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O-42. Factors influencing the losses of bitter substances and possibilities to increase the yield during brewing

Presenter: Frank-Jürgen Methner, Technische Universität Berlin, Berlin, Germany
Coauthors: Thomas Kunz and Mario Marinoff, Technische Universität Berlin, Berlin, Germany

Bitter substance utilization during conventional beer production is quite low and still a major problem for the brewing industry. Brewing trials were conducted to evaluate the effect of pH and iron on bitter substance yield. In addition to fermentation trials, hopped and unhopped worts with and without iron addition were adjusted to different pH values. Bitter substance yield was significantly influenced by both pH and iron concentration. Acidifying the system yielded reduced bitter units, hop acid, and iron concentration. Regardless of the initial pH, bringing the pH to alkaline conditions again caused the highest results. Iron content in unhopped wort was unaffected by pH adjustment. The results suggest that reversible, pH-dependent hop-acid-iron complexes are formed and are mainly responsible for the loss of bitter substances during fermentation. Additional trials are presented that demonstrate that the outcomes of this research can be used to recover hop acids from hot trub.

Frank-Jürgen Methner conducted studies in brewing science at Berlin Institute of Technology (TU) from 1975 to 1981. After the studies, he began working as an operating supervisor at the Schlösser Brauerei, Düsseldorf. From 1982 to 1986, he was a scientific assistant with teaching duties at TU Berlin. Research projects and Ph.D. thesis, “Aroma Formation of Berliner Weissbier with Special Focus on Acids and Esters,” were further tasks. For 18 years, starting in 1987, he held a leading position as a director at the Bitburger Brauerei, Bitburg, Germany, with responsibilities in fields such as research and technology, as well as quality assurance. Beginning with the winter semester 2004/2005 he took over the Chair of Brewing Science within the Department of Biotechnology at Berlin Institute of Technology (TU Berlin).