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

Abstract

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 of whether the added complexities of these models are a worthwhile investment once we include the effect of uncertainties in various microbiological and process parameters. Monte Carlo technique is used to include variability in kinetic parameters in lethality calculation for a number of heating processes, for both first-order and Weibull kinetics models. It is shown that uncertainties represented by coefficient of variation in kinetic parameters lead to a wide range of final log-reduction prediction. With the same percent variability in kinetic parameters, uncertainty in the final log reduction for Weibull kinetics was smaller or equal to that for first-order kinetics. Due to the large effect of variability in the input parameters on the final log reduction, the effort to move toward more accurate kinetic models needs to be weighed against inclusion of variability.

Thermal inactivation of Listeria monocytogenes in ground beef under isothermal and dynamic temperature conditions

“…Apparently, the coefficient K affects the rate of bacterial inactivation, and a determines the shape of an inactivation curve under isothermal conditions. Mathematical approaches of using the more general Weibulltype model for estimating the lethality of non-isothermal dynamic processes also have been reported by several researchers (Chen et al, 2007;Corradini et al, 2005;Halder et al, 2007;Mafart et al, 2002;Peleg et al, 2001;Peleg and Penchina, 2000). However, in almost all these publications the survivor data used in the calculation were taken either from the published literature, or generated artificially by simulation.…”

Assessment of the uncertainty in thermal food processing decisions based on microbial safety objectives

“…doi:10.1016/j.jfoodeng.2010.08.027 agents and their hazard potential (Unnevehr and Jensen, 1999). The elimination of microbial spoilage and safety risks by thermal processing requires knowledge of the statistical distribution of those risks and the variability of the process applied (Halder et al, 2007;Lenz and Lund, 1977;Lund, 1978;Smout et al, 2003Smout et al, , 2000a. A similar approach is necessary when estimating the microbial shelf-life of refrigerated foods (Chotyakul et al, 2010).…”

Calculation of the total lethality of conductive heat in cylindrical cans sterilization using linear and non linear survival kinetic models

“…This can result in inconsistencies or discrepancies between survival ratios calculated by the traditional method and those actually accomplished (e.g., Campanella & Peleg, 2001;Datta, 1993). The merits and shortcomings of the traditional methods to interpret the shape of isothermal survival curves and calculate sterility have been a topic of intensive debate (Halder, Datta, & Geedipalli, 2007;Heldman & Newsome, 2003;Peleg, 2006). But regardless of one's opinion on whether the use of D, z and F 0 values should continue in thermobacteriology or be replaced, it would be worthwhile to investigate the theoretical implications of using nonlinear kinetics in assessing the sterility of canned foods heated by conductive heating.…”