J. WEI (1), W. D. Liang (1), W. Lu (2), L. Xiang (3); (1) China National Research Institute of Food & Fermentation Industries, Beijing, China; (2) Xinjiang University, Urmuqi, China; (3) Tianjin University of Science and Technology, Tianjin, China
Technical Session 3 - Hop Aroma
Monday, June 15
8:30–10:15 p.m.
Fiesta 3,4,6,8
Hop aroma was considered as the soul of beer and 12 hop aroma compounds, including terpene alcohols and stereoisomers, in beer and hops were measured simultaneously and investigated using a quick, simple, and economical method based on GC-MS with only one single chiral column. As far as the major terpene alcohols and their stereoisomers are concerned, different sensory thresholds in beer were established between stereoisomers by ASTM679 method. For example, the threshold of R- and S-linalool, R- and S-β-citronellol in beer were 2.60 µg/L, 180 µg/L, 23.78 µg/L, and 7.00 µg/L, respectively. Different biotransformation was also studied for terpineols of hops during fermentation. R-(–)-linalool predominantly in hop was reduced into S-(+)-linalool, (+) and (–) of α-terpineol. Geraniol in hop was reduced into R-(+)-β-citronellol, geranyl acetate, R- and S-linalool et al. Generally, the loss of hop aroma during brewing contributes to evaporation loss during boiling and biotransformation of terpenoids in hop with low sensory threshold into stereoisomers or other terpenoids with high thresholds. In this study, the main hop aroma compounds in different beers, including R-(–)-linalool, geraniol, and R-(+)-β-citronellol, were detected with the ranges of 1.52~144.94 µg/L, 1.18~253.8 µg/L, and 0.64~103.17 µg/L, respectively. At the same time, the utilization rate of R-(–)-linalool was investigated with different adding points as follows: dry-hopping (36%) > whirlpool-hopping (31%) > hopping after boiling (25%) > 10 min of hopping before the end of boiling (5%). The higher concentration of R-(–)-linalool was detected, while the later the aroma hop was added. In addition, different hops have different concentration and utilization rates for R-(–)-linalool, which should also be considered when breweries select aroma hops varieties. Meanwhile, sensory evaluation of hop aroma in the final beer also can’t be ignored.
Jiang Wei is a senior engineer and holds a Ph.D. degree. In 2008 she became a member of the China National Research Institute of Food and Fermentation Industries. She is involved in flavor analysis of alcoholic beverages and raw materials using GC-MS and GC-O-MS, studying brewing technology of specialty beers. Meanwhile, she has performed research on wine authenticity and regional origin with NMR and IRMS. In 2014, she was awarded the first-place prize from the SinoLight Corporation for Science and Technology Progress and the third-place prize from the China Alcoholic Drinks Association for Science and Technology Progress. In 2011, she was named the outstanding employee of the China National Research Institute of Food and Fermentation Industries.
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