Cohumulone is one of the alpha-acids of hops, the fraction responsible for the bittering action hops bring to beer. Brewers track it because not all alpha-acids behave alike: higher cohumulone levels are associated with a harsher, less refined bitterness, so hop breeders select varieties with favourable alpha-acid profiles. During the boil, cohumulone isomerizes into bitter iso-alpha-acids that dissolve into the wort. Its measurement, alongside total alpha-acids, helps brewers predict bitterness units and keep the beer’s bite consistent from batch to batch.