What is the Scoville Scale? The Story Behind The Heat

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What is the Scoville Scale?

We all know that chili peppers are hot, but the Scoville scale (sometimes simply referred to as the pepper scale) helps us put a rating to them. That’s the simplest of definitions for the Scoville scale. It’s a numerical heat rating index of peppers running from zero heat (like bell peppers) to ratings in the millions (like the Carolina Reaper pepper.)

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The Scoville scale is actually named after its father, the American pharmacist Wilbur Scoville. Scoville created a simple way to measure the pungency of a hot pepper – its heat level. The Scoville Organoleptic Test is based on the dilution of ground up hot chilies. In numerical form, it answers the question: How many equal parts of sugar water do I need to add to a same-sized part of ground chili pepper until I taste no discernible heat at all?

Wilbur Scoville had a panel of tasters who took the test, sipping these concoctions of chili pepper and sugar water in multiple-day trials until no heat was noticed per pepper type. Yes, they performed these sipping trials until they reached a level where their mouths no longer burned from the ground hot pepper within. Aren’t you glad you weren’t on this team of tasters?

Is the Scoville scale only for fresh peppers?

No. Both fresh and dried chilies are measured on it. Though, dried chilies will always share the same overall range as their fresh equivalents.

It can be argued, though, that dried chilies may tend to the upper end of the range. Why? Most dried chilies are dried in their mature state. That’s (oftentimes) a chili that’s turned red on the vine, though some chilies mature to different colors. Those mature peppers contain more capsaicin (the chemical that creates the heat sensation) since they’ve stayed longer on the vine. So, dried chilies typically have a chance to be technically hotter, even though (and here’s the twist) they may not taste hotter.

The equal parts it took to get to that no-heat moment became the Scoville heat units (SHU) we see today on the pepper scale. For instance, see what it would take to reach this heat level neutralization across some of the most popular chilies:

  • One teaspoon of ground poblano pepper (1,000 to 1,500 Scoville heat units) would take approximately 1,000 to 1,500 teaspoons of sugar water diluted into it to not discern any burning sensation in your mouth when tasting it.
  • Low-medium heat jalapeño peppers (2,500 to 8,000 Scoville units) would take 2,500 to 8,000 teaspoons
  • A medium-heat cayenne pepper (4 to 20 times hotter than a jalapeño) would take 30,000 to 50,000 teaspoons (30,000 to 50,000 Scoville units)
  • Habanero peppers (12 to 140 times hotter than a jalapeño) would range from 100,000 to 350,000 teaspoons (100,000 to 350,000 Scoville units)
  • Super-hot ghost peppers (among the hottest chili peppers, 107 to 417 times hotter than a jalapeño) would take anywhere from 855,000 to 1,041,427 teaspoons of sugar water (855,000 to 1,041,427 Scoville units)
  • The Carolina Reaper (atop the hottest pepper list, 175 to 880 times hotter than a jalapeño) would take anywhere from 1,400,000 to 2,200,000 teaspoons of sugar water to neutralize the spiciness (1.4 million to 2.2 million Scoville units)

And finally, any zero-heat sweet pepper, like a bell or a gypsy pepper, take zero teaspoons of sugar water. So they receive zero Scoville units on the scale.

–> Learn More: What Exactly Is A Scoville Heat Unit?

The heat measurement evolution: High performance liquid chromatography

There is now a high-tech option out there for deciphering the heat of chili peppers. They don’t require the tasting method that Scoville’s original test needed. And that’s a good thing as some of the hottest peppers in the world these days could really drive tasters crazy.

Known as high-performance liquid chromatography (or HPLC for short), this test measures the chemical capsaicin in chilies, which, as mentioned, causes their heat in the first place. But in a nostalgic nod to the heat measuring pioneer Wilbur Scoville, scientists then convert their results back into Scoville units. The simplest way to think of the science is about one part of the chemical capsaicin per one million equals around fifteen total Scoville units.

The weaknesses of the Scoville scale

While we’ve talked a lot of science here, really the measurement of hot chili pepper heat – especially with the original Scoville scale – is a pretty subjective thing. There are aspects that affect the findings enough that different laboratories would sometimes have wildly varying results, sometimes up to a 50% difference on tests.

  • Human subjectivity: The Scoville Organoleptic Test relies on the variability in people’s taste buds. People have varying degrees of spiciness they can take, meaning results would vary from tester to tester. In fact, some mild spicy peppers on the scale can feel more “warm” than “spicy”, to some testers.
  • Where the pepper is grown: Chilies, like other fruits and vegetables, take on the flavors of the earth they are grown from. That means the heat of a certain type of pepper can vary widely based on where in the world it originated and the weather the plant experienced.
  • Variance in the chilies themselves: Like humans, no two chilies are alike. There can be differences in the heat from fruit to fruit, even when all else (soil, climate, etc.) is the same.

Even the HPLC test has questions surrounding its conversion into Scoville units. Some scientists believe that the conversion tends to position the heat of the chilies on the Scoville scale too mildly compared to what a human tester would give.

But still, for measuring something that varies so much, the Scoville scale is as accurate as we need it to be. It helps spicy food fans out there, both new and old alike, determine the heat of all sorts of foods: from chilies themselves, to hot sauces and even gourmet fiery meals. So dive into Scoville’s world of spiciness and experience the heat for yourself.

  • The Hot Pepper List: We break down the heat (via Scoville heat units) and flavors or 150+ chilies, with links to full profiles on each.
  • Our Hot Sauce Rankings: We rank hot sauces by overall taste, heat balance, usability, and collectibility. Search by rating. When possible, we give their Scoville heat unit ranges as well.
  • How To Grow Hotter Peppers: Are you looking to maximize the Scoville range of your chilies in your garden? You’ll want to read this.
  • Does Cooking Chilies Make Them Hotter? What happens when a pepper is cooked? Again, if you’re looking to maximize (or minimize) spiciness, you’ll want to read.
  • Male And Female Peppers: Do chilies have genders? We break down the fact and fiction behind the belief.

UPDATE NOTICE: This post was updated on May 12, 2023 to include new content.
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