In this study, the effects of infrared radiation (IR) on inactivation and injury of two kinds of bacterial spores (B. pumilus, B. subtilis) were investigated. Inactivation and injury of these spores suspended in sterile distilled water by IR were compared with those by convection heating (HC). The temperature of spore suspension irradiated by infrared ray was a close profile to that heated by convection within the range from room temperature to ca. 97°C. The inactivation of bacterial spores by IR was more intensive than that by HC. It took about 8 and 12 min of IR treatment to inactivate 99% of B. subtilis and B. pumilus spores, respectively. These bacterial spores were injured by IR more extensively than by HC in the initial stage of 4 min the same bulk temperature of suspension despite. When bacterial spores air-dried on a stainless petri dish were directly irradiated (direct irradiation) by IR without water, direct irradiation by IR could suppress the bacterial spores in a short time comparing with dry heat sterilization by HC. And, the method by IR could inactivate 90% of both kinds of spores having different heat tolerance for almost same periods (1.0 kW: 1 min, 0.5 kW: 2 min), however, B. pumilus spores were more liable to be injured than B. subtilis spores by direct irradiation.
All Science Journal Classification (ASJC) codes
- Food Science