Effect of stirring on the thermooxidative stability of refined rice bran oil

The aim of this study was to find out how the refining process affects the susceptibility of rice bran oil to oxygen of air at high temperature. Samples of crude and refined rice bran oil were heated at 180 degrees C for 8 h with and without stirring in laboratory-scale experiments. After every 30 min, samples were taken for analysis. The influence of stirring on rice bran oil heat stability was related to the loss of tocopherols and sterols, and to the thermooxidative state of the samples, which was evaluated according to polymer formation and changes occurring in fatty acid composition and triacylglycerol (TAG) structure. The results demonstrated a significant loss of natural antioxidants during the heating process with stirring, accompanied by a decrease in the levels of linoleic acid (18:2) and TAG (LLO, LLP and OLO) which resulted in a substantial increase of polymer TAG. The unsaturated fatty acids in the sn-2 and sn-1,3 positions were differently affected during the heating process.