S. Feng (1), Y. Qian (1), M. C. QIAN (1);
(1) Oregon State University, Corvallis, OR, U.S.A.
Technical Session 9 - Hop Flavor and Analytics
Wednesday, June 17
8:30–10:15 a.m.
Fiesta 3,4,6,8
Hops (Humulus lupulus L.) are considered the most important ingredient in brewing since they contribute the characteristic aroma and flavor to beer. However, the chemical compounds responsible for the hoppy aroma have not been well understood due to the complexity of hop composition. With the increased interest in dry hopping and aroma hops in the industry, it is important to understand the aroma composition of hops. The aroma compounds in ‘Centennial’, ‘Citra’, and ‘Nelson Sauvin’ hop varieties were investigated in this study. The hops were extracted with dichloromethane followed by solvent assisted flavor evaporation (SAFE) to remove the non-volatile components. The volatiles were further pre-fractionated on a silica gel column into non-polar and polar fractions. Aroma extract dilution analysis was performed for both fractions. The odor compounds were identified by GC/Olfactometry-MS, retention indices, and two-dimensional GC-MS/olfactometry. Although different hop varieties had different aroma profiles, the compounds with high FD values in all three hop varieties were geraniol, 3-methylbutanoic acid, linalool, vanillin, and myrcene. The isomeric ratio of linalool was further investigated on two-dimensional GC-MS. It was found that the (R)-linalool was dominated in all three hop varieties (92–96%); however, during the beer making process, some of the (R)-linalool were converted to (S)-linalool, which has a much higher sensory threshold. The (R)/(S)-ratio of linalool in some commercial beers were further studied and the (R)-linalool ranged from 80% to 93%. This conversion was minimal during the dry-hopping process.
Michael C. Qian is a professor of flavor chemistry at Oregon State University and chair of the Food and Agricultural Food Chemistry Division of the American Chemical Society (2014). He received his Ph.D. degree from the University of Minnesota under the guidance of Gary Reineccius. Michael’s research interests at Oregon State University cover aroma/flavor chemical/biochemical generation in dairy products, small fruits (blackberries, raspberry, and strawberry), wine and wine grapes, beer, and hops. He has published many research papers, including 12 book chapters and 4 books in the field of flavor chemistry, and is a frequent speaker at national and international meetings. In 2014, Michael was named a Fellow of the Agricultural and Food Chemistry Division of the American Chemical Society.
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