Humulone

Humulone is one of the principal bitter acids found in hops (Humulus lupulus). It belongs to the group known as alpha acids, which also includes cohumulone and adhumulone, and is produced in the lupulin glands of the hop cone. The amount of humulone varies among hop varieties and harvests, and it is a major contributor to the total alpha-acid content that influences beer bitterness.

In brewing, humulone is extracted into wort during mashing and becomes bitter through isomerization during boiling. The heat-induced conversion produces iso-humulones, which are more soluble in beer and provide the characteristic bitter reception. The perceived bitterness of a beer depends on the total alpha-acid content of the hops used, the boil time, wort pH, and other brewing factors.

Humulone and its isomers are subject to oxidation, which can affect flavor stability over time. Proper storage of hops, typically in cool and dark conditions, helps maintain bitterness quality. As a chemical class, humulone is part of the broader role of alpha acids in imparting bitterness to beer, complementing the aromatic contributions of hop essential oils that remain largely separate from bitterness.

The name humulone is derived from the hop genus Humulus, reflecting its primary botanical source. In brewing literature, it is often discussed in the context of alpha acids and iso-alpha acids, which together define a hop’s bitterness potential.