Iron-catalyzed lipid oxidation in emulsion as affected by surfactant, pH and NaCl

Corn oil-in-water emulsions stabilized by sodium dodecyl sulfate (SDS), Brij 35 or dodecyltrimethylammonium bromide (DTAB) were prepared to determine the influence of surface charge on iron-catalyzed lipid oxidation. Oxidation was measured using lipid peroxides, conjugated dienes, and thiobarbituric reactive substances. At pH 6.5, initial oxidation rates were in the order of SDS> Brij>DTAB. As pH was decreased from 8 to 3, oxidation of SDS-stabilized emulsions increased, while oxidation of Brij and DTAB emulsions were unaffected. NaCl (1.0%) decreased oxidation of the SDS-stabilized emulsion by 20% but had minimal influence on oxidation of Brij and DTAB emulsions. These results indicate that the surface charge of emulsion droplets plays an important role in their oxidative stability.