Hopping Technology in Relation to Beer Bitterness Consistency and Flavor Stability. Barbara Jaskula, Evelien Syryn, Koen Goiris, Gert De Rouck, Filip Van Opstaele, Jessika De Clippeleer, Guido Aerts, and Luc De Cooman (1), Technical University KaHo St.-Lieven, Laboratory of Enzyme and Brewing Technology, Ghent, Belgium. (1) Corresponding author. E-mail: <luc.decooman@kahosl.be>; Phone: +32-(0)9-265 86 13; Fax: +32-(0)9-225 62 69. J. Am. Soc. Brew. Chem. 65(1):38-46, 2007.

The fate of alpha-acids, iso-alpha-acids, and their chemically modified variants was monitored in pilot brews as a function of hopping regime and beer aging. HPLC analysis indicates that alpha-acids, iso-alpha-acids, and dihydroiso-alpha-acids in beer are not stable during forced aging. This is reflected further in the sensory performance of these beers. Beer exclusively bittered with tetrahydroiso-alpha-acids was completely stable, in terms of hop components, under the experimental conditions employed. In addition, overall flavor stability was significantly improved. These results provide further evidence that hop-derived bitter acids, including the light-stable dihydroiso-alpha-acids, could play an important role in beer flavor deterioration during storage. Keywords: alpha-Acids, Flavor stability, Hop products, Iso-alpha-acids, Reduced iso-alpha-acids, Utilization