What do Scoville Heat Units measure?

Scoville Heat Units (SHU) are a measurement of the pungency or heat level of chili peppers and other spicy foods, specifically quantifying the capsaicin concentration, which is the active component that causes the sensation of heat. The Scoville scale was developed by Wilbur Scoville in 1912 to gauge the spiciness of peppers by diluting a pepper extract in a sugar-water solution until the spiciness was no longer detectable to a panel of tasters. The higher the SHU value, the spicier the pepper. This system highlights the relationship between the pungency of the capsaicin, making the understanding of SHU essential for culinary uses as well as for forms of self-defense like pepper spray. The other options do not accurately represent what SHU measures, as they refer to aspects unrelated to the actual heat or pungency of the pepper.