Distribution of different forms of metal ions in Antarctic krill (Euphausia superba) oil: A mechanism of their pro-oxidant effects relating to association colloids

Due to the fact that association colloids were formed in krill oil, the oxidation mechanism of krill oil was more complicated. In this study, water-soluble ferrous sulfate (Fe 2 (SO 4 ) 3 ), oil-soluble ferrous fumarate (C 54 H 99 FeO 6 ) and insoluble ferric oxide (Fe 3 O 4 ) were added to krill oil and stored at 60 °C for accelerated oxidation. Peroxide value, thiobarbituric acid reactive substances and aldehyde content showed that Fe 2 (SO 4 ) 3 had a stronger pro-oxidative effect. This was caused by the fact that water-soluble Fe 3+ was mainly accumulated in extremely high content at oil-water interface of association colloids. In contrast, oil-soluble C 54 H 99 FeO 6 was mainly distributed in the oil phase. Lipidomic analysis revealed that, phospholipids were rapidly catalytically decomposed by water-soluble Fe 3+ at the oil-water interface and produced lipid hydroperoxides and free radicals. Subsequently, the produced free radicals could enter the oil phase and set off a chain reaction of free radical formation, and then promote the oxidation of glycerides.