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

Abstract

The degradation of alpha-tocopherol and the formation of alpha-tocopherol and triacylglycerol oxidation products at high temperatures (150-250 degrees 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 alpha-tocopherol formed under these conditions were alpha-tocopherolquinone (1 .4-7.7%) and epoxy-alpha-tocopherolquinones (4.3-34.8%). The results indicate a very high susceptibility of alpha-tocopherol to capture peroxyl radicals upon oxidation, leading to the formation of polar tocopherol oxidation products. Both alpha-tocopherolquinone and epoxy-alpha-tocopherolquinones were not stable upon prolonged heating and were further degraded to other unknown oxidation products. The kinetics of alpha-tocopherol oxidation were significantly influenced by the triolein/tripalmitin ratio. By increasing the level of triacylglycerol unsaturation the rate of alpha-tocopherol recovery after heating increased significantly from 2.2 to 44.2% whereas in the meantime triacylglycerol polymerization increased from 0 to 3.7%.

Quality Characterization and Oxidative Stability of Camellia Seed Oils Produced with Different Roasting Temperatures

“…Table 4 . The Ea value of an oil is also a property of interest, as it demonstrates the delay of the initial oxidation reaction due to the bond scission that takes place to form primary oxidation products 33 .…”

Extraction and Enzymatic Modification of Functional Lipids from Soybean Oil Deodorizer Distillate

“…The highest reduction was detected at severe deodorization conditions (260 °C, 3 mbar) (Verleyen, 2002a). These experiments show that tocopherols are thermally stable compounds and probably the loss of tocopherols is due to oxidation reactions, which leads to compounds such as -tocopherol dimer quinone, 4 , 5-epoxytocopherolquinone, 7, 8-epoxy tocopherol quinone, tocopherol dimer quinone, tocopherol spirotrimer and ditocopherol ethers (Verleyen, 2001a). These compounds can be found in the finished oil and in the distillate.…”

“…A significant loss in the tocopherol mass balance in the range of 25%-35% was observed originating from technological and/or chemical origin. The loss of tocopherols can be caused either by a thermal breakdown at temperatures higher than 240 °C, by oxidation reaction or by chemical reaction such as the formation of tocopheryl esters (Verleyen et al, 2001a). Extensive analysis of vegetable oils by HPLC and comparison with synthesized tocopheryl esters did not show any adsorption in the elution region of tocopheryl esters, indicating that esters of tocopherols with fatty acids are not present in crude oils (Verleyen, 2001c).…”

Influence of the Neutralization Step on the Oxidative and Thermal Stability of Acid Olive Oil

“…Neutralization of the artificially acidified oil reduced the tocopherol contents. This reduction, determined as percentage of loss 21) was more important during neutralization with soda (48%). Tocopherol losses were lower when neutralizing with lime (loss of 7%).…”

“…The tocopherol content was measured in all samples. The percentage loss 21) in neutralized, artificially acidified oils was calculated with respect to the virgin olive oil of reference used to prepare the artificially acidified oil.…”