Impact of iron encapsulation within the interior aqueous phase of water-in-oil-in-water emulsions on lipid oxidation

Iron (Fe³⁺) was encapsulated within the internal aqueous phase of water-in-oil-in-water (W/O/W) emulsions, and then the impact of this iron on the oxidative stability of fish oil droplets was examined. There was no significant change in lipid droplet diameter in the W/O/W emulsions during 7 days storage, suggesting that the emulsions were stable to lipid droplet flocculation and coalescence, and internal water diffusion/expulsion. The initial iron encapsulation (4 mg/100 g emulsion) within the internal aqueous phase of the water-in-oil (W/O) emulsions was high (>99.75%), although, a small amount leaked out over 7 days storage (≈10 μg/100 g emulsion). When W/O/W emulsions were mixed with fish oil droplets the thiobarbituric acid-reactive substances (TBARS) formed decreased (compared to fish oil droplets alone) by an amount that depended on iron concentration and location, i.e., no added iron < iron in external aqueous phase < iron in internal aqueous phase. These differences were attributed to the impact of W/O droplets on the concentration and location of iron and lipid oxidation reaction products within the system.