Ethanol’s effect on essential oil, terpene, and terpenoid extraction in beer

Hops are added to beer, post-fermentation, to extract aromatic essential oils containing terpenes and terpenoids to increase overall hop aroma intensity. Limited studies have been performed to determine if the extraction of hop essential oil is dependent upon ethanol concentrations typically found in beer. It was hypothesised that, as ethanol strength and hop dosage increased, the extraction of essential oil would increase to a point of saturation. In this study, fractional-four factorial design, Soxhlet extraction, GC/MS-SPME analysis and non-linear kinetic modelling was used to analyse how essential oil and various terpene/terpenoid compounds were extracted with varying temperature, dose, alcohol by volume (ABV), and exposure times. The study found that terpenes and terpenoid compounds myrcene, α-humulene, and linalool oxide, respectively, declined with respect to dosage in an exponential first-order kinetic fashion. It is speculated that the saturation point of essential oil and terpenes/ terpenoids is much lower level than conventionally hypothesied in beer. Ethanol is also speculated to be too weak of a solvent to have a significant effect on essential oil extraction.