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Influence of an anionic polysaccharide on the physical and oxidative stability of omega-3 nanoemulsions: Antioxidant effects of alginate

Salvia-Trujillo, Laura, Decker, Eric Andrew, McClements, David Julian
Food hydrocolloids 2016 v.52 pp. 690-698
antioxidant activity, antioxidants, creaming, droplet size, droplets, fish, flocculation, food matrix, hydrocolloids, iron, lipid peroxidation, lipids, microstructure, nanoemulsions, nonionic surfactants, oils, oxidation, oxidative stability, particle size, polysorbates, sodium alginate, viscosity
The aim of this study was to assess the impact of an anionic polysaccharide on the physical properties and chemical stability of omega-3 enriched nanoemulsions. Fish oil-in-water nanoemulsions stabilized with a non-ionic surfactant (Tween 80) were mixed with sodium alginate at several concentrations, and then their viscosity, creaming stability, particle size, microstructure, and oxidation were measured. The viscosity of the mixed systems (2.5% w/w of oil) increased with polysaccharide addition, and was primarily governed by the alginate rather than the oil droplets. Droplet flocculation was observed at sodium alginate concentrations exceeding 0.05% (w/w), which led to rapid creaming and an increase in droplet size due to coalescence. This effect was attributed to depletion flocculation arising from the exclusion of non-adsorbed polysaccharide molecules from the immediate vicinity of the droplet surfaces. Nevertheless, the addition of alginate (0.1% w/w) to the nanoemulsions decreased the rate and extent of lipid oxidation during storage. This effect was probably due to the ability of anionic groups on the alginate molecules to chelate pro-oxidant transition metals (such as iron) in the aqueous phase. This study highlights the potential of using alginate as a natural antioxidant in nanoemulsions; however, it also highlights the potential for this polysaccharide to promote physical instability. This information could be used to optimize the composition and structure of food matrices designed to improve the oxidative stability of polyunsaturated lipids.