YEAST AUTOLYSIS AND THE BIOLOGICAL STABILITY OF BEERS

Abstract

It is known that (a) Lactobacillus spp. differ strain-specifically in their nutritional requirements; (b) wort is a good medium for the growth of most species of Lactobacillus whereas beer is a relatively poor medium; (c) the products of yeast-protein autolysis do not in the main show strain-specific differences of composition, either in the nature of the amino acids present or in their relative concentrations; (d) the amino acids found in yeast autolysate cover the whole range known to be essential for Lactobacillus growth. An attempt has accordingly been made to determine whether the rates of autolysis in different yeasts differ strain-specifically to such an extent that the beers obtained differ significantly as growth media for lactobacilli. In general, it has been found that these rates of autolysis do not control the biological stability in a consistent way. There is no correlation persisting throughout the experimental series between rate of autolysis and growth-supporting properties of the beers, though such correlation is observed in extreme cases.