Application of a Newly Developed Method for Estimating the Premature Yeast Flocculation Potential of Malt Samples

Abstract

Premature yeast flocculation (PYF) is a serious problem in the brewing industry. Yeast flocculate prematurely during yeast fermentation while high sugar concentrations remain and lead to a marked reduction in the number of yeast cells, all of which impact beer quality. It is very important for brewers to know the PYF potential of malt. Consequently, a simple two-day fermentation method to estimate the PYF potential of malts was developed on a 50-mL scale in which the cropping yeast of breweries and propagated lager yeast cultures can be used. The method is useful for purchasing the malt batches and estimating the effect of blending malts at the breweries. This newly developed method could be a good tool for research on PYF, and we have concluded the following: 1) long-term storage of malt had no effect on decreasing the PYF potential; 2) washing whole malt was effective in decreasing the PYF potential; 3) all the ale yeast examined was not clearly influenced by PYF-positive malt; and 4) all the lager yeast examined was sensitive to PYF malt even if it was nonflocculent.