Effect of ozone treatment on quality parameters and structure of vegetable oils

The effects of ozone treatment on the chemical and structural properties of hazelnut oil (HO) were investigated. The HO treated with ozone gas for 1, 5, 30, 60, 180 and 360 min. The ozone reactivity with the HO were analysed by 1H, 13C NMR, FTIR and GC. Iodine, peroxide and free fatty acid value, viscosity, colour variables were measured. Reaction products were identified according to Criegee mechanism. New signals were assigned to the rings proton of 1,2,4 trioxolane in ozonated oils in 1H and 13C NMR. The viscosity increased, whereas iodine value decreased with extended ozone treatment time. The oxidation kinetics of HO was studied by DSC at isothermal temperatures. Ea and ∆H‡ of the ozone treated oils showed a reducing trend and reflected an increased oxidation sensitivity after ozone treatment. Also, the variations in melting and cooling profile of HO with ozone treatment were examined. The melting and crystallization peaks shifted towards lower temperature and became broader. Further, emulsion activity index (EAI) and emulsion stability decreased as ozone treatment time extended. Extensive droplet flocculation occurred in the emulsions containing ozone treated oils and the emulsions exhibited more solid like behaviour when ozone treatment time increased. Key Words: Ozone, hazelnut oil, oxidation, DSC, GC, NMR .