EFFECT OF GROWTH TEMPERATURE AND GLUCOSE ON THERMAL INJURY OF SACCHAROMYCES CARLSBERGENSIS

Abstract

Fermentation temperature markedly affects the flavour of lager beers. The influence of growth temperature on the thermal stability of a strain of S. carisbergensis was examined in a model fermentation system. At 40° C in the presence of glucose there was substantial leakage of yeast cell contents, the extent of which was a function of growth temperature. Increased incubation time at 40° C prior to glucose addition increased the glucose-induced leakage. Similar results were achieved with cells preincubated at 40° C and then added to glucose solution at 30° C. Without heat treatment or without glucose, growth temperature had little effect on leakage of cell contents. Ca++ protected against glucose-induced leakage, but only in the initial stages. Leakage was independent of the osmotic pressure of the medium, and was caused only by fermentable sugars, and cells so treated exhibited characteristics of a ruptured cytoplasmic membrane, ATPase activity and inability to retain accumulated sorbose at 0° C.