Bottle conditioning is an additional fermentation process where yeast and fermentable extract are added to the beer for natural carbonation. Importantly, the yeast must be able to withstand various environmental stresses in order to conduct sufficient fermentation in the bottle. It is also desirable for the yeast to survive an extended period of time, as a decline in viability will lead to undesirable alterations in the final product.
We conducted a multifaceted investigation into the effects of bottle conditioning on beer using six different yeast strains from the brewing, wine making, and distilling industries. The ale and lager strains resulted in a beer possessing typical characteristics of a pale ale-style beer, whereas the sparkling wine and distilling yeast strains resulted in uncharacteristic aromas. We also observed among the strains different survivorship characteristics during bottle conditioning over a 120 day period. A proteomic analysis was conducted to investigate protein abundance changes that might reveal the underlying biological processes associated with better survivorship properties during secondary fermentation. We found increased protein abundances associated with oxidoreductase activity and mitochondrial ribosomes in the yeast strain with superior survival capabilities, whereas proteins associated with cell wall modulation were increased in the strain with the poorest survival characteristics. These results provide an insight into the biological processes that allow yeast to respond to cellular stress during bottle conditioning, as well as the importance of yeast selection for bottle conditioning to promote desirable beer properties.