Analysis of the induction period of oxidation of edible oils by differential scanning calorimetry

Oxidation of rapeseed and sunflower oils has been studied by differential scanning calorimetry under non-isothermal conditions and by Oxidograph under isothermal conditions for various temperatures. The parameters of an Arrhenius-like equation describing the temperature dependence of induction period have been obtained. A new method for evaluation of the parameters from nonisothermal differential scanning calorimetry measurements, based on the dependence of onset temperature of the oxidation peak on heating rate, is presented. It has been shown that the method gives parameters not affected by systematic errors. These can be used in modeling the oxidation process where the effects of oxygen diffusion, heat transfer, and evolution of reaction heat are explicitly involved. The results obtained by differential scanning calorimetry are compared with the Oxidograph measurements. The discrepancies between the results obtained by the two methods are accounted for by oxygen diffusion within the samples.