Scoville scale more, depending on seed lineage, climate and humidity, and soil composition supplying nutrients. The inaccuracies described in the measurement methods also contribute to the imprecision of these values. "Capsicum" chili peppers are commonly used to add pungency in cuisines worldwide. The range of pepper heat reflected by a Scoville score is from 100 or less (sweet peppers) to over 3 million (Pepper X) (table below; Scoville scales for individual chili peppers are in the respective linked article). The class of compounds causing pungency in plants like chili peppers is called capsaicinoids, which display a linear correlation between concentration and Scoville
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