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 s canning calorimetry under non-isothermal conditions and by Oxidograph under isothermal conditions for various temperatures. The parameters of an Arrhe nius-like equation describing the temperature dependence of induction perio d have been obtained. A new method for evaluation of the parameters from no nisothermal differential scanning calorimetry measurements, based on the de pendence of onset temperature of the oxidation peak on heating rate, is pre sented. It has been shown that the method gives parameters not affected by systematic errors. These can be used in modeling the oxidation process wher e the effects of oxygen diffusion, heat transfer, and evolution of reaction heat are explicitly involved. The results obtained by differential scannin g calorimetry are compared with the Oxidograph measurements. The discrepanc ies between the results obtained by the two methods are accounted for by ox ygen diffusion within the samples.