Formation of oxidation products in edible vegetable oils analyzed as FAME derivatives by HPLC-UV-ELSD

Formation of lipid oxidation products was evaluated in dietary vegetable oils by using a novel analytical approach that consisted of derivatization of TAG into FAME and HPLC analysis with two detectors in series, UV and evaporative light scattering detector (ELSD). Three sunflower oils with different contents of oleic and linoleic acids, i.e., high-linoleic (HLSO), high-oleic (HOSO) and high-stearic high-oleic (HSHOSO), and two oils containing linolenic acid, soybean (SbO) and rapeseed (RO) oils, were heated at 40. °C and analyzed up to the total exhaustion of tocopherols. Results showed that oxidation products of linoleate were predominant in all cases, whereas no significant formation of oleate oxidation products was observed in the five oils in the presence of substantial contents of the tocopherols naturally occurring. Formation of oleate hydroperoxides and monoepoxystearates derived from oleic acid was only detected when tocopherols were exhausted in the monounsaturated oils, i.e., HOSO, HSHOSO and RO. The analysis of the main oxidation products of linoleate by the method applied proved to be a good analytical approach to evaluate the global oxidation extent of oils containing oleic and linoleic acids as the only oxidizable substrates. The method used enabled the quantitative determination of the simple hydroperoxydienes of linoleate and linolenate as a whole. Results suggested occurrence of hydroperoxy compounds other than those determined by the method in the oils containing linolenic acid, showing the low stability of simple hydroperoxydienes and their participation in further reactions. © 2014 Elsevier Ltd.Peer Reviewe