Production of novel varietal hop aromas by supercritical fluid extraction of hop pellets. Part 1: Preparation of single variety total hop essential oils and polar hop essences

Abstract

A new methodology for the selective isolation of varietal total hop essential oil from hop pellets and further chromatographic fractionation of total hop oil into terpeneless polar hop essence, is presented. The methodology is essentially based on supercritical fluid extraction (SFE) of total hop essential oil using carbon dioxide of appropriate density, followed by solid phase extraction (SPE) using octadecylsilica and ethanol/water mixtures for preparation of polar hop essence. Different SFE temperature–pressure combinations were tested for extraction of total hop essential oil from pellets. A carbon dioxide density of 0.50 g/mL (50 °C, 110 atm), proved to be the best compromise in view of selective and quantitative extraction of total hop essential oils. Further fractionation of total hop essential oil by SPE in order to remove hydrocarbons, resulted in varietal polar hop essence, highly enriched in water-soluble, oxygenated hop oil constituents. All of the applied procedures of the proposed SFE/SPE methodology are in full accordance with the principles of clean-label technology. As a result, the novel hop aroma products are fully compatible with the beer matrix. When added to beer, the novel hop oil preparations impart a typical, varietal dependant pleasant hoppy character and increase beer bitterness and mouthfeel.