The effect of yeast growth stages on the absorption of polyphenols
Saint-Petersburg State University of Information Technologies, Mechanics and Optics (ITMO University), Faculty of Food Biotechnology and Engineering, Kronversky pr., 49, RU197101 St Petersburg, Russia
*Correspondence: razan.harbah@mail.ru
Abstract:
Colloidal stability of beer is one of the most critical challenges facing the brewing industry. In brewing, stabilization agents are widely used to remove colloids such as proteins and polyphenols. However, the removal efficiency of polyphenols depends on the yeast, which adsorbs these compounds on its surface. The adsorption of polyphenols on the yeast surface is associated with the zeta potential of the cell wall, which correlates with the mannan content in them. The purpose of the study was to investigate the role of yeast strains in adsorption of polyphenols (increasing colloidal stability of beer) and the correlation of this property with the mannan content in the cell wall during the fermentation. Two S. cerevisiae strains were used in this study, and the specific growth rate of yeast, the specific rate of change in the polyphenol content and the mannan content were determined. The results of this study showed that the highest mannan content in yeast was after 9 hours (the end of exponential growth phase). Its content was 10.97% by weight of dry matter in the yeast S. cerevisiae Californian Lager (M54), and 13.69% in the yeast S. cerevisiae Belgian Wit (M21). The desorption of polyphenols was observed during the period from 9 to 24 hours of fermentation, where an increase in the content of polyphenols in the medium was observed. Based on these results, it is necessary to remove the yeast at the end of the exponential growth phase to increase the colloidal stability of the beer.
Key words:
colloidal stability, mannan, polyphenols, S. cerevisiae yeast