New Insights into the Role of Iron in the Promotion of Lipid Oxidation in Bulk Oils Containing Reverse Micelles

Formation of physical structures, known as association colloids, in bulk oils can promote lipid oxidation. However, the cause of this accelerated lipid oxidation is unknown. Therefore, the aim of this study was to investigate whether transition metals were important prooxidants in bulk oils containing reverse micelles produced from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and water. The Fe(III) chelator deferoxamine (DFO) increased the oxidative stability of stripped soybean oil (SSO) containing reverse micelles from 2 to 7 days. Because phosphatidylcholine (1,2-dibutyl-sn-glycero-3-phosphocholine) that does not form reverse micelles is not prooxidative, these results suggest that the prooxidant activity of DOPC reverse micelles could be due to their ability to concentrate both endogenous iron and lipid hydroperoxides at the water-lipid interface, thereby increasing the ability of iron to decompose lipid hydroperoxides. DFO was also able to improve the activity of a-tocopherol and Trolox in SSO containing DOPC reverse micelles increasing the lag phase from 2 to 11 and 13 days, respectively. DOPC reverse micelles decreased iron-promoted a-tocopherol and Trolox decomposition and decreased the ability of a-tocopherol and Trolox to decrease Fe(III) concentrations. Overall, these results suggest that iron is an important prooxidant in bulk oils containing reverse micelles; therefore, finding ways to control iron reactivity in association colloids could provide new technologies to increase the oxidative stability of oils.