Optimisation of yeast vitality measurement to better predict fermentation performance

Abstract

Brewers are increasingly aware of the importance of yeast health and need appropriate methods to measure its vitality. Many of the current methods are time consuming, expensive or impractical at an industrial scale. Here, the measurement of CO2 production using the ANKOM RF Gas Production Measurement System was optimised. Using response surface methodology, the optimal temperature, yeast biomass and media composition were established. The performance of the method was assessed by measuring the vitality of yeast from laboratory (20 L) and brewery (400-600 hL) fermentations. The drop in pH in early fermentation, diacetyl reduction and fermentation rate were correlated to measurement of yeast vitality. It was shown that the method can be used to assess yeast health and to predict its performance in brewery fermentation. The measurement time was 20 minutes and a minimum vitality of approximately 200 mbar was found to be sufficient for brewery fermentations. The method can be used to optimise yeast propagation processes or to determine the optimal harvesting/cropping time to improve yeast quality, fermentation consistency and beer quality together with reducing cycle time and time in fermenter. © 2020 The Institute of Brewing & Distilling