Scoville scale Scoville Heat Units can be made by multiplying ppm H by a factor of 15" (modified to a factor of 16 by others). Another source using subjective assessment stated: "Conventional methods used in determining the level of pungency or capsaicin concentration are using a panel of tasters (Scoville Organoleptic test method). ... Pepper pungency is measured in Scoville Heat Units (SHU). This measurement is the highest dilution of a chile pepper extract at which heat can be detected by a taste panel (Bosland et al., 2007)." Since Scoville ratings are defined per unit of dry mass, comparison of ratings between
Scoville scale mouth heat receptors, which vary widely among people. Another weakness is sensory fatigue; the palate is quickly desensitized to capsaicinoids after tasting a few samples within a short time period. Results vary widely (up to ± 50%) between laboratories. Since the 1980s, spice heat has been assessed quantitatively by HPLC, which measures the concentration of heat-producing capsaicinoids, typically with capsaicin content as the main measure. As stated in one review: "the most reliable, rapid, and efficient method to identify and quantify capsaicinoids is high-performance liquid chromatography (HPLC); the results of which can be converted to Scoville Heat Units by multiplying