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Heat Check: The Science Inside Your Next Bowl Of Chili


Labor Day is here, which for many people signals the unofficial start of autumn. With that comes seasonal standbys like football, falling leaves — and pots of chili.

But have you ever wondered about how harmless-looking peppers can pack such fiery punch? When you pick up chili peppers at the grocery story, they’re obviously pretty cool to the touch. So where does the heat they pack come from?

Your tongue? Your taste buds?

Well, it’s a little more complex than that. The heat of a chili pepper is not actually a taste. That signature burning feeling comes from the body’s pain response system.

Kris Rau is a researcher at the University of Louisville who studies pain.

“The reason why hot peppers are hot is because there’s this chemical compound called capsaicin,” Rau says. “Depending on how hot that pepper is, you have more of that chemical compound capsaicin.”

Once you pop the pepper in your mouth, the capsaicin floods the pain-sensing fibers on your tongue and binds to and opens up a receptor on the nerve’s surface. That receptor is called TRPV1.

Rau describes it as sort of like a tunnel.

“In this case, when capsaicin binds to the TRPV1 receptor, that channel opens up and you get this influx of positively charged sodium charged ions, as well as calcium ions, that go into this cell,” Rau says. “What that causes, then, is for the cell to depolarize. That triggers then an action potential.”

That’s the electrical signal that travels up your nerve cells, or neurons, to your brain, which performs kind of a mind trick.

TRPV1 doesn’t just to respond capsaicin; it registers temperatures over 110 degrees fahrenheit, too.

“Since it detects high temperatures, it also registers in your brain as something that is very hot,” Rau says. “That’s why your mouth feels sort of a burning sensation.”

This prompts your body to go into damage-control mode. Your blood vessels dilate — maybe causing your face to flush — and, if it was a really capsaicin-packed pepper, you might experience some sweating, too.

Still, it’s often not enough to keep you from taking another bite.