Interfacial engineering approaches to improve emulsion performance: Properties of oil droplets coated by mixed, multilayer, or conjugated lactoferrin-hyaluronic acid interfaces

Abstract

This study investigated the effects of different interfacial structures on the performance of oil-in-water emulsions including their physicochemical stability, lipid digestion profiles, and nutraceutical bioaccessibilities. Emulsions containing oil droplets coated by lactoferrin (LF) and/or hyaluronic acid (HA) were prepared with different structural organizations: (i) LF only; (ii) LF + HA mixtures; (iii) LF + HA bilayers; and (iv) LF-HA covalent conjugates. The bilayers were formed by depositing HA onto LF-coated lipid droplets after homogenization, while the conjugates were formed by covalent attachment of HA to LF before homogenization. The interfacial pressure, adsorption kinetics, interfacial thickness, and surface load were characterized. The physicochemical properties and stability of the four types of emulsions were also measured and compared. The covalent attachment of HA to LF reduced the surface activity of the protein, which was attributed to a reduction in diffusion rate and surface hydrophobicity. The emulsifying activity and emulsion stability index of the LF were enhanced, and the salt stability and freeze-thaw stability of LF-stabilized emulsion were improved when HA was covalently attached to it. This effect was attributed to the formation of a relatively thick (161 nm) and strongly charged (−45.8 mV) interfacial layer that increased the steric and electrostatic repulsion between the oil droplets. Emulsions with mixed, bilayer, or conjugated LF-HA interfaces gave better photostability and bioaccessibility of two encapsulated nutraceuticals (curcumin and resveratrol) than LF interfaces. Overall, however, the LF-HA conjugates were the most effective at improving the performance of the emulsions. These results suggest that interfacial engineering technologies can be utilized to enhance the performance of emulsions.