Courtesy of Curiosity.com:
“Some like it hot. And some don’t. And whichever camp you fall into, you may have heard of a little thing called the Scoville Heat Scale. Almost every pepper has a massive number attached to it, and the higher the number, the spicier the bite — the spiciest among them boast something like 2.4 million Scoville heat units (SHU). But what does that number even mean? Let’s find out.
The mildest jalapeños rate 2,500 SHU, the spiciest of them weigh in around 5,000. Roast it over smoke, and you’ll get a chipotle pepper, which runs from about 5,000 to 10,000 SHU. A little higher up the scale are chiles de árbol, which start at 15,000 SHU and get as hot as 30,000. And then there are habaneros, which score 100,000 SHU on the low end. That’s about as hot as we personally can manage. But those are a lot of numbers — and very large numbers. Why not something simpler, like a 100-point scale with bell peppers on one end and Carolina reapers on the other?
The most obvious answer to that is, if you set an upper limit on the spiciness scale, somebody is immediately going to breed a spicier pepper. The more exact answer is that those numbers aren’t arbitrary. The Scoville scale tells you what ratio of pepper-to-sugar-water you would need if you wanted to nullify the spiciness of the pepper. In other words, if you ground a mild jalapeño into a mash, then you would need to add 2,500 teaspoons of sugar water for every one teaspoon of jalapeño mash if you wanted to outweigh the heat of the pepper.
Now, why anybody would actually want to do that is beyond us — why eat peppers if you don’t want to experience the heat? But even more troublingly, it makes us think of those peppers on the super-hot end of the scale. What poor sucker got stuck with taste-testing spoonful after spoonful of devilishly hot Dragon’s Breath peppers, adding progressively more sugar water each time until they finally maxed out at a ratio of 2.4 million to one? The answer is: (drumroll, please) nobody. Things work a little differently nowadays.
The good news for hot pepper professionals is that we have found a way to use technology to estimate exactly what that ratio should be. A technique known as high-performance liquid chromatography is capable of analyzing the component parts of a liquid substance, and it can be used to measure the exact amount of capsaicin in the pepper.
That means that the way that modern hot sauce experts calculate a Scoville rating is a bit backward — they start by divining how much spiciness is in the pepper, and from there work out how much sugar water they’d need to cancel it out. So when they breed a 4.5 million SHU pepper next year (and name it something like “Lucifer’s Lace Bonnet”), nobody is going to have to down 4.5 million tablespoons of sugar water.”