Development of a Novel Method to Analyse Frying Oil Degradation with Initial Oxidation Temperature

Abstract

The initial oxidation temperature (IOT) of frying oils that are rich in unsaturated fatty acids were found to shift to low temperature side by the generation of hydroperoxides through the oxidative degradation of salad oil, which is a mixture of soybean and rapeseed oils. We heated very small (1–2 mg) amounts of salad oil samples with a differential scanning calorimeter at a constant rate in air. The results showed that IOT could be an indicator of the degradation of salad oils used for frying food. In contrast, saturated fatty acids, which are found in foods such as butter, do not accumulate large amounts of hydroperoxides during degradation. Therefore, the oxidative exothermal reaction occurring in such cases is not clear, rendering our method inapplicable for saturated fatty acids. However, this method analysed the degradation behaviour of oils and fats similar to the conventional methods, i.e., by studying properties such as the acid value, kinematic viscosity, and colour difference. Therefore, conducting a market survey of the degree of degradation in fried foods might now become possible.