Optimized conditions for pre-treatment of hops in the brewhouse to maximize utilization rate without a decrease in beer quality

Technical Session 11: Brewhouse Operations Session
Sebastian Kappler, Technische Universität München, Institute for brewing and beverage technology
Co-author(s): Martin Zarnkow and Thomas Becker, Technische Universität München, Institute for Brewing and Beverage Technology, Germany

ABSTRACT: Iso-alpha-acids are the main contributors to bitterness perception in beer. In the brewing process, however, only about 30% of the alpha-acids present in hops are isomerized and transferred into the finished beer. To reduce costs for hopping of beer by an increase in utilization rate, several solutions have been suggested over the past few years. Mostly either the use of pre-isomerized hop products or a pre-treatment of hops prior to dosage has been described. Formerly presented results showed a highly significant decrease in bitterness quality and aging stability with the increase in utilization rate achieved by isomerization of hops prior to dosage. Probably due to a high amount of degradation products of alpha-, beta-, and iso-alpha-acids, a harsh bitterness was created. Also, aging stability was reduced due to polymerization reactions of hop and malt polyphenols during thermal treatment of hop pellets together with common lauter wort. It was obvious that further studies to increase the quality of the resulting beer while using pre-isomerization technology was necessary. In this work the influence of various technologies and varying parameters for treatment of hop products was evaluated. Pilot-scale trials, as well as industrial-scale trials, were done to evaluate the influence of various technologies on sensorial and analytical attributes, as well as behavior during aging of beer. Particular attention was paid to the bitterness profiles of fresh and forced-aged beers. All brews were analyzed in comparison to common brewed beers. This paper presents solutions to increase utilization rate while maintaining the quality of bitterness as well as aging stability. Pre-treatment of hops can be enhanced by optimizing the time and temperature of treatment while reactions are minimized, for example, by optimizing the composition of the medium. The influence of the use of different catalysts and lauter fractions, as well as variations in pH value, is shown. Finally, the influence of variations in point of dosage to the boiling wort is exposed. Suitable approaches toward an improved yield of bitter acids together with an acceptable bitter quality are shown!

Sebastian Kappler received a Dipl.-Ing. degree in brewing and beverage technology from Technische Universität München in 2008. He began his employment with the Augustiner-Wagner Brewery in Munich as an apprentice to a brewer and maltster in 2000. After becoming an assistant he started his studies on brewing science at the Technische Universität München. Since May 2008 he has been working as a scientific employee at the Institute for Brewing and Beverage Technology in Weihenstephan. The topic for his doctoral thesis is the evaluation of the factors affecting the yield of isohumulones during preparation of wort.