The effects of surfactant type, pH, and chelators on the oxidation of salmon oil-in-water emulsions

Lipid oxidation in emulsions is influenced by the ability of transition metals to associate with emulsion droplets. The oxidative stability of 5% salmon oil-in-water emulsion was influenced by surfactant type, with oxidation rates being greatest in emulsions stabilized by anionic sodium dodecyl sulfate (SDS) followed by nonionic Tween 20 and cationic dodecyltrimethylammonium bromide (DTAB). EDTA inhibited lipid oxidation in all the emulsions, and apo-transferrin inhibited oxidation in the Tween 20-stabilized emulsions at pH 7.0, suggesting that continuous-phase iron was an active prooxidant. Iron associated with Tween-20 stabilized hexadecane emulsion droplets could be partitioned into the continuous phase by lowering the pH to less than or equal to 4.0 or by the presence of EDTA, which could help explain why low pH and EDTA decrease lipid oxidation rates. These data suggest that iron is an important lipid oxidation catalyst in salmon oil emulsions, and factors that; increase iron-emulsion droplet interactions will increase oxidation rates.