H. NAKAMURA (1), T. Maruhashi (1), Y. Hida (1); (1) Suntory Beer Limited, Osaka, Japan
Yeast, Fermentation, and Microbiology I
Friday, October 9
Hydrogen sulfide (H2S) gives beer an unpleasant off-flavor like that of rotten eggs, so it is important to keep the H2S content in the final beer product well below the sensory threshold. H2S behavior during fermentation has been investigated, and it is known that the behavior is related to yeast cell growth and the process of fermentation. It is released from yeast cells during the cell maturation period and assimilated during the budding period. The decrease in the H2S content of beer during late-stage fermentation is attributed to the purging effect of carbon dioxide (CO2) and assimilation by yeast. In 2013, we reported at the MBAA Annual Conference that H2S content was decreased again in late-stage fermentation according to the balance between its production, its assimilation, and the CO2 purging effect when the malt ratio of wort is low. In this study, we examined H2S content during fermentation using all malt wort and observed another behavior in this case. H2S content during fermentation increased at a certain time in late-stage fermentation. Since such phenomenon was not well known, we investigated the relationship between the H2S content and the consumption of sugar during the fermentation process for further understanding of this phenomenon. As a result, sugar consumption by yeast almost stopped and glycogen content in yeast cells decreased at the same time in late-stage fermentation. So it was suggested that the end of sugar consumption by yeast leads to the increase of H2S in late-stage fermentation.
Hiroshi Nakamura graduated with an M.S. degree from Kyoto University in 2008. After joining Suntory, he worked for 2 years in the Beer Development Department. He then went to Suntory (China) Holding Co., Limited, and worked there for 2 years. Hiroshi currently works in the Beer Development Department of Suntory Beer Limited.