MALT RESTRICTIONS ON FERMENTATION

Thursday 6 November 2008

The brewing industry has well-established procedures for determining malt quality but these sometimes do not adequately predict the onset of such problems as incomplete fermentation, premature yeast flocculation (PYF) during fermentation and gushing of the final beer.

It has been suggested that antimicrobial substances which may include, for example, antiyeast compounds present in the malt may be responsible for problematic fermentations but, until now, this has remained speculation.

Scientists at the University of Stellenbosch and SABMiller plc in Sandton, South Africa have developed a method, adapted from microbial assays, to examine the antiyeast activity of malt.

With their procedure, they were able to detect various kinds of antiyeast activity in different malt samples and found that malts associated with PYF and gushing possessed high degrees of antiyeast activity. Both of these faults are associated with fungal infection occurring in barley in the field and it is conjectured that this results in elevated levels of antimicrobial activity in the malt. Food Microbiology 25(7):895-901, 2008 : Optimised quantification of the antiyeast activity of different barley malts towards a lager brewing yeast strain / van Nieropa SNE, Axcell, BC, Cantrell IC, et al

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