Thermal inactivation kinetics of sugar-tolerant yeasts

Abstract

The thermal inactivation kinetics of two sugar-tolerant yeast strains — Zygosaccharomyces rouxii CBS 732 and Zygosaccharomyces rouxii T 15-and the non-tolerant strain Saccharomyces cerevisiae CBS 1171 has been determined in different sucrose concentrations up to 1.96 mol · l−1. The influence of water activity (aw) in terms of different sucrose concentrations in the heating menstrua was studied and the thermal inactivation reactions were characterized by apparent activation energies (E). A linear relationship between the logarithm of activation energy and the sucrose concentration in the heating menstruum was established. Increasing sucrose concentration in the heating medium was followed by an increase in heat resistance of the test microorganisms. In spite of differences, the activation energies were of the same order, suggesting that similar, highly organized functioning biopolymers must be responsible for the death of heat treated vegetative yeast cells.