Koji Takazumi (1), Takeshi Kaneko (1), Koichiro Koie (2), Takeshi Nakamura (1), Kiyoshi Takoi (3); (1) Frontier Laboratories of Value Creation, Sapporo Breweries Ltd., Yaizu, Japan; (2) Bioresources Research & Development Department, Sapporo Breweries Ltd., Kamifurano, Japan; (3) Product & Technology Innovation Department, Sapporo Breweries Ltd., Yaizu, Japan
Polyfunctional thiols are important compounds for the characteristic aroma of hops. Many researchers are interested in polyfunctional thiols, because of their characteristic flavors and very low thresholds. However, the thiol content of beer is extremely low, and it is very difficult to analyze such low-level thiols. Moreover, the conventional analytical method uses a harmful reagent that contains a mercury compound. In this study, we developed a new method for quantitation of polyfunctional thiols without mercury compounds and applied the method to investigate their contribution to the characteristic aroma of “flavor hops.” First, we developed a new thiol-specific extraction method using a silver ion fixed SPE cartridge. Then we employed it and gas chromatography-tandem mass spectrometry (GC/MS/MS) with selected reaction monitoring (SRM) mode for quantitation of polyfunctional thiols in hops and beers. The method has sufficient sensitivity and also has good apparent recovery and repeatability and allows us to analyze eight samples per day. Next we investigated more than 30 varieties of hops and 6 polyfunctional thiols. 4-Methyl-4-sulfanyl-pentan-2-one (4MSP) and 3-sulfanyl-4-methyl-pentane-1-ol (3S4MP) were present in wide varieties and, thus, were considered important thiols for brewing. 4MSP was especially high in Citra, Mosaic, and Simcoe varieties, and 3S4MP was high in Halltau Blanc, Nelson Sauvin, and Mosaic varieties. Finally, we evaluated the contribution of these thiols to the aroma of beers brewed with Citra and Nelson Sauvin by sensory analysis using model samples simulating the compositions of flavor compounds in test beers. As a result, we revealed that these thiols are very important for characteristic aroma derived from these “flavor hop” varieties.
Koji Takazumi received an M.S. degree from the Department of Agriculture, Hokkaido University. He began employment with Sapporo Breweries, Ltd. in 2002 as an analytical chemist in the Frontier Laboratories of Value Creation. His current research focuses on hop-derived flavor compounds.