Measurement of Brewing Yeast Flocculation

Abstract

For the production brewer, predicting fermentation performance may also involve the determination of flocculation capacity of a given yeast slurry. Several methods have been reported and a few, most notably the Helm's Test, have been adopted as recommended methods of analysis by various brewing societies. It has been suggested that the Helm's test could be further developed to include additional extrinsic factors known to influence flocculation. Accordingly, the flocculation of FLO1 and New FLO ale and lager brewing yeast strains was quantified using modified versions of the Helm's test with a view to developing a rapid, reproducible method of analysis. An increase in the growth incubation period from 48 to 72 hr is recommended to ensure that cell proliferation has ceased and lectin activation and maturation has occurred. To differentiate between weakly and non-flocculent cell populations, it was observed that an extension in sedimentation period during the flocculation assessment was required. For cells grown in standard laboratory media, the temperature at which the assay was conducted did not affect flocculation potential, and the utilization of an EDTA or sugar-based prewash to deflocculate populations prior to examination did not affect the percentage of flocculation observed. However, the inclusion of ethanol in the buffers used to assess flocculation is recommended, though its impact was largely strain dependent.