Cornell University Biological and Environmental Engineering

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Uncertainty in Thermal Process Calculations Due to Variability in First Order and Weibull Kinetic Parameters

Introduction

Alternatives to first-order model of death kinetics of microorganisms have been proposed as improvements in the calculation of lethality for a thermal process. Although such models can potentially improve predictions for many situations, this article tries to answer the question whether the added complexities of these models are worthwhile investment once we include the effect of uncertainties in various microbiological and process parameters.

Method

A simple code is written in MATLAB to solve for the log-reduction in bacterial population and Monte-Carlo simulations done with 1000 repetitions for each prescribed temperature profiles. For canning process, heat conduction equation is solved in Comsol Multiphysics and results read in Matlab where log-reduction is solved. The procedure followed in Monte Carlo simulations is explained in Fig.1. A uniform distribution of D & z for first order kinetics and b & n for Weibull kinetics is taken. The mean of this distribution is the value from literature. The range of the distribution depends on the CV selected.