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The essential oil fraction of hops clearly plays a significant and important role in their contribution to the aroma of beer, yet the potential role of water-soluble flavor precursors in hops is much less certain. The study presented herein investigated a range of glycoside hydrolysis techniques on the aqueous extracts of “spent” hops obtained after supercritical CO2 extraction of hop pellets. A range of enzyme treatments, acid hydrolysis, and yeast fermentations were compared with each other and against an untreated control by measuring the volatile aroma composition of the spent hop treatments using stir-bar sorptive extraction and gas chromatography–mass spectrometry. In general, the enzyme systems show promise for investigating the broad range of glycosides in hops and offer a similar scale of aglycone delivery as yeast fermentations, whereas acid hydrolysis may offer a relatively quick gauge of total content of glycosidically bound terpene alcohols. Eighteen different hop varieties were examined for glycoside composition using one of the enzyme techniques. Selection was based on their genetic similarity or dissimilarity (pedigree), importance to the brewing community, and input from brewers, hop researchers, and hop breeders. Clear differences were apparent in the terpene alcohols following glycoside hydrolysis across these hop varieties, most notably with Columbus and Centennial hops. However, because of the high usage levels used in this study (50 g of spent hops/L of buffer), brewers are cautioned against overstating the importance of the glycoside fraction to the overall aroma of hops in beer. Keywords: Glycosides, Supercritical CO2 extraction (SFE), Spent hops, β-Glucosidase, Stir-bar sorptive extraction (SBSE)
