Katsuyuki Seki (1), Taku Irie (1), Itsuo Nishitani (1), Takeshi Sasamoto (1), Kazuhiko Uemura (1); (1) Asahi Breweries, Ltd., Tokyo, Japan

Yeast, Fermentation, and Microbiology

The fermentation process in brewing contains a lot of factors that regulate the flavor of beer. In particular, it is important to control temperature precisely in the fermentation process to ensure stable beer quality. Fermentation is generally regulated through temperature control during the various yeast growth phases. We measure sugar attenuation and the number of yeast daily in beer to obtain information about appropriate time to control fermentation temperature. As a result of this, the flavor substances in yeast products are regulated in beer. In an effort to improve this technique, we developed a method to theoretically predict the changing point in the yeast growth phases by fitting the attenuation data during fermentation to a sigmoid curve (Irie, 2015). In consequence, we found out the inflection points associated with flavor control and applied it to decrease undesirable flavor in industrial scale fermentation. On the other hand, in this report, we developed the method to control fermentation temperature precisely in cylindroconical tanks. The temperature inside the tanks have usually been monitored with a single thermometer. However, distribution of temperature in the tanks was found to be nonuniform when we measured it at multiple locations. Additionally, the distribution of temperatures was confirmed to differ among fermentation tanks. To minimize this difference among tanks as much as possible, we established a way to predict the distribution of temperature without measurement. In particular, we found an indicator that predicted it in tanks from coolant flow rates and the period of cooling during fermentation. And, we adjusted the valve position of coolant for appropriate flow rates in cylindroconical tanks using this indicator. Thereby, the distribution of temperature among the tanks could be made uniform. This indicator allows temperature control in fermentation to be regulated precisely so that it contributes to ensuring the stable quality of beer. By following the approaches described above, we aim to reduce differences in fermentation conditions among the tanks, further improving beer flavor.

Katsuyuki Seki graduated from the Faculty of Agriculture, Tokyo University of Agriculture and Technology, Japan. After that, he received an M.S. degree from the Graduate School of Agricultural and Life Sciences, University of Tokyo, Japan. He began employment with Asahi Breweries, Ltd. in April 2006 as a technical staff in the brewing section. After he had worked at several breweries, he was transferred to the production technology center in September 2014. He has been involved in researching factors to control fermentation in practical brewing.