Comparison of the oxidative stability of chemically and enzymatically interesterified fats

A mixture of low erucic acid rapeseed (LEAR) oil and tallow (6:4, w/w) was used for enzymatic interesterification using Lipozyme IM - a sn-1,3-specific lipase of Rhizomucor miehei, or for chemical interesterification using sodium methoxide. The starting mixture and the products of interasterification were separated by column chromatography into pure triacylglycerols (TAGs) and a non-TAG fraction containing free fatty acids, mono- and diacylglycerols. Subsequently, the starting mixture, the products of chemical and enzymatic interesterification and the pure triacylglycerols were oxidized and their oxidative stability was examined by means of DSC. The investigation showed that the purr triacylglycerols isolated from the product of enzymatic interesterification have a comparable oxidative stability to that of the TAGs prepared from the starting mixture. In contrast, the TAGs obtained from the products of chemical interesterification had inferior oxidative stability. The presence of non-TAG fraction in the interesterification products lowers their resistance to oxidation. The starting mixture had the highest oxidative stability.