Research: The Pepper Heat Index

People are always competing to set some extreme record or other. Who’s built the tallest building? Who can swim the farthest? Who can live the longest? Competitions are not confined to the human race, though. For example, every time we think we’ve discovered the hottest pepper on Earth, another upstart comes along to set an even more painful fire on our tongues. In the past few years, the Ghost Chile, the Naga Viper, the Trinidad Scorpion Moruga, and the Carolina Reaper have all held the coveted title of Hottest Pepper. There are so many different types of pepper, though. Where do they all fit in? And how do we go about comparing heat levels from pepper to pepper?

Until recently, the traditional method has always been the Scoville scale, named after a test that Wilbur Scoville devised in 1912. That scale measures Scoville heat units (SHU), which is a function of capsaicin concentration in each pepper. Way down at the bottom are our friends the bell peppers, which have a SHU of zero. Then come the milder zings like paprika and pimiento, which won’t crack a SHU of 1,000. In the 1,000-3,500 SHU range, you’ll find Pam’s and my current pepper of choice, the poblano. Jalapeño is the level above that, in the range that goes up to 10,000 SHU.

From 10,000-30,000 SHU, you’ll find serrano peppers and peperoncino. Cayenne and tobasco peppers lie in the 30,000-50,000 SHU range, while 50,000-100,000 SHU contains lesser known peppers, such as piri piri and malagueta. My painful experience with habanero makes sense, because it shares the 100,000-350,000 SHU range with Scotch bonnets. A specific type of habanero called “Red Savina” lies between 350,000-580,000 SHU, but even that pales in comparison to the peppers I mentioned in my opening paragraph. None of those peppers is less than 855,000 SHU.

All that SHU measurement is nice, but there’s a fatal flaw in the Scoville scale. It’s completely subjective, which I was shocked to learn. Decreasing concentrations of the extracted capsinoids are given to a panel of five trained tasters, until a majority (at least three) can no longer detect the heat in a dilution. OK, but... People’s taste buds differ from each other, and even on the same tongue, a taster’s receptors can be worn out or overused with multiple tastings, changing the results. Can you imagine if the official daily temperature was taken by people wandering outside and saying “Eh. It feels like it’s about 56° F today.”

Fortunately, these days, there’s a system that’s a lot more scientific. Using high-performance liquid chromatography, it can be determined how many parts-per-million of alkaloids (the heat-causing agents) are present in any given pepper.

Tastes in pepper heat vary across cultures (Asians seem to favor a sharp punch of heat at the beginning, while Americans favor a lower heat that sustains for a longer period of time), and some people have made it a personal mission to find the upper limit of what their taste buds can handle. I’ll leave all that record-grabbing to them, and just enjoy the gentler wallop of a dish spiked with cayenne.