Tocopherols transesterification

Liang et al. (2006) investigated the effect of natural and synthetic antioxidants on oxidative stability of crude and distilled palm oil FAME (PME). Crude palm oil contains minor components such as carotenes and a-toco-pherols that upon transesterification, yields crude PME that exhibit superior oxidative stability (OSI > 25h) compared to distilled PME (OSI - 3.5h), which does not contain minor components. Liang and colleagues therefore endeavored to improve the oxidative stability of distilled PME so that it meets the minimum OSI = 6h as specified in EN 14214 (Anon., 2003b). Natural (a-tocopherol) and synthetic (BHT and TBHQ) antioxidants were investigated in distilled PME. It was discovered that both natural and synthetic antioxidants exhibited beneficial effects on the oxidative stability of distilled PME... 

TMS ether derivatives, 280 Tobacco seed oil, 93, 94,165 Tocopherols, 138,161,271, 453, 455 Tomato, 44,458,459 Torulopsis Candida, 153,154 Totox value, 202 Trachycarpus fortunei, 79 Trading specifications for crude oils, 189 Tragopogon porrifolius, 20 Trans acids, 23,175,208, 348,470 Trans determination, 257 Transesterification, 212, 282, 478 Transition temperatures, 362, 367 Trehalose mycolate, bacterial lipids,... 

In base-catalysed transesterification, some side reactions take place. For example, the reaction of water with sodium methoxide creates sodium hydroxide that can cleave the ester bonds to form soaps. Oxidation of tocopherols and other antioxidants in alkaline media also occurs, which reduces the oxidative stability of transesterified fat. 

Enzymatic transesterification of triacylglycerols does not lead to the oxidation of tocopherols. The actual catalyst is sensitive to the presence of hydroperoxides and aldehydes, which may cause changes in the enzyme structure. This also leads to a gradual loss of its activity. 

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