MODELING THE INACTIVATION OF LISTERIA MONOCYTOGENES BY COMBINED HIGH PRESSURE AND TEMPERATURE USING WEIBULL MODEL

摘要

Inactivation curves of Listeria monocytogenes by high pressure were obtained atnthree pressure levels (400, 500 and 600 MPa) and three temperature levels (27, 43nand 60C) in ultra-high temperature (UHT) whole milk. The milk samples afterntreatment were plated on both nonselective and selective media to determine thenlog reduction value and to obtain the inactivation curve. The inactivation curvesnwere fitted to the widely used two-parameter Weibull model with parameters an(characteristic time) and b (shape factor) and a reduced one-parameter Weibullnmodel where the a value with the correct physical interpretation was predetermined.nThe log reduction value at the characteristic time from the regressed twoparameterWeibullnmodel and the experimental data must both be 0.434; however,nin the literature, there is evidence that the regressed model and the experimentalnvalues do not match always. Accordingly, this study focuses on the two-parameternand one-parameterWeibull models to bring out this inconsistency. Although therenwas loss in goodness of fit by adapting the one-parameter model, yet the modelnrepresented the correct physical interpretation of parameter a. Development ofnsuch mathematically consistent models may help industry to design, develop andnoptimize safe processing conditions that are based on reliable model parameters.