Fabrication and characterization of nanoemulsion-coated microgels: Electrostatic deposition of lipid droplets on alginate beads

Abstract

Nanoemulsion-coated microgels were formed by electrostatic deposition of protein-stabilized lipid droplets onto the surfaces of alginate beads. Initially, oil-in-water nanoemulsions stabilized by whey protein isolate (WPI) were fabricated using high-pressure microfluidization, and calcium alginate beads were fabricated by injection of an alginate solution into a calcium solution. The surface potential of the protein-stabilized lipid droplets changed from positive to negative as the pH was increased from 2 to 8, whereas that of the alginate beads remained negative at all pH values. Confocal microscopy, light scattering, turbidity and ζ-potential measurements indicated that a thin layer of lipid droplets adsorbed to the surfaces of the alginate beads at pH values below the isoelectric point of the proteins, which was attributed to electrostatic attraction between the cationic droplets and anionic beads. The apparent shear viscosity of emulsion-bead mixtures was appreciably higher than emulsions with the same fat content at high droplet concentrations (≥20%). This study may provide a novel approach of improving the mouthfeel and texture of foods and beverages, or of reducing the overall fat content of emulsion-based products.