What is the Scoville Scale? The Story Behind The Heat

What is the Scoville Scale?

We all know that 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 hot peppers running from 0 heat (like bell peppers) to ratings in the millions (like Carolina Reapers.)

The Scoville scale is actually named after its father, Wilber Scoville. A pharmacist by trade (working for Parke-Davis Pharmaceutical Company at the time), Scoville created a simple way to measure the pungency of a hot pepper. The Scoville Organoleptic Test is based on dilution of ground up hot chili peppers. 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?

Wilber 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?

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, 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.

–> Learn More: What Exactly Are Scoville Heat Units?

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 chili peppers which causes the heat in the first place. But in a nostalgic nod to the chili pepper heat measuring pioneer Wilber 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.
  • Where the pepper is grown: Peppers, like other fruits and vegetables, take on the flavors of the earth they are grown in. 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 peppers themselves: Like humans, no two peppers are alike. There can be differences in the heat from pepper to pepper, 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 peppers on the pepper 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 hot peppers 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+ chili peppers, with links to full profiles on each.
  • Our Hot Sauce Rankings: We rank hot sauces by overall taste, heat balance, usability, and collectibility. 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.
  • Are Dried Peppers Hotter Than Fresh? Say, fresh cayenne or dried cayenne? Would one have a higher median heat than the other?

UPDATE NOTICE: This post was updated on April 3, 2022 to include new content.
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