Presenter: Koji Nakazawa, Asahi Breweries, Ltd., Moriya, Japan. Coauthor(s): Yuichi Nakamura, Asahi Breweries, Ltd., Osaka, Japan.
Yeast activity has been investigated on the basis of the proportion of viable cells and the physiological status and function of viable cells, and many variables have been devised to evaluate yeast viability and vitality. Among these methods is the oxygen consumption method, which makes it possible to keep track of specific yeast vitality to some degree by measuring the oxygen consumption rate at a set temperature over a fixed period of time. However, it has been considered difficult to keep exact track of slight differences in yeast vitality in the brewing environment. We investigated whether it was possible to use the oxygen consumption rate in our breweries to predict yeast vitality and the progress of fermentation, with the goal of achieving stable management of the fermentation. As a result, oxygen consumption rate was different depending on the physical conditions of yeast and handling conditions, and the rate decreased when the yeast was stored for a few days. The rate was controllable by changing temperature conditions in the wort cooling process. In the 500-kL industrial-scale study, it was confirmed that by increasing wort temperature, the yeast stored for a long time achieved an oxygen consumption rate equivalent to the yeast collected on the test day, and the fermentation performed well. These findings suggest that the rate of oxygen uptake can be used to evaluate yeast vitality and manage fermentation. It is important to control oxygen uptake conditions according to the behavior of yeast.
Koji Nakazawa received an M.S. degree in biotechnology and macromolecular chemistry from Hokkaido University, Japan. He began employment with Asahi Breweries, Ltd. in April 2005. After working as a brewer in Suita brewery (Osaka), he was transferred to the brewing section of Hokkaido brewery (Hokkaido). He has been working in the Production Technology Center since 2009.
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