A combined effect of temperature, pH and NaCl concentration on thermal inactivation of Bacillus stearothermophilus ATCC 10149 spores was analysed. After pasteurisation at 80 degrees C for 10 min, the suspension of bacterial spores were sterilised at the temperature from 110 to 121 degrees C in a medium at different pH values (3-7) and various NaCl concentrations (0-6%). It was observed that the sterilisation temperature and pH of the sterilised medium as well as the concentration of sodium chloride, had a significant effect on spores activation and destruction. The activation of dormant bacterial spores in the medium at the parameters applied is possible already at the pasteurisation temperature. (c) 2005 Elsevier Ltd. All rights reserved.