Hop CO2 extract

Hops, hay, wood, a hint of citrus and spice. A light cheesy note appears with age. The total extract tastes bitter and smells warmer than the oil.

Hop CO2 extract has no dedicated standard in the IFRA 51 index.

Myrcene oxidises and polymerises easily; α-acids can break down into branched fatty acids with a cheesy odour on ageing. Store dark, sealed and cold.

Humulus lupulus is a perennial bine; female plants bear cones with yellow lupulin glands holding bitter resins and oil. Cones are harvested in late summer in the northern hemisphere, dried and baled. Major growing areas include Hallertau (Germany), Yakima (USA) and Žatec (Czech Republic).

CO2 extraction uses compressed carbon dioxide as the solvent. Under subcritical conditions CO2 takes mainly the volatile fraction, giving a product called a select extract. Under supercritical conditions it also takes lipids and non-volatiles, giving a total extract. On depressurisation the CO2 evaporates completely and leaves no solvent residue.

Brewing is the largest user of hop CO2 extract, because it retains α-acids, the bittering compounds after isomerisation in the boil. Perfumery uses a tiny fraction of this output.

Hop oil is rich in myrcene and humulene, with ratios that vary by variety. Some varieties carry more farnesene or linalool, giving floral or citrus notes. The CO2 extract keeps heavier components and is slightly more stable than the oil.

In perfumery hop CO2 serves fougère, tobacco, hay and herbal-woody accords. It pairs with clary sage, lavender, cedarwood and leather. Dosage is low because it quickly stands out.

Hop CO2 extract is usually a thick yellow-green paste, sometimes very viscous from bitter resins. The grade for fragrance is often the oil fraction separated from the CO2 extract, which dissolves more easily in ethanol.