Feel the Burn (Don't Taste It)
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Love it or hate it, you know the sensation of biting into spicy salsa: the burn, the rush, the sudden sweats (or eye-watering or nose-running). Behold, the power of capsaicin!
Capsaicin is the compound responsible for chile’s spicy heat, technically called pungency. Peppers of the capsicum genus produce it in varying amounts to ward off nibbling insects and mammals, for whom it’s an irritant. Birds, however, lack the protein receptor needed to perceive it, so they feast away and spread seeds in the process. Win-win!
Also a win: us humans breeding different chile varieties to get just the right level of burn for our favorite recipes.
And it is in fact a burn, not a flavor. Capsaicin doesn’t trigger the gustatory receptors in our taste buds—the ones that produce familiar tastes by detecting the ions H⁺ (sourness) and Na⁺ (saltiness), or molecules like sucrose (sweetness), caffeine (bitterness), or glutamate (umami). It doesn’t even trigger the olfactory receptors way up in the nasal cavity that sense countless aromas and give food its complex flavors.
What does capsaicin trigger? Basically, pain. And it’s not limited to your mouth or nose; any flesh can experience it, anywhere on your body. If your fingers sting after handling jalepeños or (God forbid) you splash sriracha sauce in your eye, that burn on your skin is the same burn you “taste” on your tongue as you eat chile.
This is because the capsaicin molecule bonds with the protein TrpV₁, a receptor in neurons whose main responsibility is detecting excessive temperatures or acidity. Whether you’ve touched something hotter than 104-109°F (40-43°C), come into contact with a strong acid, or just swallowed some extra-hot pico de gallo, TrpV₁ responds the same way: it temporarily opens channels in the cell membrane that allow positive ions to flood into the neuron, particularly Ca⁺². This wave of calcium cations prompts the nerve to cry foul, sending specific pain signals up to the brain that you perceive as a burn.
In other words, capsaicin activates the same neural receptor as actual high heat, producing the same sensation. That explains why we instinctively describe chile as “hot” and “burning.”
But we avoid touching stovetops and playing with acid—burns are bad, right? Why do we deliberately load up our enchiladas with chile’s capsaicin and relish its physiological effects?
Well, one of the brain’s responses to pain is the release of endorphins, neuropeptides that inhibit pain signaling and have the happy side effect of inducing mild euphoria. Between that mental thrill and the other savory flavor compounds present in peppers, you’ve got yourself quite a dining experience. Some people even claim that chile is addictive, though it’s not a physiological hook so much as a psychological affinity. And since they’re low-calorie and rich in vitamins A and C, there’s no harm in frequent indulgence!
Of course, the endorphin buzz will only get you so far if you’ve taken a bite with extra hot sauce and suddenly feel like your face is on fire. You’ll find relief once the capsaicin is washed from your mouth, but that’s easier said than done. Thanks to its lipophilic hydrocarbon tail, capsaicin molecules can slip through your cells’ lipid membranes, penetrating several layers into your tongue, cheeks, and throat. Once it’s in, it really lingers: since it isn’t water soluble, your saliva doesn’t have much of an effect and swigging water won’t help. Capsaicin does, however, dissolve in fats and alcohols, which is why a glass of milk, a scoop of sour cream, or even a well-swished shot of tequila are your best bets for clearing it out and cooling off.
If your fatty drinks and sides are close at hand, you’re all set to dig into your extra-hot salsa and feel the burn. Endorphins await, so go ahead and keep it spicy.
This post was brought to you by Dr. Fred Senese, Professor of Chemistry at Frostburg University; “TRPV1: Pain, Peppers, and Prostaglandins” by Tom Brock, Ph.D.; and a green chile salsa so spicy it brought tears to my eyes.
