Kinetic study of Bacillus cereus spore inactivation by high pressure high temperature treatment

• Kinetics of B. cereus spore inactivation by HT and HPHT at 0.1 and 600 MPa, 60–100 °C
• HPHT inactivation is considerably faster than HT at the same temperature.
• HPHT inactivation kinetics is non-first-order, with a rapid and a slow phase.
• 6-D reduction after about 5 min at 600 MPa at 100 °C or 12 min at 90 °C

The purpose of this work was to compare inactivation of spores from the heat resistant Bacillus cereus strain F4430/73 by high pressure treatment at elevated temperature (HPHT) versus thermal treatment (HT). Spore suspensions were treated at 0.1 and 600 MPa at 60–100 °C for different times. HT inactivation could be described by a first-order kinetic model, while HPHT inactivation showed a fast followed by a slow phase. Significant spore inactivation occurred during pressure come-up and equilibration time (2.0 to 4.1 log10, from 70 to 100 °C). HPHT inactivation proceeded considerably faster than HT inactivation, even in the slow phase which also followed first-order kinetics (e.g. D100 °C(600 MPa) = 1.7 min, D100 °C = 3.4 min). The D values at 0.1 and 600 MPa also showed a distinct temperature dependency, with z values of 10.6 and 21.2 °C, respectively. The data indicate a strong synergistic effect of HP and HT on inactivation of B. cereus spores.Industrial relevanceHPHT processing is an emerging technology for the production of shelf-stable and safe foods with a higher quality than conventional thermal appertization. Quantitative data on the inactivation of bacterial pathogens, in particular from sporeformers, is essential to demonstrate that the process is indeed safe and efficient, and to develop a methodological framework for process calculation and validation. The current work is one of the first to provide such data on the inactivation of B. cereus, which is among the most important sporeformers in terms of food spoilage and safety.