Why it’s time to retire the Scoville scale for measuring pepper heat



What was state of the art in 1912 has largely fallen by the wayside. Carriages have replaced horses. Washing machines replaced washboards. Air travel, refrigeration and container shipping have transformed the way we live – and that’s before we even got to the internet.

So why, oh why, on God’s Green Earth, do we still measure chili heat on the Scoville scale?

Of all the units that measure all things, the Scoville heat units must be the most antediluvian. This is by no means a diss from Wilbur Scoville, the pharmacist who invented this way of measuring the spiciness of pepper in, yes, 1912. And in 1912, it was genius.

Here’s how it works: Take a chili pepper, dry it and dissolve it in alcohol. Then start diluting it with sugar water. Keep diluting it until three of a panel of five humans – yes, humans – can no longer feel the heat. If you have to dilute one unit of capsaicin-infused alcohol with 10,000 units of sugar water for the pepper’s flavor to be undetectable, that pepper is rated at 10,000 on the Scoville scale.

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It was a great system, because humans are very good at detecting capsaicin.

But they are nowhere near as good as high performance liquid chromatographs.

The heat in peppers comes from a group of chemical compounds called capsaicinoids. The most common is capsaicin, so we usually use that as shorthand for the heat-producing element, but there are many others.

And here’s the thing about capsaicinoids: we can measure them. Without diluting them in gallons of sugar water. Without assembling a panel of humans who have different perceptions of heat and palates that tire quite easily. Detecting capsaicin is absolutely, positively, a job for a machine.

“Humans differ. We vary our taste buds and receptors,” Paul Bosland told me, “but with a machine we can measure very precisely. Bosland, now retired, studied chili peppers at New Mexico State University, and his name is so closely tied to capsaicin that when the school raised $1 million to endow a dedicated professorship looking on the pepper, officials gave him his name. (The gift manager at the school, when explaining that the interest on the money would pay the teacher’s salary, said, “It’s to make sure we’ll have research on Chile forever. “)

The machine in question is this high performance liquid chromatograph (HPLC), which can separate capsaicinoids from the other components of pepper and tell you how many there are in parts per million (PPM). No taste buds required.

It’s no longer a secret in the food industry, where machines are widely used and taster panels are mostly a thing of the past. Although an HPLC will cost you between $50,000 and $70,000, once you have it, the test only costs about $100 per sample, according to Bosland. Try to recruit a panel of five humans for this prize!

Pure capsaicin, in parts per million, is 1 million ppm. One PPM translates to 16 Scoville units, so the scale reaches 16 million. The Carolina Reaper, one of the hottest peppers, comes in at 2.2 million Scovilles, but there’s a whole subculture devoted to growing and eating super hot peppers, so an even hotter variety could happen any day.

For the rest of us, the peppers we’re likely to encounter run the gamut. Jalapeños usually come in between 4,000 and 8,000. Hungarian hot peppers come in between 5,000 and 10,000. Serranos are between 10,000 and 25,000, and habaneros, the hottest peppers with which most of us we are likely to cook, start around 100,000 and can exceed 300,000.

And those ranges are infuriating. You can grow the same type of pepper in the same field and get different levels of heat depending on the environment, weather, and ripeness. If it’s a different cultivar and you grow it in a different location, capsaicin content mayhem! When you’re trying to make a food that’s supposed to taste the same every time, it’s not practical. Makers are used to this, Bosland told me, and will use a combination of peppers to achieve the level of heat they want.

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Capsaicin content doesn’t tell you everything, of course. Peppers also have what Bosland calls a heat profile. “When you take a bite, how quickly does the heat rise? Is there a lag? How long does it last? Where do you feel it — at the tip of your tongue? At the back of your throat? And is it sharp or flat? Pointed is like pins sticking to you, and flat is like a brush on your tongue.

And then there is the flavor. With a very hot pepper, it’s hard to taste after the heat, but the peppers also have fruity, earthy, and smoky flavors. When Old El Paso wanted the flavor of the jalapeño, but not its capsaicin, to mix into its products, Bosland was able to grow a jalapeño without heat – and it won him the 1999 Ig Nobel Prize in Biology, me- he said laughing. (Ig Nobel Prizes, parodies of the Nobel Prizes, reward achievements that make you laugh, think, roll your eyes or scratch your head.)

Now that we’ve covered the basics of peppers, let’s get back to the original question: when we can measure parts per million, why do we still use Scoville heat units? For starters, the food chain actually measures capsaicin in PPM, so what’s the point of converting it to a horse and buggy era scale? Then there’s the fact that by multiplying PPM by 16 to get the Scoville units, you’re making the odds even more counter-intuitive than PPM; 10,000 sounds like a lot, but it’s actually just a little. There must be a better way.

Allow me to offer an alternative. A simple 1-10 heat scale, based on the capsaicin content of chili peppers that most of us come across. Let’s use the habaneros to anchor the high end of the scale (and the super hot peppers can be above 10). Poblanos are a 1. Jalapeños are a 2, and so on, in a simple, perfectly understandable scale based on a number we can measure.

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I thought this was a brilliant and original idea until I went to the Scoville scale website and saw that it breaks down peppers exactly this way.

I believe what keeps this simple 1-10 scale from spreading is the lack of a good name. Scoville was onto something when he decided to name his scale after him, so I’ll take a page from his book. Since I am not getting any younger and opportunities for immortality are rare, I think we should name this scale.

From now on, the heat of the pepper will be measured in Haspels. A habanero is a 10-Haspel pepper. Old El Paso will make sure his salsa rolls at 1.8 Haspels. I will be on the signs in the pepper aisles of all grocery stores. This is particularly appropriate since the Haspels measure a substance that can, in quantity, be quite irritating.

You are with me. I know you are.


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