The Scoville Scale (SHU) is invented by Wilbur Scoville, a pharmacologist in 1912, to measure the pungency of peppers and chillies, and generally related to their capsaicin content. However, Nowadays, capsaicin concentrations are determined using more scientific methods, typically High Pressure Liquid Chromatography (HPLC). The direct measurement of capsaicin gives much more accurate results than sensory methods.
Wilbur’s method of measurement (the Scoville Organoleptic Test) is imprecise, due to the use of human testers. Capsaicin is the compound in chili peppers that makes them irritatingly hot. A measured amount of capsaicin oil is extracted from a pepper using an alcohol solution. Five experienced human testers are gathered and sugar water is added to shot glasses of the capsaicin until three out of five panelists can no longer perceive any heat. The Scoville heat unit (SHU) rating is then assigned based on the quantity of dilution.
ASTA Pungency Units
Because the Scoville test is subjective, the American Spice Trade Association (ASTA) uses high-performance liquid chromatography (HPLC) to accurately measure the concentration of spice-producing chemicals capsaicinoids. The value of capsaicinoids is expressed in ASTA Pungency Units, where different chemicals are mathematically weighted according to their capacity to produce a sensation of heat. The conversion for ASTA Pungency Units to Scoville heat units is that ASTA pungency units are multiplied by 15 to give equivalent Scoville units (1 ASTA pungency unit = 15 Scoville units). Even though HPLC gives an accurate measurement of the chemical concentration, the conversion to Scoville units is a little off, since converting ASTA Pungency Units to Scoville Units yields a value from 20 to 50 percent lower than the value from the original Scoville Organoleptic Test.
For Example how to scale the hotness, from Capsicum Extract RDHealthIngredients
- 0.5M SHU Capsicum Oleoresin ≈ 3.3%
- 1M SHU Capsicum Oleoresin ≈ 6.6%
- 6.4M SHU Capsicum Oleoresin ≈ 40%
- 9M SHU Capsicum Oleoresin ≈ 60%
- 16M SHU Capsaicin Crystal ≈ 99%