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The Scoville Scale: How Hot Is That Pepper?

The Scoville scale measures the spiciness of peppers based on their concentration of capsaicin. That's the active component of chili peppers that produces that familiar burning sensation we feel in our mouths when we eat hot peppers. kbeis/Getty Images

Food historian Dave DeWitt was a chili pepper neophyte when he moved to New Mexico in 1974. Back then, the man now known (at least in certain spicy circles) as the "Pope of Peppers" couldn't tell a habanero pepper from a Hatch. And he couldn't handle either one of them.

When DeWitt sat down with some new friends for a steaming bowl of green chili stew upon his arrival in town ... well, an alarm went off in his head. In more ways than one.

"In New Mexico, hot and spicy is eaten at every meal, just about. So they wanted to burn me out. They wanted to see how much I could take," says DeWitt, who since has written more than 50 books, including "The Chile Pepper Encyclopedia: Everything You'll Ever Need To Know About Hot Peppers, With More Than 100 Recipes," and "1,001 Best Hot and Spicy Recipes: Delicious, Easy-to-Make Recipes from Around the Globe." He's also the founder of Albuquerque's National Fiery Foods & Barbecue Show, which began in 1988. "I was sweating like crazy. I had to learn to appreciate foods that spicy."

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Bringing the Heat

Let's begin with a given: The spiciness of food is entirely subjective. What's an eye-watering mouth-blaster to one may be blah and unsurprising to another. Still, it's helpful, before popping some stray pepper from your local grocer into your mouth, to have an idea of what might be considered spicy and what might not.

That's where the Scoville scale comes in. Named after a pharmacist named Wilbur Scoville, the scale was invented in 1912 to measure chemical compounds — capsaicinoids — that trigger that familiar burning sensation.

At first, the scale was little more than a taste test. Researchers took a sample and diluted it until no "spice" was detected, and measured it from there. The process — called the Scoville Organoleptic Test — had its limits. From New Mexico State University's College of Agricultural, Consumer and Environmental Sciences:

Measuring heat with this technique is still subjective and depends on the taster's palate and sensitivity to the chemicals that are responsible for heat. In addition, there are serious limits on how many samples a taster can handle within a reasonable time.

"It was not scientific by our standards," DeWitt says. "But then, they had nothing else."

Scoville scale
The hottest known pepper to date on the Scoville scale is the Carolina Reaper.
Julie eshaies/Shutterstock

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How the Scoville Scale Works

Now, scientists extract the heat-inducing chemicals and measure their "pungency" by using High-Performance Liquid Chromatography. The relative "heat" is measured in Scoville heat units (SHUs). That stands as the primary means of determining spiciness in food (and the effectiveness, in another use of capsaicin — which is one of the major capsaicinoids — of pepper spray).

A bell pepper, for example, checks in on the Scoville scale at zero SHUs. Chomping down on a bell pepper would not prompt so much as a raised eyebrow or a reach for a glass of water. But that's the absolute bottom of the scale. From there, things get interesting.

Jalapeños, plenty spicy for a lot of people, rate relatively low on the Scoville scale (roughly around 5,000 SHUs). Above those are peppers like habanero, cayenne and Tabasco. For the truly adventurous, there's the Carolina Reaper, considered the hottest pepper in the world. At about 2 million SHUs, the Reaper rates, according to Chili Pepper Madness, somewhere between 175 and 880 times hotter than your garden variety jalapeño.

If you're asking yourself why someone would eat something that hot, it's a legitimate question.

"I think that there's a sort of a psychological addiction going on. And people who do like it hot and spicy tend to eat it constantly. Rarely do they give it up. You don't hear people say, 'I used to eat hot and spicy, and now I'm eating bland again,'" DeWitt says. "They just stick with what they like to death. Spiciness in their food gives them some sort of a thrill."

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Spice and Flavor

After his initial run-in with the green chili stew — after he finished sweating — DeWitt was hooked. He took his newfound interest and became a prolific author. He also now runs Fiery Foods & Barbecue Central, the Burn Blog and the annual Scovie Awards, which judges hundreds of products in 16 different categories. The contest drew 742 entries from 32 states and six different countries earlier this year.

Spices — and chilis overall — have become his life.

"Chili peppers don't necessarily help every single food that's out there," he says. "But I can't imagine some foods without them."

That's not to say DeWitt is necessarily a fan of super-spicy foods and sauces. Some are good, says the Pope of Peppers. Some are not. Personally, he doesn't stray far from the medium-hot end of the Scoville scale.

"There are sauces that are made with oleoresin capsaicin that are transformed into an oily substance ... It's so damn hot, but it has no flavor whatsoever. Well, it has flavor. It's terrible. That's bad hot spicy, in my opinion," he says. "You gotta have flavor. That's the key element that the Scoville scale does not measure. Flavor."

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