On Models of the Temperature Effect on the Rate of Chemical Reactions and Biological Processes in Foods

Abstract

The most popular model of the temperature effect on the rate of chemical and biochemical reactions and biological processes in foods is the Arrhenius equation. Reactions and processes that have an optimal or threshold temperature, or whose rate constant versus the absolute temperature reciprocal plot is curvilinear, clearly do not follow the original Arrhenius model. Their kinetics has been described by expanded versions of the Arrhenius equation, the WLF model or log-logistic model and more recently by the Eyring–Polanyi equation. Computer simulations and re-analysis of published experimental rate–temperature relationships show that over a wide range of temperatures, the fit of the Arrhenius equation can be matched by a simpler exponential model, akin to the log-linear model used in food microbiology. This indicates that the temperature-independent energy of activation’s existence cannot be inferred from the Arrhenius plot’s linearity alone and needs independent verification. The same can be said about the Eyring–Polanyi model’s fit and the inference of a temperature-independent free energy of activation. These two models’ good fit might be primarily due to their mathematical structure and not the validity of their underlying statistical mechanistic assumptions. Similarly, the WLF model’s fit can be matched by other two-parameter empirical models that do not imply any analogy between the response of food systems to heat and the rheology of plasticized synthetic rubbery polymers. Therefore, parameters of temperature dependence models obtained by curve fitting should not be considered as having physical meaning unless verified experimentally by an independent test.