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).
