The Weibull Model for Microbial Inactivation

The first-order kinetics for microbial inactivation was derived more than 100 years ago and is still used, although more and more researchers are aware of very common non-linear survival curves. The Weibull model is just a simple alternative to the linear model and can be used to describe convex, concave, and linear survival curves. The objective of this review is not to criticize the first-order kinetics or to praise the Weibull model. In this review, the Peleg and Mafart versions of the Weibull model were compared with emphasis on the parameters of those model expressions, the scaled sensitivity coefficients of the model parameters, and the dependency of the model parameters to each other. Secondary modeling was also considered. It was concluded that both Peleg and Mafart versions can be safely used to describe linear and non-linear (convex or concave) survival curves under constant conditions. However, concerning the secondary model, predictions under dynamic conditions, and availability of an Excel®-based workbook for this purpose, the Peleg model seemed to be one step ahead. One of the parameters of the Weibull model and the secondary model derived from this parameter could be used as an alternative to the conventional D value. This work confirms that the Weibull model can serve as the microbial survival model instead of the now obsolete linear model whatever the lethal treatment is.