P-12
Impact of esterase activity in cold-filtered beer. An extracellular yeast esterase found in unpasteurized beer hydrolyzes long
chain esters such as ethyl hexanoate and ethyl octanoate. The enzyme is
competitively inhibited by the presence of octanoic acid. Esterase activity
reaches a maximum at day 2-3 of fermentation, declines, and then returns to the
maximum at EOF as beer temperature decreases. Pasteurization destroys the
activity, but esterase remains active in cold-filtered beer. Lower levels of
total esters and higher levels of total fatty acids were found in cold-filtered
beer stored at 30 C. A correlation was observed between ethyl hexanoate and
hexanoic acid in the stored cold-filtered beer. Octyl acetate, which
significantly decreased in cold-filtered beer during storage at 30 C, was a good
esterase activity indicator. The impact of esterase activity on sensory
evaluation is minimal as the changes in levels of esters and acids were
individually below the level of sensory detection.
Petr Vesely is pursuing Ph.D. studies at the Institute of Chemical
Technology in Prague, Czech Republic. His Ph.D. research topic is "Factors
influencing beer aging". In 2000, he performed research at the Institute
Meurice, Brussels, Belgium, with a European Union scholarship, Erasmus Exchange
Program. In 2001, he completed an internship at the Miller Brewing Company. Petr
has also been a brewer at the Hideji Brewery, Nobeoka City, Miyazaki prefecture,
Japan.
PETR VESELY, Antonia Volgyi, Lance T. Lusk, Alfonso Navarro, John Seabrooks, and
David Ryder. Miller Brewing Company, Milwaukee, WI.