Modeling the combined effect of high hydrostatic pressure and mild heat on the inactivation kinetics of Listeria monocytogenes Scott A in whole milk

摘要

The survival curves of Listeria monocytogenes Scott A inactivated by high hydrostatic pressure were obtained at four temperatures (22, 40, 45 and 50 deg C) and two pressure levels (400 and 500 MPa) in UHT whole milk. Elevated temperatures substantially promoted the pressure inactivation of L. monocytogenes. A 5-min treatment of 500 MPa at 50 deg C resulted in a more than 8-log-(10) reduction of L. monocytogenes, while at 22 deg C a 35-min treatment was needed to obtain the same level of inactivation. Tailing was observed in all survival curves, indicating that the linear model was not adequate for describing these curves. The log-logistic model consistently produced best fits to all survival curves and the modified Gompertz model the poorest. TheWeibull model produced fits as good as the log-logistic model at the temperature range of 40-50 deg C. The Weibull model provided reasonable predictions of inactivation of L. monocytogenes at temperature levels other than the experimental temperatures; however, the log-logistic model was found to be inferior at predicting inactivation.