Abstract
Aldehydes and ketones play an important role in the flavor stability of beer. We have measured carbonyl compounds such as Strecker aldehydes to investigate the flavor stability of beer. It was found that an unknown gas chromatography(GC)/electron capture detector peak (peak X) of carbonyl compounds after derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine was correlated with sensory evaluations of beer. The peak was determined as ethyl pyruvate (EP) by using GC/mass spectrometry. EP formation was accelerated by decreasing the pH. The formation occurred even at the low temperature (2°C) at which secondary fermentation occurs. EP increased with increasing pyruvate and ethanol during primary fermentation and then decreased with decreasing pyruvate during secondary fermentation. The decrease in EP during secondary fermentation was affected by pyruvate. The amount of pyruvate decrease during secondary fermentation had a positive correlation with the number of yeast cells at the end of primary fermentation. That is, EP is an indicator affected by pH and the number of yeast cells during secondary fermentation, which are important factors for flavor stability. We think EP is an excellent index of flavor stability that can be used to optimize the fermentation conditions, e.g., selection of yeast strains, aeration, and the Drauflassen conditions.
Published Version
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