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2017 Master Brewers Conference
47. What are "auxiliary bitter compounds" in hops and how do they affect the quality of bitterness in beer?

Andreas Gahr, Hopfenveredlung St. Johann GmbH, Train - St. Johann, Germany

Coauthor(s): Florian Schüll, HVG Hopfenverwertungsgenossenschaft e.G., Wolnzach, Germany; Adrian Forster, HVG Hopfenverwertungsgenossenschaft e.G., Wolnzach, Germany

Friday, October 13
3:45–5:00 p.m.
Imperial Salon B

The term "auxiliary bitter compounds in hops" refers to all bitter compounds in the hop resin that are transferred to the beer and are not iso-α-acids. This includes all such components found in fresh hops and excludes those formed through oxidative aging reactions. There are numerous auxiliary bitter compounds found in hops that are either present in a directly soluble form in hops or are formed from α-acids and β-acids during the wort boiling process. The majority of these substances are considered desirable from a sensory perspective. They mask a harshness and lingering character of the bitterness and make a positive contribution to the quality and harmony of the bitterness in beer. The ratio of the non-specific EBC bittering units (spectrophotometric method) to the specific iso-α-acids (HPLC method) serves as an indicator for the amount of auxiliary bitter compounds in beer. This ratio is equal to 1 in beers brewed with only one hop addition of high-alpha hops at the beginning of the boil, in which case the bittering units are equivalent to the iso-α-acid content. By contrast, beers brewed with a complex hopping regimen, e.g., with several additions of aroma hops, exhibit significantly higher levels of bittering units than iso-α-acids. Here, the values for IBU to iso-α-acids have been measured as high as 2. In this situation, the iso-α-acids are present in comparable quantities to the non-iso-alpha bittering units. Thus, auxiliary bitter compounds make up a sizable portion of the bittering units. The results from brewing trials show that the bitterness of beers with higher ratios of IBU to iso-α-acids is less harsh and lingering, while the overall impression is more balanced and pleasant. Adding larger amounts of aroma hops over several additions not only influences the aroma of the beer but also serves to round out the bitterness of the beer.

Andreas Gahr was trained on the job of a brewer and maltster at the Augustiner Brewery, Munich, Germany. He received a brewmaster degree from the Technical University Munich-Weihenstephan in 1994 and worked for another four years at the university for the Chair of Brewing Technology I. Since 1998 Andreas has been the head of the Research Brewery St. Johann, which belongs to the hop processing company Hopfenveredlung St. Johann GmbH and deals with all kinds of hop-related brewing trials and product development as well as technological and raw material trials for suppliers and the whole brewing industry. He is an experienced taster and judges for a number of international beer and brewing competitions. Together with others, he wrote several publications and a book on hops and received together with other authors the MBAA Inge Russel Best Paper Award in 2010 and the Ludwig Narziß Award for Brewing Science in 2015.

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