Modeling high pressure inactivation of Escherichia coli and Listeria innocua in whole milk

The survival curves of Escherichia coli and Listeria innocua inactivated by high hydrostatic pressure (HHP) were obtained at room temperature (similar to 22 degrees C) and at five pressure levels (400, 450, 500, 550 and 600 MPa) in whole milk. These curves were described by the Weibull model and parameters of this model were reduced from two to one with slight loss of goodness-of-fit. The logarithm of the time constant parameter (delta) of the reduced Weibull model was described with respect to high pressure (P). This approach can be used to define a z(p) value analogous to the modeling of the classical D value (increase in pressure that results in one log unit decrease of delta values). The development of accurate survival models under high pressure, as presented here, can be very beneficial to food industry for designing, evaluating and optimizing HHP processes as a new preservation technology.