Inactivation Behavior of Heat-Resistant Bacterial Spores by Thermal Treatments Combined with High Hydrostatic Pressure

Abstract

The inactivation behavior of four kinds of bacterial spores by thermal treatments combined with high hydrostatic pressure (HHP) were investigated in a temperature range of 35-120°C and in a pressure range of 0.1-400 MPa. The survival curves of each species of spores became linear at 0.1 MPa, but indicated different time courses by the treatments. The survival curves of B. subtilis and B. stearothermophilus spores became convex downward in the treatments, whereas those of B. coagulans and C. sporogenes spores were linear. Each spores did not die by heating below 100°C at 0.1 MPa. However, the HHP thermal treatments below 100°C quickly killed the bacterial spores except for the B. coagulans. Some of the B. stearothermophilus spores remained alive even at 120°C for 50 min under 400 MPa, whereas the B. stearothermophilus spores surviving at 120°C under 400 MPa started to die when the pressure was released to 0.2 MPa.