NOVA

(instrumental music) To learn more about molecular locks and keys, I've come to experience them viscerally. (crunches) (laughing) Oh, wow! Here at the Berks Pepper Jam, in Bethel, Pennsylvania. Smell that. -

Narrator

An annual festival of food, entertainment, and contest, all centered on chili peppers. Reaper Evil Hot Sauce. They do have an ambulance on hand, right? They do. When it comes to peppers, I'm a novice. But the first thing you need to know, is that the black pepper you see sitting with salt and chili peppers, have different chemistries and histories. Black pepper is the dried ground-up fruit of a flowering vine native to Asia. Its kick comes mainly from the molecule, piperine. While one side of the world had black pepper, the other side had chili peppers. First domesticated by Mesoamericans, and then traded around the world by European explorers. The main active ingredient in chili peppers is the molecule capsaicin. More on that in a bit. Three, two, one, eat. The jam features a pepper-eating contest for kids. But they wouldn't let me in. So I plan on entering the one for adults, after I get some advice. I've actually never eaten a pepper by itself. Bow out when you feel you should. Really? Raw pepper is a completely different deal. I can't do it. -

Narrator

You can't eat a reaper? Is there any way I can prepare? No. - You got your will made out? You don't have anything to do for the next three days, do you? -

Man 1

Yeah, you're gonna feel great Monday morning. (men laughing) A big round of applause for Lizzie, well done. -

Narrator

Time to put my tongue to the test. -

Man 2

Long hots, red fresno. -

Narrator

Here's how the contest works. There are ten rounds of increasingly hot peppers. Peach copenhagen, big red mama. -

Narrator

Their spiciness measured on a scale, invented in 1912, by pharmacist Wilbur Scoville. It estimates the amount of capsaicin in each pepper. Contestants have to eat a pepper, and then wait two and a half minutes to allow the burn to grow. If they drink the milk in front of them, a popular way to douse a tongue on fire- They are eliminated. -

Narrator

They're out. My competitors include some rugged-looking characters, and Leah. I've never done this before, I figured this out two hours ago. -

Narrator

a 15-year-old, who entered with the permission of her parents. (crowd cheering) -

Commentator

We begin our contest with the long hots. Let's turn up the heat, eat. And we're off. Zesty, with just a hint of poison. -

Commentator

Round two, we're gonna start with the red fresno pepper. Eat, eat, eat, eat, eat, eat, eat, eat-- Gotta be some easier way to learn about molecules. -

Commentator

Alright, are we ready? Eat. That was not designed for human consumption. -

Commentator

Round number four, habanero peppers. (crowd cheering) Parts of my body I didn't know I had are on fire. -

Commentator

Ten more seconds, you got this. No I can't. -

Commentator

Don't, no don't do it, no. (crowd shouting) The orange copenhagen pepper, eat. What am I doing? (pepper crunching) Oh man, oh my God. (narrator choking) -

Commentator

Don't do it. I want it! Wherever you are, Scoville, I hope you rot! Cheers! Oh no! So I'm the first to fall. Thank you. Is there a Porta Potty? But there's a bigger mystery. How does a pepper's capsaicin convince my mouth it's on fire? Not recommended. I think I'll find the answer here at Penn State University's Department of Food Science. We all study food so you've got psychologists and microbiologists and engineers. I'm here to see John Hayes. He knows a thing or two about the active ingredient in these So when you went and tasted them, what did you experience? Oh, man, my gut twisted, my tongue burned, my flesh burned, I cried, I got red, my nose ran. It's like putting your tongue on the stove and leaving it there. That was an aversive response. This plant has evolved a chemical called capsaicin. And the reason it makes that is to keep animals from eating the chili pepper. Oh man, the chili festival people never got that message. And we're just a really stupid species? Exactly, we're one of the only species that learned to like that sensation. Ultimately, pepper plants are playing a pretty good trick on humans as well. Capsaicin really is a key ingredient. It has a long, spindly tail attached to a ring. That ring end fits into a specific receptor that's expressed all over your body. Not just our tongue? Not just your tongue. Oh, man. This receptor, this lock, is actually a heat pain sensor. Normally, the receptor, called TRPV1, activates when it comes in contact with something over 106 degrees. The result is a pain message to the brain, "Ouch! Something's hot." It's a warning signal to tell your body danger. -

Narrator

And here's the tricky part. When you eat peppers, those capsaicin keys fit into the heat pain receptors in your mouth, altering their sensitivity. And so, what the capsaicin does is it fits into this molecular thermometer and it lowers the temperature at which it activates it. Like a changed thermostat, they now activate at body temperature, sending a false signal that's identical to the one your brain would receive if you ate something literally burning hot. It lowers the temperature at which we feel burning pain... Yes. But it's not actually burning us? Correct. I'm not gonna see scar tissue? No. No matter how hot it is, it's all a fake-out? Absolutely. -

Commentator

Up next, the yellow seven pot pepper. -

Narrator

Back in Bethel, the pepper-eating contest is entering its final rounds. -

Commentator

Eat! That was warm. Oh, it's burning now. I'm trying to think of a happy place. I can't find one. Evidence that capsaicin's working on the molecular locks of everyone's heat pain sensors is easy to see as they eat a big red momma, rated at over a million Scoville heat units. -

Commentator

Don't tap out now! Don't tap out! -

Narrator

One more falls. We are down to the final four. I'm ready to leave. I can't abuse these people anymore. -

Narrator

This time, the organizer adds concentrated pepper extract. (soft music) How long can this go on? Then, suddenly a resolution that no one saw coming. Ooh! Leah beat 'em! (crowd applauding) Big round of applause, big round of applause. Leah, I am not worthy. You rock! What does a woman with that kind fortitude and strength want to be when she grows up? A fighter pilot. Why am I not surprised? (upbeat music)