Prediction of vitamins loss during non-isothermal heat processes and storage with non-linear kinetic models

The isothermal degradation kinetics of vitamins in stored and heated foods can be described by the Weibullian–power law model, C(t)/C0=exp[−b(T)tn]C(t)/C0=exp[−b(T)tn] and the temperature dependence of b(T  ) by the log logistic equation, b(T)=loge{1+exp[k(T−Tc)]}b(T)=loge{1+exp[k(T−Tc)]}. The resulting three degradation parameters, n, Tc and k, can be used to predict the vitamins' degradation patterns under a variety of non-isothermal temperature histories, using a rate model that unlike the traditional Arrhenius and log linear model does not require that the logarithmic degradation rate must be only a function of temperature and hence time independent. Instead, the described model has been constructed on the assumption that the momentary logarithmic degradation rate is the isothermal rate at the momentary temperature, at a time that corresponds to the vitamin's momentary concentration. In all the examined cases, the proposed model's predictions were in agreement with the experimental observations.