The Scoville scale is the measurement of the pungency (spicy heat) of chili peppers or other spicy foods as reported in Scoville heat units (SHU), a function of capsaicin concentration. The scale is named after its creator, American pharmacist Wilbur Scoville. His method, devised in 1912, is known as the Scoville Organoleptic Test.
The Scoville scale is an empirical measurement dependent on the capsaicin sensitivity of testers and so is not a precise or accurate method to measure capsaicinoid concentration, however, capsaicin concentration can very roughly be estimated as ~18µg/SHU.
Scoville organoleptic test
In Scoville's method, a measured amount of alcohol extract of the capsaicin oil of the dried pepper is produced, after which a solution of sugar and water is added incrementally until the "heat" is just barely detectable by a panel of (usually five) tasters; the degree of dilution gives its measure on the Scoville scale. Thus, a sweet pepper or a bell pepper, containing no capsaicin at all, has a Scoville rating of zero, meaning no heat detectable.
The greatest weakness of the Scoville Organoleptic Test is its imprecision, because it relies on human subjectivity. Tasters are given only one sample per session. Results vary widely, up to 50%, between laboratories.
High-performance liquid chromatography
Spice heat is usually measured by a method that uses high performance liquid chromatography (HPLC). This identifies and measures the concentration of heat-producing chemicals. The measurements are used in a mathematical formula that weighs them according to their relative capacity to produce a sensation of heat. This method yields results, not in Scoville units, but in American Spice Trade Association (ASTA) pungency units. A measurement of one part capsaicin per million corresponds to about 15 Scoville units, and the published method says that ASTA pungency units can be multiplied by 15 and reported as Scoville units.
Scoville units are a measure for capsaicin content per unit of dry mass. This conversion is approximate, and spice experts Donna R. Tainter and Anthony T. Grenis say that there is consensus that it gives results about 20–40% lower than the actual Scoville method would have given.
List of Scoville ratings
Scoville ratings of chemicals
|Scoville heat units||Examples|
Scoville ratings of peppers
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