| Abstract: | The persistence of low levels of contamination by non-brewing Saccharomyces through several batch fermentations establishes the immuno-fluorescent method as a very sensitive procedure for estimating the microbiological purity of pitching yeasts. Trade return figures for draught beers show that in this brewery the principal cause for high rejection rates has, on several occasions, been contamination of pitching yeasts with “wild” Saccharomyces. The recommendation is made that pitching yeasts should be discarded when the level of infection achieves 100 cells of wild Saccharomyces per million cells of brewing yeast. |
