M-59: Development of the mercury-free analytical method for the quantification of hop-derived thiols in beer

T. KISHIMOTO (1), K. Sasamoto (2), N. Ochiai (2); (1) Asahi Breweries, Ltd., Moriya, Ibaraki, Japan; (2) GERSTEL K.K., Tokyo, Japan


Development of a mercury-free, labor-saving analytical method for the quantification of hop-derived thiols in beer was examined. In the newly developed quantification method, stir-bar sorptive extraction (SBSE; GERSTEL K.K.) with in situ derivatization with ethyl propiolate (ETP), followed by analysis using the triple quadrupole GC-MS system (Agilent 7000C ) with thermal desorption unit was employed. Hop-derived polyfunctional thiols (e.g., 4-mercapto-4-methyl pentan-2-one [4MMP], 3-mercaptohexan-1-ol [3MH], and 3-mercaptohexyl acetate [3MHA]) have a high sensory impact on beer with their extremely low odor threshold values, 1.5, 55.0, and 5.0 ng/L, respectively. In addition to the interest of brewers in these thiols, the conventional analytical method is labor-intensive, hence the number of samples supplied for extraction in a day was limited. Moreover, the existing method uses a regent containing mercury ion, which is troublesome to dispose of. The growing world concern about environmental problems makes the disposal of mercury ion-containing wastes increasingly difficult. The newly developed mercury-free, labor-saving analytical technique showed high accuracy and low detection limits (below threshold value), and the content of hop-derived thiols in samples from the brewing process were easily analyzed.

Toru Kishimoto obtained an M.S. degree from Kyoto University, Japan, with a major in food chemistry in 1999. Also in 1999, Toru joined the R&D Laboratory of Asahi Breweries Ltd. In 2008 Toru obtained a Ph.D. degree from Kyoto University for his research, “Hop-Derived Odorants Contributing to the Aroma Characteristics of Beer.” In 2012 he received the Incentive Award from the Brewing Society of Japan. In 2013 he was named chief researcher in the Department of Brewing Technology, Asahi Breweries Ltd., and chief of the Secretariat, Brewery Convention of Japan (BCOJ).

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