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The heat in jalapeno peppers

The biochemistry of our saliva

 Spanish offers picante for spicy-hot and caliente for the mouth sensation of broiling pizza cheese.
  • Spanish offers picante for spicy-hot and caliente for the mouth sensation of broiling pizza cheese.
  • Image by Rick Geary

Dear Sefior Matthew: Why do jalapeno peppers taste hot? At least we call it "hot.” But since even room-temperature peppers scald your tongue, they're not really “hot,” so what is “hot," anyway? — Robert C., San Diego

“Hot” is just our inadequate shorthand for some complicated and still mysterious biochemistry. When you pop that jalapeno into your mouth and start to chew, you release the plant’s natural alkaloid, capsaicin. In some process not well understood, capsaicin reacts with only certain nerve endings, jolting them into action. They zap their unique message to a spot in your cerebral cortex, which decodes the incoming news and slaps the appropriate label on it — whatever name your culture places on the sensation of having a mouth hill of bees. “Hot” is the common label in English, since capsaicin does produce some of the same skin irritation caused by a burn from fire or scalding food, and the two sensations, to the Anglo brain, anyway, are closely related. The more discriminating Spanish language offers picante (related to “bite” or “prick”) for spicy-hot and caliente for the mouth sensation of broiling pizza cheese or for the average August day in Death Valley. Some Oriental languages offer a range of choices for what English dismisses with the single word “salty.”

Equally mysterious is why humans would voluntarily, even eagerly, consume hot peppers. After all, the capsaicin is in there in the first place to protect peppers from being eaten by animals or invaded by insects. The plant assumes we’ll have more sense than to intentionally put in our mouths something we know will cause watery eyes, a runny nose, scorched mouth, sweating, and intestinal emergencies. There’s a theory making the rounds that the alkaloid actually releases pleasure-inducing endorphins in our brains, thus accounting for the mysterious “chile addiction” that makes you overlook the pain and continue shoveling salsa into your mouth. (But I’ve noticed that “endorphin release” is an increasingly popular explanation for practically every lamebrained, otherwise incomprehensible human activity, from nail biting to marathon dancing, and I’m starting to get suspicious.)

Perhaps the more plausible explanation is the psychological process of sensory habituation, for which there is more scientific evidence. We take that first bite of pepper, and our nerve endings send out their distress signals. In some corner of our brains, we know something’s not right, but we plunge on. Another bite. More sensory smoke alarms go off. We ignore them. After the third or fourth bite, our brains get tired of telling us to spit the stuff out and figures if we’re masochistic enough to persist, it’s done all it can to stop us. Our brains simply ignore the distress signals (or, as some theorize, our fatigued mouth nerve endings stop reacting to the capsaicin). As the “hot” sensation is dulled, we must eat more and more to try to recapture that original thrill. (Could that help explain why salsa now outsells ketchup in America?)

Scientists are also drawing a bead on the explanation for why habitual chile pepper eaters will be unfazed by a jalapeno while the occasional indulger will be knocked on his butt. Our taste perception is, in a way, relative to the biochemistry of our saliva. Spit is a kind of ground zero from which tastes are measured. And inasmuch as our saliva is influenced by general body chemistry, pepper fanciers may have some saliva component that affects their perception of “hot.” More likely it’s a combination of psychological and physiological cues, since nothing (except the occasional Matthew Alice correspondent) is as simple as it appears. But anyway, that’s the latest from the hot-pepper-technology front.

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