Y. MURAOKA (1), T. Kurihara (1), S. Tamura (1), T. Nakamura (1);
(1) Frontier Laboratories of Value Creation, Sapporo Breweries Ltd., Yaizu, Japan
Technical Session 10 - Fermentation
Wednesday, June 17
1:00–2:15 p.m.
Flores 1–2
Many breweries make use of high gravity brewing (HGB) to increase productivity without expanding existing brewing facilities and to save energy. However, HGB has a number of disadvantages. One of the major problems is poor fermentation performance, mainly because of osmotic and ethanol stress on brewing yeast during fermentation. To overcome this problem, various yeast nutrient supplements such as fatty acids, sterols, free amino nitrogen, and so forth, have been used to maintain yeast performance under stressful conditions. Furthermore, the improvement of fermentation has also been attempted through aeration during fermentation. However, this method is time-consuming; it takes about 2 weeks to complete fermentation. In this study, we investigated whether fermentation efficiency can be improved by combining agitation and aeration in a 2.8 L scale fermentation test using 30°Plato wort. This wort was prepared by the addition of corn syrup to all-malt 12°Plato wort. We used bottom-fermenting yeast. Agitation was carried out throughout the fermentation period. Aeration was conducted for 4 days of fermentation. As a result, we concluded that it was possible to produce up to 11% (v/v) ethanol by both agitation and aeration within about 1 week. We measured free and esterified ergosterol content in yeast cells at the end of fermentation. The esterified ergosterol content of yeast with both agitation and aeration was increased compared to when either one of these processes was performed independently, although the amount of free ergosterol was similar among those. Free ergosterol is localized at the plasma membrane, while esterified ergosterol is stored within the lipid granule. It is reported that free ergosterol contributes to the ethanol tolerance of yeast cells. From these results, it was assumed that very high gravity brewing fermentation could be achieved within a shorter period of time, not because free ergosterol improved the ethanol tolerance of yeast, but because yeast grew effectively through the synergy of agitation and aeration.
Yasuhiro Muraoka received an M.S. degree in biological sciences from the Nara Institute of Sciences and Technology. He joined the Hokkaido brewery of Sapporo Breweries Ltd. in 2005 as a brewing engineer. Since 2010, he has been working in the Frontier Laboratories of Value Creation as a lead brewer.
View Presentation
