The activity of pectin methyl esterase (PE) in peaches during blanching treatments was modelled and analyzed. It was postulated that the enzyme exists in two configurations, one bound and one soluble. The bound configuration can be converted into the soluble configuration. These two configurations have a different susceptibility to temperature. All rate constants of reaction were modelled as dependent on temperature according to the Arrhenius law. Despite the daily measuring variance, the variance accounted for by the model in multivariate nonlinear regression analysis was more than 90%. The obtained parameter values were highly comparable for two consecutive seasons. An analysis of the data of the two seasons combined was feasible with the kinetic parameters estimated in common, without losing information with a tremendous increase in predictive power.