Systematic Analysis of Behaviour of Hop-Derived Monoterpene Alcohols During Fermentation and New Classification of Geraniol-Rich Flavour Hops

Abstract

In this study, hop-derived monoterpene alcohols (linalool, geraniol, β-citronellol, nerol, and α-terpineol) and their behaviour during fermentation have been focused on. Total 42 hop varieties were compared. As a result, it was suggested that a group of geraniol-rich ‘Flavour hop’ varieties, which could generate a large amount of β-citronellol to finished beer, could be furthermore classified into two types, ‘free geraniol dominant hops’ and ‘geraniol precursor dominant hops’. ‘Free geraniol dominant hops’ mainly contain free geraniol at high levels and subsidiary geraniol precursors. Most of ‘geraniol-rich hops’ was classified into this type, for example Motueka, Bravo, Cascade, Citra, Mosaic, Sorachi Ace, 0612B and so on. ‘Geraniol precursor dominant hops’ might mainly contain geraniol precursors at high levels and subsidiary free geraniol, for example, Vic Secret, Comet, Hallertau Blanc, Polaris, Amarillo, HBC366, and Summit.