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The Scoville scale is a measure of the hotness of a chilli pepper. These fruits of the Capsicum genus contain capsaicin, a chemical compound which stimulates thermoreceptor nerve endings in the tongue, and the number of Scoville heat units (SHU) indicates the amount of capsaicin present. Many hot sauces use their Scoville rating in advertising as a selling point.
It is named after Wilbur Scoville, who developed the Scoville Organoleptic Test in 1912The Journal of the American Pharmacists Association 1912; 1:453-4. As originally devised, a solution of the pepper extract is diluted in sugar water until the 'heat' is no longer detectable to a panel of (usually five) tasters; the degree of dilution gives its measure on the Scoville scale. Thus a sweet pepper, containing no capsaicin at all, has a Scoville rating of zero, meaning no heat detectable even undiluted. Conversely, the hottest chiles, such as habaneros, have a rating of 300,000 or more, indicating that their extract has to be diluted 300,000-fold before the capsaicin present is undetectable. The greatest weakness of the Scoville Organoleptic Test is its imprecision, because it relies on human subjectivity.
Spice heat is now usually measured by a method using high performance liquid chromatography (HPLC) (also known as the "Gillett Method"). This identifies the heat-producing chemicals and weights them according to their relative capacity to produce a sensation of heat. This method actually yields results, not in Scoville units, but in "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. This conversion is approximate, and Tainter and Grenis say that there is consensus that it gives results about 20-40% lower than the actual Scoville method would have given. — "Interlab variation the original Scoville scale could be as high as + / - 50%. However, labs that run these procedures could generate reasonably repeatable results."
List of Scoville ratings
Pungency values for any pepper, stated in "Scoville units," are imprecise, for three reasons:
- They may vary considerably within a species—easily by a factor of 10 or more—depending on seed lineage, climate and even soil. This is especially true of habaneros.
- True "Scoville units" are the result of an organoleptic test, in which the measurements of the same sample can vary by ±50%.
- The modern High Pressure Liquid Chromatography test does not yield Scoville units, it yields "ASTA pungency units." The HPLC test itself can vary by about 12%. These are often converted to roughly equivalent Scoville unit values, but as noted above this conversion itself is imprecise.
When interpreting Scoville ratings, this imprecision should be kept in mind. — "Scoville unit measurements cause errors due to build up of heat, rapid taste fatigue, increased taste threshold, and poor reproducibility. Scott Harris, technical service manager for Cal Compack Foods, Santa Ana, CA is quoted as saying "The coefficient of error is 50% for the Scoville method and less than 12% for the HPLC method."
Footnotes
See also
- Schmidt Sting Pain Index to compare the overall pain of insect stings
External links
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"Scoville scale"