Air oxidation of trilinolein and the antioxidative effect of alpha-tocopherol and synergism of ascorbic acid

To examine the autoxidation of unsaturated triglycerides, experiments were carried out on purified trilinolein (TL), by introducing oxygen at 75°C into an apparatus similar to that employed previously. Methyl linoleate (ML) prepared from the same source was used for comparison. Samples were taken at various oxidation times, and several chemical constants such as peroxide value (POV), thiobarbituric acid value (TBAV), etc. were measured. The IR and UV absorption spectra were also examined. Further, the antioxidative effect of α-tocopherol (α-Toc) and the synergism of ascorbic acid (AA) were studied. α-Toc and AA (3mM/kg) were added TL, and the residual amounts of them in the course of oxidation were followed by high performance liquid chromatography. The relation between the decrease of residual α-Toc and AA and the increase of POV of TL was examined. The results obtained were as follows. The induction period of oxidation was much shorter in TL than in ML. The rate of oxidation or decomposition of peroxides was faster in TL than in ML after the induction periods. The maximum TBAV of TL was found to be about 1/3 that of ML. The antioxidative effect of α-Toc and the synergistic effect of AA were clearly observed in both TL and ML. It was observed that α-Toc and AA decreased more gradually when both were present than either one alone. The results indicate that α-Toc and AA acted as mutually protective substances, and when both disappeared at nearly the same time, POV increased rapidly.