Autoxidation and Photosensitized Oxidation of ω-3 Oils in Nanoemulsion
Sibel Uluata, Food Technology Department, Inonu University, 44280 Malatya, Turkey
D. Julian McClements, Department of Food Science University of Massachusetts Amherst 228 Chenoweth Laboratory 100 Holdsworth Way Amherst, MA 01003 USA
Eric A. Decker, Department of Food Science University of Massachusetts Amherst 228 Chenoweth Laboratory 100 Holdsworth Way Amherst, MA 01003 USA

 Fish oil is an important source of the omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) and they are important for human health.Omega-3 fatty acids are currently under consumed by many individuals so there is interest in omega-3 fortified foods and also the food industry is interested in the utilization of nanoemulsions stabilized by natural emulsifiers..  In this study, two natural (lecithin and quillaja saponin) and two synthetic (Tween 80 and sodium dodecyl sulfate) surfactants were used to fabricate omega-3 nanoemulsion using high pressure homogenization (microfluidization).  Initially, all the nanoemulsions contained small (d from 45 to 89 nm) and anionic (ζ–potential from -8 and –65 mV) lipid droplets (pH 7). The effect of pH, ionic strength and temperature on the physical stability of the nanoemulsions system was examined. Nanoemulsion stabilized with Tween 80, quillaja saponin or sodium dodecyl sulfate (SDS) exhibited no major changes in particle size or visible creaming in the pH range of 3 to 8. All nanoemulsions were relatively stable to salt addition (0 to 500 mM NaCl, pH 7.0). Nanoemulsion stabilized with SDS and quillaja saponin were stable to heating (30 to 90 oC). The impact of surfactant type on lipid oxidation was determined in the presence and absence of the singlet oxygen photosensitizers, riboflavin and rose bengal.  Riboflavin and rose bengal accelerated lipid oxidation when compare to samples without photosensitizers. Lipid hydroperoxide formation followed the order Tween 80 > SDS > lecithin > quillaja saponin and, propanol formation followed the order lecithin > Tween 80 > SDS > quillaja saponin at 37 oC for autoxidation. The same order of oxidative stability was observed in the presence of photosensitize oxidation promoted by riboflavin. Quillaja saponin consistently produced the most oxidatively stable emulsions, which could be due to its high free radical scavenging capacity.