly low heat.
All three are glucosides — molecules that include a sugar unit. When added alongside capsaicinoids, these compounds dulled the perceived burn without adding any noticeable flavor. A new set of 37 taste testers compared chili-laced tomato juice with and without the mystery compounds, applying the samples to opposite sides of their tongues to ensure a fair comparison.
The anti-spice molecules consistently reduced the chili burn by 0.7 to 1.2 points on a 15-point scale. They are effectively anti-spice compounds. They take the edge off.
Exactly how they do this isn’t fully understood yet. Peterson speculates that the glucosides may interact with the same nerve receptors that capsaicinoids target, altering how they send burning signals to the brain.
Barry Smith, a sensory scientist at the University of London, called the experimental design “very clever” and praised the use of the “half-tongue” testing method. “It shows the Scoville scale isn’t a very precise instrument for describing how hot a chili is,” he noted in an interview with New Scientist.
A New Frontier for Flavor — and Medicine
These anti-spice molecules could help create a new class of culinary tools. Imagine a natural ingredient that lets you dial down a sauce that turned out too fiery — or lets your spice-averse kids enjoy the same food as you.
“Sometimes when I’ve ordered food with my kids and it’s too spicy, that’s a no-go,” Peterson said. “So, the idea of having some kind of a natural compound to dial it back may be appealing.”
In time, growers might even breed peppers with more or less of these compounds to match different taste profiles — hotter, milder, or just better balanced. “Knowing about these anti-spice chemicals could allow growers to breed or genetically modify plants so they lack them to create valuable, even hotter chilies,” Peterson told New Scientist.
The molecules may also hold medical promise. Because they seem to suppress the same nerve pathways that signal pain, they could inspire new, non-opioid analgesics — pain relievers without the risk of addiction.
“This opens up new avenues for pharmaceutical development,” Peterson added. “The discovery of natural dietary compounds that reduce pungency presents promising opportunities for both the food and pharmaceutical industries.”
As with menthol, which cools the tongue through a similar neural trick, future research might explore whether these anti-spice molecules can blunt other sensations as well. Could they, for instance, tame the burn of wasabi or the tingle of ginger?
For now, the humble chili pepper — equally feared and cherished — shows that it can still be full of surprises.
The findings appeared in the Journal of Agricultural and Food Chemistry.