Loss of tocopherols and formation of degradation compounds in triacylglycerol model systems heated at high temperature

Triolein, trilinolein and a mixture of both (1:1) were heated at 180 °C for 2, 4, 6, 8 and 10 h in the absence of tocopherols or in the presence of α-tocopherol (500 mg kg−1), δ-tocopherol (500 mg kg−1) or a mixture of α-, β-, γ- and δ-tocopherol (200–250 mg kg−1 each). Losses of tocopherols as well as increases in polymeric triacylglycerols were followed. Total polar compounds were also evaluated after 10 h heating. Results demonstrated that the antipolymerisation effect of tocopherols at high temperature depended on the degree of unsaturation affecting to a greater extent the less unsaturated substrate, triolein. The maximum effect for the three substrates was found when the tocopherol mixture was added. Interestingly, α-tocopherol losses were very rapid and independent of the unsaturation of the triacylglycerol system under the conditions used, although degradation of the substrate was significantly higher as the degree of unsaturation increased for any period of heating.