Reduction of Stale Aldehyde of Beer with Membrane Fraction of Acetic Acid Bacteria

Abstract

  The oxidation of trans-2-nonenal, the main compound causing staleness in beer, with a membrane fraction of acetic acid bacteria was investigated. For use of the fraction, it was necessary to inactivate membrane-bound alcohol dehydrogenase (ADH) first to avoid oxidation of alcohol, while maintaining membrane-bound aldehyde dehydrogenase (ALDH) activity. ADH was completely inactivated by treatment of the membrane fraction at 60°C for 15 min, without any loss of ALDH activity. ALDH activity was not affected by heat treatment even in the presence of 10% alcohol. Results of HPLC showed that a fraction incubated at 60°C for 15 min oxidized 50 ppb trans-2-nonenal added to a commercial beer sample without affecting the alcohol content. Our sensory panel found that the stale odor of trans-2-nonenal disappeared when the membrane fraction was so treated, with the resulting odor better than that of beer with trans-2-nonenal added but not treated with the fraction.