Modeling of α-tocopherol loss and oxidation products formed during thermoxidation in triolein and tripalmitin mixtures

The degradation of α-tocopherol and the formation of α-tocopherol and triacylglycerol oxidation products at high temperatures (150-250°C) over a heating period (0-4 h) for a model system ranging between triolein and tripalmitin were modeled by use of an experimental design. The oxidation products of α-tocopherol formed under these conditions were α-tocopherolquinone (1.4-7.7%) and epoxy-α-tocopherolquinones (4.3-34.8%). The results indicate a very high susceptibility of α-tocopherol to capture peroxyl radicals upon oxidation, leading to the formation of polar tocopherol oxidation products. Both α-tocopherolquinone and epoxy-α-tocopherolquinones were not stable upon prolonged heating and were further degraded to other unknown oxidation products. The kinetics of αtocopherol oxidation were significantly influenced by the triolein/tripalmitin ratio. By increasing the level of triacylglycerol unsaturation the rate of α-tocopherol recovery after heating increased significantly from 2.2 to 44.2% whereas in the meantime triacylglycerol polymerization increased from 0 to 3.7%.