The Scoville Scale and the Scoville Spicy Unit (SHU) were named after the scientist Wilbur Scoville in 1912. Scoville was then working for the pharmaceutical company Parke-Davis, where he developed a test called the "Scovill Taste Test" to measure pungency and spiciness chili.
First, Scoville ground dry chilies, prepared their extracts and mixed them with fresh water, and then tested them with a group of tasters who tasted the prepared solutions.
He then successively diluted the solutions several times until most tasters no longer perceived the spiciness. He then assigned a number to the chili based on the number of dilutions needed to negate the spiciness.
The Scoville scale can be used not only to measure chilies, but also anything made from chilies, such as hot sauce. Tabasco sauce is rated at around 5000 SHU. What exactly does that mean? According to the Scoville scale, it would take as many as 5,000 cups of water to dilute 1 cup of sauce to the point where you no longer feel the spiciness.
Pure capsaicin, which makes chili peppers hot, is rated at an incredible 15-16,000,000 Scoville hotness units. The term "capsaicin" comes from the classification of pepper plants in the genus Capsicum.
Capsaicin occurs naturally in peppers together with other capsaiciniodes, which, depending on their mutual relationship, form the unique sensations of spiciness of different types of chilies.
Testing chili spiciness is no longer so subjective. Human taste buds have been replaced by advanced instrumental analysis methods that accurately measure the capsaicin content of chilies and convert it into traditional Scoville units.