Abstract
The effects of gallic acid and soya lecithin on the decomposition of tocopherol (Toc) in oils by oxidation products (oxidized fatty acids, OFA: fatty substances insoluble in petroleum ether) present in soybean oil were investigated. Olive and soybean oils containing OFA and/or gallic acid and soya lecithin were heated in a Pyrex glass tube (2.7×20 cm) at 180°C. Residual Toc was determined by HPLC. Decomposition of Toc in the oils and methyl oleate was apparently promoted by the addition of OFA, but gallic acid and soya lecithin suppressed the thermal decomposition of Toc by OFA. After complete decolnposition of Toc in olive oil, hardened rapeseed oil, soybean oil or methyl oleate by heating, gallic acid and soya lecithin were added and heating was again carried out at 180°C. Small amounts of Toc monomer-like material appeared in these oils during reheating. The retention time (HPLC), Rf value (TLC) and absorption maxima of the Toc monomer-like material were the same as those of standard Toc. From the above results, it was concluded that the Toc monomer is regenerated from oxidative products of Toc by gallic acid and soya lecithin.
