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The Influence of Yeast Strains and Hop Varieties on the Aroma of Beer
B. Matsche, A. Muoz Insa, E. Wiesen, C. Schnberger, M. Krottenthaler

Hops and yeast are two crucial factors when it comes to beer flavor. Depending on the stage hops are added during the brewing process, they can have a high impact on the final beer flavor. Over 400 flavor active compounds in hop oil have been identified so far. Moreover, there is also a range of complex biochemical reactions catalyzed by fermentation that can largely contribute to the hoppy aroma in beer. Biotransformation of mono- and sesquiterpene hydrocarbons as well as monoterpene alcohols, the effect of enzymes on hop aglycones and the release of odor-active thiols are the main biochemical reactions that have been proven to affect the hop aroma in beer. The influence of two yeast (California Ale Yeast and German Ale/Kolsch Yeast) and two hop varieties (Cascade and Hallertau Mittelfrh) on the final aroma profile was analyzed especially on the content of thiols 3-mercaptohexan-1-ol, 3-mercaptohexanacetat, and 4-mercapto-4-methylpentan-2-one terpenes and esters in beer. All the beers with dry hopping treatment that were analyzed had higher concentrations of 3-mercaptohexan-1-ol and 4-mercapto-4-methylpentan-2-one than the aroma threshold. The concentration of 4-mercapto-4-methylpentan-2-one is mainly dependent on the hop variety chosen and not on the yeast. The results show differences in the concentration of geraniol and citronellol when using two different top fermenting yeast strains.

Descriptors: biotransformation, hop aroma, hops, yeast, thiols

BrewingScience, 71 (May/June 2018), pp. 31-38