Mathematical modeling of Escherichia coli inactivation under high-pressure carbon dioxide.

Inactivation curves of Escherichia coli under high carbon dioxide pressures (2.5, 5.1, 7.6 and 10.1 MPa) at different temperatures (20, 30, 40 and 45 degrees C) were analyzed using the modified Gompertz model. The phase disappearance (time for complete inactivation of all cells, lambda) and the inactivation rate (mu) of E. coli were inversely related. Inactivation rates (mu) of E. coli were higher at 45 degrees C under 10.1 MPa CO2 pressure than at 25, 30 and 40 degrees C under 2.5, 5.1 and 7.6 MPa CO2 pressure. Increased pressure and temperature had significant effects on the survival of E. coli. The temperature dependence of the inactivation rate constant was analyzed based on the Arrhenius, linear and square-root models. The temperature sensitivity (high E(mu)) determined based on the Arrhenius model was higher at high temperatures. E(mu) (activation energy) value was -186.56 Kjoule/mol at 10.1 Mpa, and -137.24, -167.25 and -183.80 Kjoule/mol at 2.5, 5.1 and 7.6 MPa, respectively. Results of this study enable the prediction of microbial inactivation exposed to different CO2 pressures and temperatures.