Impact of Emulsifiers on the Oxidative Stability of Lipid Dispersions High in Omega-3 Fatty Acids

Abstract

Lipid emulsions consist of three major regions that include the droplet interior, the droplet interfacial membrane and the continuous phase. Many compounds involved in lipid oxidation such as lipid peroxides and antioxidants are surface active meaning that they will partition at the interfacial membrane of the emulsion droplet surface. Algal or salmon oil emulsified with the cationic surfactant, dodecyltrimethyl ammonium bromide (DTAB) exhibited lower oxidation rates than emulsions stabilized with anionic (sodium dodecyl sufate, SDS) and nonionic (Brij 35) surfacants. The increased oxidation rates observed in anionic emulsion droplets is largely due to the ability of iron to interact with the emulsion droplet surface where it can catalyze the decomposition of lipid peroxides. Metal chelators are capable of removing iron from the surface of emulsion droplets and thus inhibiting the oxidation of highly unsaturated fatty acids (HUFA). Inhibition of iron catalyzed lipid oxidation can also be accomplished by manipulation of emulsion droplet charge using proteins. The ability of antioxidants to interact with emulsion droplets and thus protect highly unsaturated fatty acids from oxidation is also influenced by the interfacial properties of emulsion droplets. Thus, engineering the emulsion droplet interface to maximize antioxidant activity and minimize prooxidant-lipid interactions can be a useful technique for increasing the oxidative stability of emulsified lipids containing highly unsaturated fatty acids.