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The impact of dry hopping on selected physical and chemical attributes of beer - WINNER OF LUDWIG-NARZISS-AWARD 2020
S. Cocuzza, M. Zarnkow, A. Stallforth, F. Peifer and F. Jacob

The scope of this study was to investigate how incrementally increasing dosing rates for dry hoping up to 1500 g/hl with type 90 Cascade pellets affects selected chemical and physical characteristics of beer. To this end, 6 hl of pale ale was brewed on a pilot system. After primary fermentation, this base beer was split in 20 litre NC kegs in order to perform each dry hopping trial in triplicate. From these beers the variations of the following characteristics after dry hopping were investigated: bittering units, alpha acids and iso-alpha acids, humulinones, total polyphenols, flavanoids, iso-xanthohumol and xanthohumol, real extract, alcohol, pH value, foam stability (NIBEM and Steinfurth) and turbidity. In addition, the influence of the plant material from the hops on these selected characteristics was examined. For this purpose, dry hopping trials using 1000 g/hl of spent hop pellets sourced from hop extraction with CO2 were also performed on the same base beer. As a result of our trials, significant effects were observed with regard to the decrease in iso-alpha acids and foam stability, as well as an increase in humulinones, the pH value, real extract and total polyphenols in the instances where type 90 pellets were used for dry hopping. In particular, the decrease in iso-alpha acids appears to be linked to the presence of hop plant material. In contrast to the changes mentioned above, either behaviours of certain compounds remained unchanged or no clear conclusion was able to be drawn concerning the influence of dry hopping on the following: flavanoids, iso-xanthohumol, xanthohumol and alcohol content as well as the turbidity and the bittering units determined analytically.

Descriptors: dry hopping, bitter substances, polyphenols, foam stability, turbidity, pH value, real extract and alcohol content, spent hop pellets

BrewingScience, 72 (May/June 2019), pp. 118-124