14B-26

W. CHAIYASIT, D. J. McClements, and E. A. Decker. Department of Food Science, University of Massachusetts, Chenoweth Laboratory, Amherst, MA 01003

Oxidation of oil-in-water emulsion droplets is influenced by the properties of the interfacial membrane surrounding the lipid core. We determined if the surfactant hydrophobic tail group size altered lipid oxidation in oil-in-water emulsions stabilized by polyoxyethylene 10 lauryl ether (Brij-lauryl) or polyoxyethylene 10 stearyl ether (Brij-stearyl). These surfactants are structurally identical except for their hydrophobic tail groups which contain 12 and 18 carbons, respectively.

Our objective was to evaluate how surfactant tail group size influences lipid oxidation rates in oil-in-water emulsions.

Emulsions were prepared by sonicating either hexadecane or salmon oil (5%) with aqueous solutions of surfactants (17 mM). Lipid cumene peroxide was used as a model lipid peroxide. Lipid peroxides, headspace propanal and headspace hexanal were used to follow lipid oxidation.

The ability of iron to decompose cumene peroxide was slightly greater in hexadecane emulsions stabilized by Brij-stearyl than Brij-lauryl at both pH 3.0 (2-6%) and 7.0 (4-7%). Oxidation of methyl linoleate in hexadecane emulsions containing cumene peroxide was 1.8- to 5-fold greater in droplets stabilized by Brij-lauryl than Brij-stearyl at pH 3. No difference in methyl linoleate oxidation was observed between surfactants at pH 7.0. Oxidation of salmon oil was greater in emulsions stabilized by Brij-lauryl than Brij-stearyl as determined by both lipid peroxides and headspace propanal at both pH 3.0 and 7.0. At pH 3.0, lipid peroxides and headspace propanal concentrations were 8-45% and 13-44% lower in Brij-stearyl than Brij-lauryl, respectively. At pH 7.0, lipid peroxides and headspace propanal concentrations were 4-34% and 2-43% lower in Brij-stearyl than Brij-lauryl, respectively.

These result suggests that surfactant hydrophobic tail group size may be a determinant in the lipid oxidation in oil-in-water emulsions and therefore could be used to alter the oxidative stability of foods.