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 oxid ation. 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 fro m 8 to 3, oxidation of SDS-stabilized emulsions increased, while oxida tion of Brij and DTAB emulsions were unaffected. NaCl (1.0%) decreased oxidation of the SDS-stabilized emulsion by 20% but had minimal influ ence on oxidation of Brij and DTAB emulsions. These results indicate t hat the surface charge of emulsion droplets plays an important role in their oxidative stability. (C) 1998 Elsevier Science Ltd. All rights reserved.