When it comes to chile peppers, how hot is hot? Visitors to Our Global Kitchen: Food, Nature, Culture can see a chart ranking varieties of peppers by their level of Scoville Heat Units (SHU), a score created in 1912 by Detroit chemist Wilbur Scoville.
Scoville’s “Organoleptic Test” was simple: he mixed an extract of ground-up peppers with sugar water and fed the solution, at increasingly diluted concentrations, to a panel of taste-testers until they could no longer detect the heat. The higher the score, the hotter the pepper, from the benign bell pepper (0 SHU) to the jalapeño (2,500-4,000 SHU) and the Trinidad moruga scorpion pepper (up to a stratospheric 2 million SHU).
The Scoville test is still used by some chile enthusiasts but scientists, producers, and processors commonly use a more precise method. Called high performance liquid chromatography, it helps determine the level of capsaicin, the chemical that gives peppers their pungency.
Together with related compounds, capsaicin serves an important evolutionary function: protecting plants from threatening microbes, animals, and insects. For example, capsaicin targets a pain receptor in mammals and repels predators like deer and mice, whose chewing can destroy seeds. But it does not affect birds, which digest the seeds intact and disperse them widely, boosting the pepper population’s survival rates.
Of course, not all mammal species are deterred by capsaicin’s sting. Archaeological evidence indicates that humans gathered wild peppers as early as 10,000 years ago in the Central Andes. Cultivation began 6,000 years ago, and in addition to eating the fruit, early farmers likely took advantage of peppers’ antimicrobial properties for food preservation.
Humans soon found medicinal applications as well: the Mayas used Capsicum to treat asthma, infections, and sore throats, and the Aztecs used chiles to relieve toothaches. Today, chiles are found in everything from chocolate to beer to pharmaceuticals.
By the way, although seeds are thought to be the hottest part of a pepper, the fire resides in the white inner membrane where seeds attach. Drinking water will not stop hot peppers from burning your mouth because capsaicin is not water-soluble. Milk products offer a better remedy because they contain casein, a substance that surrounds the capsaicin molecules so they can be washed away.
Learn more in Our Global Kitchen: Food, Nature, Culture, open for just one more month, through Sunday, August 11.
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A version of this story appears in the summer 2013 issue of Rotunda, the Member magazine.