The familiar burning sensation caused by spicy foods can be as light as a tingle, to a blistering, sweating, hallucinating rampage. Capsaicin, the irritant alkaloid in chile peppers that sets your mouth ablaze, is traditionally measured in Scoville Heat Units (SHU). Spicy food is all the rage, and has consumers turning up the heat and exploring hotter peppers and sauces. Chefs and operators have followed suit, using ghost, hatch and habanero chiles in sauces for burgers, pizzas, fries and more as demand grows.
Created in 1912 by American pharmacist Wilbur Scoville, the original less-than-scientific test involved extracting the capsaicinoids from a dried pepper, then diluting them with a sugar and water solution. A panel of five brave testers tasted the solution. When a majority could no longer detect heat, the dilution factor was measured in 100s of SHU.
In the 1970s, food technologists who wanted better accuracy (and probably to save their taste buds) began using high-performance liquid chromatography (HPLC). HPLC separates compounds within a solution under high pressure—like a ground pepper mash. Then the capsaicinoid concentration can be determined in parts per million, which is directly proportional to the SHU—approximately by a factor 16.
This means pure capsaicin has a Scoville rating of 16 million, and a chile with a capsaicinoid level of 2,000 parts per million, like the tabasco pepper (Capsicum frutescens), would have a Scoville rating of 32,000.
But there are still two flaws in placing all chiles and sauces on a predetermined Scoville scale: the peppers themselves and human tolerance. Hot, dry weather increases capsaicin production in plants, so the same species of pepper, grown in different conditions, can have significantly different SHU levels. People who eat spicy food on a regular basis, or grew up with more peppers in their cuisine, are going to have higher tolerance for hotter foods. You can’t serve the same gumbo in Nebraska that you would in New Orleans. (No offense to Nebraskans or New Orleanians—y’all have different tastes, is all. Koreans would be laughing in their kimchi at both of you.)
The scale is still a good resource to gauge pepper pungency. Hot sauces, extracts, powders and crystals are ranked by SHU, and those at the top of the scale should only be used sparingly in food—unless you’re making a challenge dish like something somebody would eat on a dare. According to the Daily Mail, the first man to finish an entire portion of “The Widowmaker,” a curry made with 20 Naga Infinity hybrid chiles, started hallucinating from the heat. He had to sign a release first, and the chef had to wear goggles and gloves.
We recommend starting at the bottom of the chart, where you find more flavor than burn, and experimenting with mixing peppers together. You can even build unique sensations in your mouth, as different capsaicinoids have different types of burn.