Influence of electrostatic interactions on the formation and stability of multilayer fish oil-in-water emulsions stabilized by whey protein-xanthan-locust bean complexes

The purpose of this research was to investigate the impact of electrostatic interactions on the stability of multilayered fish oil-in-water (O/W) emulsions stabilized by whey protein isolate (WPI)-xanthan (XG)-locust bean gum (LBG) complexes. Emulsions were prepared using the layer-by-layer deposition technique with salt concentrations (0, 5, and 50 mM NaCl) at pH below (pH 3) and above (pH 7) the isoelectric point of WPI. Results indicated that zeta potential at pH 3 resulted in positive values, whereas at pH 7 resulted in negative values, with the magnitude of the zeta-potentials increasing as the NaCl concentration increased. NaCl did not have any major impact on the particle size of the emulsions. XG emulsions had the highest viscosity at pH 3 regardless of time, though XG-LBG emulsions showed a significant increase at 0 and 5 mM NaCl over time. XG emulsions at pH 3 showed the highest viscosity at every salt concentration. At pH 7, XG-LBG emulsions had the highest viscosity results, yet decreased over time, indicating the negative salt effect the synergistic interaction between XG and LBG. With 0 mM and 5 mM NaCl at pH 7, XG-LBG emulsions had the highest creaming stability; while with 50 mM NaCl, XG emulsions had the highest creaming stability. For both the primary and secondary lipid oxidation tests, XG-LBG emulsions had the highest oxidative stability at every salt concentration at pH 7. These results have important implications in the design of biopolymer-based delivery systems for microencapsulating omega-3 polyunsaturated fatty acids for use in functional foods.