ORIGINAL PAPER Compression Heating and Temperature Control for High-Pressure Destruction of Bacterial Spores: An Experimental Method for Kinetics Evaluation Yanwen Shao & Songming Zhu & Hosahalli Ramaswamy & Michèle Marcotte Received: 4 November 2007 / Accepted: 17 January 2008 / Published online: 10 February 2008 # Springer Science + Business Media, LLC 2008 Abstract 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 temper- atures for the test sample and pressure medium were generated as a quadratic function of pressure and temper- ature. 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. Keywords High pressure . Compression heating . Temperature control . Kinetics . Microbial destruction . Adiabatic compression Introduction High pressure (HP) is a novel method of food processing to achieve microbial inactivation or to alter the food attributes to get desired qualities. The unique physical and sensory properties of HP-processed foods offer many potential opportunities for food processing. HP processing has been reported to be effective in reducing or eliminating microbial pathogens for refrigerated and high-acid foods (Patterson 2005). However, bacterial spores are highly resistant to pressure destruction (Sale et al. 1970; Mills et al. 1998). HP sterilization of low-acid foods is more difficult and complex but may be achieved by combining HP with elevated temperatures (Furukawa et al. 2003; Reddy et al. 2006; Scurrah et al. 2006). During an HP treatment, pressurization has two physical consequences that affect the microbial spore destruction kinetics: (1) pressure increase and (2) adiabatic compression heating resulting in a temperature increase, both having potential to increase the spore kill rate. The HP treatment can thus start with a relatively lower initial temperature and use compression heating for a quick temperature increase (3–9 °C/100 MPa, depending on the product temperature Food Bioprocess Technol (2010) 3:71–78 DOI 10.1007/s11947-008-0057-y Y. Shao : S. Zhu : H. Ramaswamy (*) : M. Marcotte Food Science Department, Macdonald Campus, McGill University, 21111 Lakeshore, Ste Anne de Bellevue, Quebec H9X 3V9, Canada e-mail: hosahalli.ramaswamy@mcgill.ca S. Zhu : M. Marcotte Food Research and Development Centre, Agriculture and Agri-Food Canada, 3600 Casavant Blvd West, St. Hyacinthe, Quebec J2S 8E3, Canada