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Influence of hop fraction on the quality of adjunct beer

This presentation reports the results of investigations into the impact of the form of hop fraction on the quality (flavor, taste, and bittering quality) of adjunct beer (60% malt and 40% corn syrup). The forms of hop fraction examined were T-90 pellets, CO₂ hop extract from T-90 pellets, and spent hops (hop residue from the manufacturing of CO₂ extract from T-90 pellets). Using the Deutsche Landwirtschaftliche Geselschaft (DLG) organoleptic evaluation method, the score for “fullness” in the beer brewed with T-90 pellets (beer A) was significantly higher (P < 0.05) than beer brewed with CO₂ hop extract (beer B). The scores for “flavor” and “taste” were higher for beer A than for beer B. The intensity of stale flavor perception was significantly higher (P < 0.05) in beer A than beer B. Beer brewed with spent hops (beer C) was found to have flowery and citrus flavors similar to those perceived in beer A and beer B. Beer C also possessed unique flavors resembling green leaves, wine, and blackcurrants. When beer B and beer C were blended, hop aroma perceptions and harmony of bitterness changed in proportion with the blending ratio. This suggests that polar compounds (hop glycoside, non-isohumulone bitter compounds, and polyphenols, etc.) contained in the spent hop fraction have a strong effect on the flavor and taste of adjunct beer. In a subsequent experiment investigating the influence of the spent hop fraction on adjunct beer, 4 types of adjunct beer were brewed using T-90 pellets (beer D), CO₂ hop extract (beer E), CO₂ extract plus spent hops added at the start of the boil (beer F), and CO₂ extract plus spent hops added at the end of the boil (beer G). Beer E had a markedly lower flavor quality than beer D, and the intensity of flavor, especially citrus flavor, was lower in fresh beer, whereas the intensity of citrus flavor in beers F and G was the same as in beer D. These results suggest that the spent hop fraction increased the flavor quality in adjunct beer. In force-aged beer, beer D displayed a higher stale flavor (mainly cardboard flavor) than beer E. The intensity of cardboard flavor was remarkably lower in beer F and G, and no different from that of beer E. These results indicate the influence of hop fraction on the quality of adjunct beer.

Hitoshi Takemura has worked for Kirin Brewery Company Limited since receiving a master’s degree in life science from Kyoto University in 2002. He worked in the Quality Assurance Department of the Tochigi brewery for three years and then entered the Laboratory for Brewing, where he conducted research on the use of hops in wort boiling. From 2008 to 2010 he worked as a guest researcher in Lehrstuhl fuer Brau- und Getraenke Technologie fuer Technische Universitaet Muenchen. Since August 2010 he has worked in the Brewing Technology Development Center.

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