Thermal Death Characteristics of Spores of Clostridium botulinum 62A and Bacillus stearothermophilus Subjected to Non-isothermal Heat Treatment

Abstract

The differences of thermal death characteristics of spores of C. botulinum 62A and B. stearothermophilus subjected to isothermal and non-isothermal treatments were investigated. In the course of non-isothermal treatment (temperature rise at a constant rate of 1 or 4°C/min from ca. 50°C), the survival number of B. stearothermophilus spores decreased almost exactly as theoretically predicted based upon the thermal death time (TDT) parametric values which had been determined preliminarily by conventional isothermal treatment. The survival number of C. botulinum 62A spores heated at a temperature increase rate of 1°C/min decreased along the maximum limit of the predicted thermal reduction curve. The survival number of the same spores lot heated at the rate of 4°C/min decreased in a manner scattered between the minimum and the maximum limits of the predicted thermal reduction curves.No significant differences in TDT parametric values was observed between isothermal and non-isothermal treatments for the spores examined.