HEAT PROCESSING OF SPENT BREWER'S YEAST

Abstract

ABSTRACTMoist heat treatments of brewer's yeast at cell populations of approximately 106/ml resulted in biphasic but otherwise typical survival curves. Brewer's yeast was shown to suffer either thermal injury or death over the tested temperature range of 47–53°C. Recovery from thermal injury was possible in liquid media at 20–30°C. Death kinetics were predictable and reproducible. At cell concentrations found in industrial yeast slurries ∼5 × 105/ml), pasteurization of spent yeast could not be planned by assuming normal first order kinetics, as dying cells released materials which altered the thermo‐resistance of survivors. Under simulated yeast slurry conditions however, with protective cell supernatant (menstruum) obtained after vigorous heating of slurried yeast, a phantom thermal death time curve was obtained which could be used to accurately predict yeast kill (decimal reduction time) at slurry concentrations and at any temperature.