In Scoville’s method, an exact weight of dried pepper is dissolved in alcohol to extract the heat components (capsinoids), then diluted in a solution of sugar water. Decreasing concentrations of the extracted capsinoids are given to a panel of five trained tasters, until a majority (at least three) can no longer detect the heat in a dilution. The heat level is based on this dilution, rated in multiples of 100 SHU.
You are right about the subjectivity of the scale, though. The American Spice Trade Association has an objective test using high performance liquid chromatography. They have graciously provided the data to the public free of charge… just kidding you have to be member (starts at $2,500/yr).
https://exoticchillies.com.au/scoville-scale/
Apologies, it seems that I am in fact mistaken.
You are right about the subjectivity of the scale, though. The American Spice Trade Association has an objective test using high performance liquid chromatography. They have graciously provided the data to the public free of charge… just kidding you have to be member (starts at $2,500/yr).