It was in 1912 while working for the Parke Davis pharmaceutical company that one of their chemists, Wilbur Scoville, developed a method to measure the heat level of a chile pepper. This test is named after him, it’s called the Scoville Organoleptic Test, and it’s a dilution-taste procedure. In the original test, Scoville blended pure ground chiles with a sugar-water solution and a panel of testers then sipped the concoctions, in increasingly diluted concentrations, until they reached the point at which the liquid no longer burned the mouth. A number was then assigned to each chile based on how much it needed to be diluted before you could taste no heat.
The pungency of chile peppers is measured in multiples of 100 units, from the bell pepper at zero Scoville units to the incendiary Habanero at 300,000 Scoville units! One part of chile “heat” per 1,000,000 drops of water rates as only 1.5 Scoville Units. The substance that makes a chile so hot is Capsaicin. Pure Capsaicin rates over 15,000,000 Scoville Units.
The validity and accuracy of the Scoville Organoleptic test have been widely criticized. The American Spice Trade Association and the International Organization for Standardization have adopted a modified version. The American Society for Testing and Materials is considering other organoleptic tests (the Gillett method) and a number of other chemical tests to assay for capsaicinoids involved in pungency. Even so, the values obtained by these various tests are often related back to Scoville Units. Nowadays the High-Performance Liquid Chromatography (HPLC) test is used. In this procedure, chile pods are dried, then ground. Next, the chemicals responsible for the pungency are extracted, and the extract is injected into the HPLC for analysis. This method is more costly than the previous, but it allows an objective heat analysis. Not only does this method measure the total heat present, but it also allows the amounts of the individual capsaicinoids to be determined. In addition, many samples may be analyzed within a short period.
As a result of all these tests, various varieties of chile peppers can be ranked according to their heat or “pungency” level:
0-100 Scoville Units includes most Bell & Sweet pepper varieties.
500-1000 Scoville Units includes New Mexican peppers.
1,000-1,500 Scoville Units includes Espanola peppers.
1,000-2,000 Scoville Units includes Ancho & Pasilla peppers.
1,000-2,500 Scoville Units includes Cascabel & Cherry peppers.
2,500-5,000 Scoville Units includes Jalapeno & Mirasol peppers.
5,000-15,000 Scoville Units includes Serrano peppers.
15,000-30,000 Scoville Units includes de Arbol peppers.
30,000-50,000 Scoville Units includes Cayenne & Tabasco peppers.
50,000-100,000 Scoville Units includes Chiltepin peppers
100,000-350,000 Scoville Units includes Scotch Bonnet & Thai peppers.
200,000 to 300,000 Scoville Units includes Habanero peppers.
16,000,000+ Scoville Units is Pure Capsaicin.