Adsorption of protein-coated lipid droplets onto gellan gum hydrogel surfaces

The formation of coatings on hydrogel surfaces due to adsorption of lipid droplets is important in a number of natural and industrial processes, e.g., foods, cosmetics, and pharmaceuticals. The adsorption of cationic protein-coated lipid droplets to the surfaces of anionic hydrogels was examined in this study. An oil-in-water emulsion containing cationic β-lactoglobulin-coated lipid droplets was prepared (d4,3 = 0.3 μm, ζ = +67 mV, pH 3.0). An anionic hydrogel consisting of 1 wt% gellan gum (pH 3.0) was prepared. Emulsions containing different lipid droplet concentrations (0.1–10 wt%) were brought into contact with the hydrogel surfaces for different times (0–24 h). The adsorption of lipid droplets to the hydrogel surfaces could not be explained by a typical adsorption isotherm. We found that the electrical charge on the non-adsorbed lipid droplets became less positive or even became negative in the presence of the hydrogel, and that extensive droplet aggregation occurred, which was attributed to the ability of gellan molecules released from the hydrogels to interact with the lipid droplets. These results may have important consequences for understanding certain industrial and biological processes, as well as for the design of controlled or triggered release systems.