Distribution of Kinetic and Thermal Processing Parameters Based On α-Amylase Inactivation Data.

Knowing the thermal inactivation kinetic parameters of microorganisms and enzymes in foods is critical to ensure final product's quality and safety. In the present work, thermal inactivation kinetics for α-amylase, produced by Aspergillus oryzae, were studied at four different temperatures of 60°C, 70°C, 80°C, and 90°C. Selected kinetic parameters, namely, the decimal reduction time, D (min), and the z value (°C), and their frequency distribution were estimated by analyzing the obtained experimental results through a stochastic Monte Carlo procedure. A proper mathematical correction to account for the initial temperature rise and the final temperature drop of the samples, using the F value concept, was employed. From 60,000 calculated paired values, the D and z values of α-amylase were found to be normally distributed with mean values estimated as 4.22 ± 0.63 min and 13.00°C ± 0.98°C, respectively, for the ±values indicating the 99% confidence interval of the estimates. As an application of the proposed procedure and its findings, the effect of the variation of the thermal inactivation kinetic parameters on lethality calculations of a thermal process was assessed. PRACTICAL APPLICATION: Stochastic analysis is useful in practical issues such as thermal processing and enzyme inactivation, characterized by nonlinear dynamics and multiple interacting variables, where efficient optimization approaches are essential. This article presents a methodology on the stochastic assessment of thermal inactivation kinetic parameters, D and z, using a Monte Carlo multiple scheme. The effect of parameter variation on lethality calculations was thereafter evaluated during in container thermal processing of a conduction and a convection heating product. For reliable lethality calculations, only the frequency distribution of each parameter is required, avoiding the necessity of having paired values of the kinetic parameters.