Analysis of hop-derived flavor compounds in U.S. hops

Hops Session
Kiyoshi Takoi, SAPPORO BREWERIES LTD, 10 Okatohme, Yaizu, Shizuoka, 425-0013 Japan
Co-author(s): Yutaka Itoga, Sapporo Breweries Ltd., Sorachi-Gun, Japan; Junji Takayanagi, Takayuki Kosugi, Toru Shioi, and Junji Watari, Sapporo Breweries Ltd., Yaizu, Japan

ABSTRACT: In a previous study, we focused on biotransformation of hop-derived monoterpene alcohols (linalool, geraniol, beta-citronellol, nerol, and alpha-terpineol) and their contribution to the flavor of hopped beer. As a result, beta-citronellol was almost absent in hop and wort and gently increased during fermentation, because of the biotransformation from geraniol to beta-citronellol by brewing yeast. The concentrations of geraniol and beta-citronellol in finished beer could be enriched depending on the initial geraniol content in the wort by using a geraniol-rich hop. As a result of sensory evaluation, we found that there was an additive effect among linalool, geraniol, and beta-citronellol and that the flavor impression became lime-like by coexistence of these three monoterpene alcohols. Therefore, we proposed that geraniol metabolism by brewing yeasts contributes part of the hop-derived citrus flavor in beer. In this study, we compared the compositions of monoterpene alcohols in various hops and found several geraniol-rich hops in U.S. hop varieties. Such compositions were almost not observed in European traditional aroma hops. We suggest that a geraniol-rich profile is one of the important characters in U.S. hops. In addition, we discuss the behavior of geraniol and beta-citronellol under various hopping conditions and other factors influencing the citrus flavor of hopped beer.

Kiyoshi Takoi graduated from Tohoku University with an M.S. degree in agricultural chemistry in 1989 and joined the Brewing Research Laboratories of Sapporo Breweries, Ltd. as a biochemist. From 1989 to 2002, he worked on brewing chemistry and mainly investigated beer foam stability. During 2002–2005, he evaluated the brewing properties of malts and hops using the pilot malting and brewing plants in the Production & Technology Development Center. In 2006, he managed product development in the New Product Development Center. During 2007–2008, he worked in the Frontier Laboratories of Value Creation as a lead research brewer and mainly investigated hop-derived flavor compounds. At present, he belongs to the Value Creation Department of Sapporo and develops new products. He received a Ph.D. degree in agricultural chemistry from Tohoku University in 2011.