25The aim of this study was to assess the impact of an anionic polysaccharide on the 26 physical properties and chemical stability of omega-3 enriched nanoemulsions. water nanoemulsions stabilized with a non-ionic surfactant (Tween 80) were mixed with 28 sodium alginate at several concentrations, and then their viscosity, creaming stability, particle 29 size, microstructure, and oxidation were measured. The viscosity of the mixed systems (2.5 % 30 w/w of oil) increased with polysaccharide addition, and was primarily governed by the 31 alginate rather than the oil droplets. Droplet flocculation was observed at sodium alginate 32 concentrations exceeding 0.05 % (w/w), which led to rapid creaming and an increase in 33 droplet size due to coalescence. This effect was attributed to depletion flocculation arising 34 from the exclusion of non-adsorbed polysaccharide molecules from the immediate vicinity of 35 the droplet surfaces. Nevertheless, the addition of alginate (0.1 % w/w) to the nanoemulsions 36 decreased the rate and extent of lipid oxidation during storage. This effect was probably due 37 to the ability of anionic groups on the alginate molecules to chelate pro-oxidant transition 38 metals (such as iron) in the aqueous phase. This study highlights the potential of using 39 alginate as a natural antioxidant in nanoemulsions; however, it also highlights the potential 40 for this polysaccharide to promote physical instability. This information could be used to 41 optimize the composition and structure of food matrices designed to improve the oxidative 42 stability of polyunsaturated lipids. 43 44 Keywords: Nanoemulsions; omega-3 fatty acids; lemon oil; oxidation; sodium alginate; 45 food matrix effects 46 47
Nanoemulsion formation 132The lipid phase of nanoemulsions consisted of a mixture of fish oil and lemon oil (50:50 133 w/w). Both oils were mixed and stirred for 5 min at room temperature. The aqueous phase of 134 the nanoemulsions consisted of 100 mM acetic-acetate buffer at pH 3.0. A coarse emulsion 135 was formed by mixing lipid phase (10% w/w), Tween 80 (1% w/w), and aqueous phase (89% 136 w/w) with a high-sheer blender for 2 min at 20,000 rpm. The resulting coarse emulsion was 137 then passed three times through a microfluidizer (model M110-P, Microfluidics, Newton, 138 MA) working at 15,000 psi to form a nanoemulsion. 139