What is SHU?
The Scoville scale is a measurement of the pungency (spiciness or “heat”) of chilli peppers and other substances, recorded in Scoville Heat Units (SHU). It is based on the concentration of capsaicinoids, among which capsaicin is the predominant component.
The scale is named after its creator, American pharmacist Wilbur Scoville, whose 1912 method is known as the Scoville organoleptic test. The Scoville organoleptic test is a subjective assessment derived from the capsaicinoid sensitivity by people experienced with eating hot chilis.
An alternative method, High-Performance Liquid Chromatography (HPLC), can be used to analytically quantify the capsaicinoid content as an indicator of pungency.
Scoville Ratings
Since Scoville ratings are defined per unit of dry mass, a comparison of ratings between products having different water content can be misleading. For example, typical fresh chilli peppers have a water content of around 90%, whereas Tabasco sauce has a water content of 95%.
For law-enforcement-grade pepper spray, values from 500,000 up to 5 million SHU have been reported, but the actual strength of the spray depends on the dilution.
Capsicum Peppers
Capsicum chilli peppers are commonly used to add pungency to cuisines worldwide.
The range of pepper heat reflected by a Scoville score is from 500 or less (sweet peppers) to over 1.5 million (Carolina Reaper)
SOURCE: Wikipedia