Capsaicin and Scoville Scale

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Capsaicin is an alkaloid that produces sensations of heat and pain in mammals. It is colorless and odorless, and protects the plant against pests and plant diseases like fungi. There are different alkaloids, which is why there are flavor variations among different species of chili.

Chilis contain capsaicin (can also be spelled with a k), a compound that adds a sensation of heat when eaten. The capsaicin binds to a receptor called TRPV1, which sends on information to the brain that the temperature is at least 109.4°F (43°C), which in turn provides a sensation of heat in the body. At the same time the capsaicin generates a feeling of pain, which varies depending on the amount of capsaicin in the fruit. The chemical makeup makes capsaicin a fat, which is not water soluble, which in turn explains why it is impossible to cool the heat by drinking water.

Chilis are prized by birds, which have no capsaicin receptors. They don’t feel the heat and so can happily nosh on chils and spread the seeds through their excrement—a smart way for the plant to ensure its propagation. Mammals eating chili risk crushing the seeds with their teeth, so it’s to the plant’s advantage that various mammals think chilis taste bad (the chili couldn’t know that humans were going to appreciate capsaicin).

The capsaicin compound separates chilis from all other fruits and vegetables. Of course, there are other raw foods that taste spicy, but not in quite the same way since they lack this active compound. The chili fruit’s heat strength is measured in Scovilles, a measurement created especially for this purpose.

Scorching Cultivation

Ed Currie, aka Smokin’ Ed, has brought out the Carolina Reaper and a line of other spicy varieties through cross-pollination. He cultivates on his farm in South Carolina, where the climate is humid and subtropical, an excellent combination for growing chilis in garden beds. Puckerbutt Pepper Company is located in the small community of Fort Mills. On his farm, Ed works in collaboration with Christopher Phillips, who collects rare chilis, growing 540 different varieties on approximately 222 acres (90 hectares).

The typical aroma of chili is so dense over the fields that it’s noticeable even indoors. In a barn, newly harvested chilis are stored in big black plastic containers while waiting to be made into powder or sauce. We’re talking a lot of pounds of heat! The chili handlers, who wear protective clothing with gloves and breathing masks to be able to stay in the building, must still walk outside for fresh air now and then. That’s how saturated the air is with capsaicin.

Ed munches on chilis like snacks, but admits that he still feels some heat after the world record holder Carolina Reaper. To him, the taste is like a roasted sweetness, delivered with immediate heat that increases like a tidal wave until it makes you feel like your whole body is burning, producing teary eyes, profuse sweating and flailing arms. The next day, when the chili is eliminated, the butt puckers from the heat, which explains the name Pucker Butt.


Ed’s goal in producing strong chili varieties is driven by his conviction that one day chili will cure cancer and reduce the risk of cardiovascular disease. With this in mind, he donates each year a large part of his harvest to the research department at the University of North Carolina at Chapel Hill.

The meeting between two “chili heads” such as Kerstin and Ed turns into a discussion about varieties, flavors, growing methods, and heat strength. It is also about how to limit your culture. Why stop at 300 or 540 varieties when there are so many more to discover? Kerstin returns to Skåne with (among others) a specimen of Chocolate Bhutlah, which, according to Ed, will be his hottest chili to date.

At the 2017 Chelsea Flower Show in London, Mike Smith, a fruit cultivator from Wales, presented an even hotter chili variety. Dragon’s Breath, as Mike calls it, has registered an average of 2.48 million Scoville units. The origin of this chili is a plant called Infinity, which belongs to the Capsicum chinense, which has measured 1,067,286 Scoville units. An Infinity plant has been grown under strictly controlled conditions as to watering, heat, humidity, nutrients and light, and the fruits are small, similar in size to gooseberries. Mike Smith, just like Ed Currie, hopes that his chili can be useful medicinally—in Mike’s case, as an anesthesia alternative for people allergic to such medications.

Dragon’s Breath still has to be acknowledged as the world’s hottest chili by the Guinness World Records, and according to Mike, there are no plants or seeds for sale—yet.


Breeding Programs in Other Places

The chili fruit is New Mexico’s designated “state vegetable” and it is said that the most common question here is “Red or Green?” Chili was grown here long before it became popular in Europe. As early as in the 19th century, Fabian Garcia at New Mexico State University set about producing new varieties of chilis. New Mexico #9 arrived in 1913, and it’s a variety that, in principle, changed American chili growing method and usage and cleared the way for the chili’s enormous popularity in the country. It’s a mild chili with a flavor reminiscent of fresh onions, a bit sweet and crisp with a hint of smokiness. When it ripens to red, you can also sense some earthiness and more heat. It replaced the traditional Mexican varieties, and what secured its success was primarily its capacity to yield large harvests, which is necessary for agricultural profitability.

Garcia’s milder chili varieties made it possible to develop new areas of usage for chili. This helped the use of chili to spread to all corners of the USA, instead of keeping it a regional harvest primarily grown and consumed by the Spanish-descendant population in the southern states. The chili breeding program continued, with, among others, Paul Bosland, who founded chili’s own research department at New Mexico State University in 1992: The Chile Pepper Institute. Among other things, he has developed mild varieties of jalapeños and habaneros, and lines of decorative varieties, most of which include NuMex as part of their names.


Many professional chili growers emphasize the importance of the growing location for the product’s terroir (area-distinctive) taste. Chili, much like wine, gets its distinctive flavor depending on where it is grown; one important factor is the area’s rock formation. The hobby grower can add minerals like rock flour, basalt rock flour, or Epsom salt (magnesium sulfate) to the pot’s soil and in this way amend the fruit’s flavor.

From Sweet to Searing

Bell peppers have a Scoville Heat Unit Scale (SHU) of 0, and the mildest chili varieties, such as the poblano, come in at 500–1000 SHU. Jalapeños are around 5,000, cayennes 30,000–50,000, and habaneros between 250,000 and 900,000 SHU. Bhut Jolokias are between 800,000 and 1,000,000 SHU. The Carolina Reaper, crowned the world’s hottest chili in 2013, averages heat strength of 1,569,300 SHU, according to Winthrop University in South Carolina, which did the measuring. Guinness World Records confirmed this measurement. One of the fruits measured 2.2 million SHU!


Chilis’ heat is measured in scovilles, or Scoville Heat Units, shortened to SHU. The American chemist Wilbur Scoville developed the measuring scale in 1912, and the procedure started out as a taste testing to decide the strength of the pepper. The scale goes from 0 for bell peppers to 16 million for pure capsaicin. The measurement is derived by using ethanol to extract the chili’s capsaicin, then diluting the extract with water until there is no longer any chili flavor. The more the capsaicin is diluted, the hotter the chili. The Scoville reading is 50,000 if you dilute the capsaicin 50,000 times.

Nowadays laboratories use a more accurate measuring tool called HPLC. The abbreviation stands for High Performance Liquid Chromatography. It entails drying the chili fruit and milling it to a powder that is then measured for capsaicin content by the instrument. The HPLC can also find the different types of capsaicinoids in the chili. The HPLC method is considerably more expensive, and far from all chilis have been tested this way.

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Excerpted with permission from Chilis: How to Grow, Harvest, and Cook with Your Favorite Hot Peppers, with 200 Varieties and 50 Spicy Recipes by Kerstin Rosengren and Eva Robild. Copyright 2019 by Skyhorse Publishing, Inc.

Mother Earth Gardener
Mother Earth Gardener
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