Compression heating and temperature control for high-pressure destruction of bacterial spores: An experimental method for kinetics evaluation

High-pressure (HP) processing is considered as an alternative technique for thermal sterilization of high quality foods. Adiabatic compression during pressurization allows for quick increase in temperature of food products, which is reversed when the pressure is released, thereby providing rapid heating and cooling conditions and hence short process times. However, during the pressure holding time, the product experiences a temperature drop as a result of heat loss to the vessel. The temperature variation during the process and the synergistic effect of temperature and pressure make it difficult to get the required accurate data on microbial spore destruction kinetics. In this study, a polyoxymethylene (POM)-insulated chamber was evaluated for temperature control in the test sample during pressure treatment. Temperature variations in the HP system were measured in milk test samples inside the POM insulator and pressure medium in the HP vessel under various conditions of pressures (500-900 MPa) and initial temperatures (20-80 °C). Results demonstrated that the POM chamber had good thermal-insulation characteristics under pressure and was able to maintain stable operating conditions for microbial spore destruction kinetics. Based on the measured adiabatic temperature change, the required initial temperatures for the test sample and pressure medium were generated as a quadratic function of pressure and temperature. The setup was then verified for pressure inactivation of Clostridium sporogenes (PA 3679) spores in ultra-heat-treated milk. The better temperature stability of test samples during treatment provided a means to gather accurate data on HP destruction kinetics of the microbial spores. © Springer Science + Business Media, LLC 2008.