Abstract:

In order to explore the thermal effect of microwave sterilization, lethal effects of microwave and water-bath heating treatments on Bacillus subtilis var. niger spores were compared at various heating temperatures and time. After the activation of Bacillus subtilis var. niger spores, the spore suspension at the concentration of 104 CFU/mL was prepared. Microwave and waterbath heating treatments were used for the sterilization of spores to evaluate the lethal rate. Results indicated that the lethal rate at 92 ℃ was higher than that at 85 ℃ for both microwave and water-bath heating treatments. At the identical condition of heating temperature (85 ℃) and time, the lethal effect of microwave treatment was much better than that of water-bath heating treatment, which was due to an obvious non-thermal effect. However, no obvious difference in lethal rates of microwave and water-bath heating treatments at 92 ℃ for 20 min was exhibited.

Key words: microwave, sterilization, thermal effect, non-thermal effect, Bacillus subtilis var. niger spore