Impact of Storage Temperature on Lager Brewing Yeast Viability, Glycogen, Trehalose, and Fatty Acid Content

J. Am. Soc. Brew. Chem. 70(2):123-130, 2012 Maintenance of yeast slurry quality during storage between successive fermentations (serial repitching) is critical for yeast performance during fermentation. An assumption is made in brewing that all strains benefit from storage at 3-4 degrees C. To investigate this assumption, the widely deployed lager yeast strain Saccharomyces pastorianus W34/70 was exposed to differing storage temperatures (4, 10, and 25 degrees C) in anaerobic conditions under beer. No apparent difference in viability (assessed using citrate methylene violet, and oxanol), glycogen and trehalose intracellular levels, and membrane saturation index was observed between yeast slurries stored at 10 and 4 degrees C. Glucose-induced proton efflux was observed to be reduced for yeast stored at 4 degrees C when compared with that observed at 10 degrees C. Although these observations were not made using full production scale and do not consider fermentation profiles of yeast slurries following storage at 4 and 10 degrees C, they do indicate that optimal storage may be achieved at higher temperatures than typically utilized in the brewing industry.