Large numbers and scientific-looking acronyms notwithstanding, Scoville’s method isn’t actually that objective. Even trained tasters have a subjective experience, and the tasting palate becomes accustomed to heat, reducing the effect of further chillies. Today, analytical chemists use high-performance liquid chromatography to detect pungency, and translate the results back into Scoville units.
But is one kind of measurement enough? In a recent paper for the journal Appetite, researchers Ivette Guzmán and Paul W. Bosland identified five different sensory characteristics of chilli peppers: development, duration, location, feeling and intensity. The build-up of sensation, the time that sensation lasts, the part of the mouth in which the heat is felt, and the sharpness or flatness of the heat are all taken into account, along with the intensity, still measured in SHU. The heat of a jalapeño is felt on the tongue and lips, while a habanero delivers its payload at the back of the throat.