TEMPERATURE-DEPENDENCE OF THERMAL INACTIVATION RATE CONSTANTS OF BACTERIAL-SPORES IN A GLASSY STATE

Differential scanning calorimetry data obtained from corn embryos is consistent with the hypothesis of their glassy state. This work extends that hypothesis to explain the speculation about the high heat resistance of bacterial spores. By considering the protoplast to be in a glassy solid-state, it can be assumed that the configurational rearrangements of the key life dependent polymer chain backbones (DNA, etc.) are extremely slow, thereby ceasing thermal motions. It is assumed that at the glass transition temperature, the spore protoplast undergoes a discontinuity in the thermal expansion coefficient, and above this critical temperature, the rate of thermal inactivation of spores is free volume dependent and can be described adequately by the William, Landel and Ferry (WLF) equation. Glass transition temperatures for Bacillus stearothermophilus and Clostridium botulinum spores, obtained by fitting the inactivation rate data to the WLF equation, indicate a decrease in the inactivation rates with increasing glass-transition temperatures.