The Scoville scale is a measurement of the spicy heat (or piquance) of a chili pepper. The number of Scoville heat units (SHU) indicates the amount of capsaicin present. His method, devised in 1912, is known as the Scoville Organoleptic Test.
The Scoville organoleptic test. In Scoville's method, an alcohol extract of the capsaicin oil from a measured amount of dried pepper is added incrementally to a solution of sugar in water until the "heat" is just 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 hottest chilis, such as habaneros and nagas, have a rating of 200,000 or more, indicating that their extract must be diluted over 200,000 times before the capsaicin presence is undetectable.
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