Utilization of interfacial engineering to produce novel emulsion properties: Pre-mixed lactoferrin/β-lactoglobulin protein emulsifiers

The interfacial coatings around lipid droplets can be tailored in a number of ways to alter the functionality of emulsion-based delivery systems. In this study, a “premix” approach was utilized that involved mixing two globular proteins with different isoelectric points prior to emulsion formation: β-lactoglobulin (BLG) and lactoferrin (LF). The influence of environmental stresses (pH, ionic strength and temperature) on the physicochemical properties of the emulsions produced using this approach was examined. Droplets coated by BLG were unstable to aggregation near their isoelectric point (pH ≈ 5), whereas those coated by LF were stable across the whole pH range. The stability of emulsions to pH induced aggregation improved as the ratio of LF-to-BLG in the mixed systems was increased. Lipid droplets coated by either LF or BLG were unstable to aggregation at high salt concentrations (500 mM NaCl, pH 6.5), but those stabilized by mixed protein coatings (LF and BLG) were stable, which was attributed to an increase in interfacial thickness and steric repulsion. Droplets coated by BLG were stable to droplet aggregation after thermal treatment (30 to 90 °C, 0 mM, NaCl pH 7), whereas those coated by LF were highly unstable when heated above their thermal denaturation temperature. The thermal stability of the droplets depended on the amount of LF in the mixed systems. Overall, this study shows that mixtures of LF and BLG are able to modulate the physicochemical properties and stability of protein-coated lipid droplets in oil-in-water emulsions. This study provides useful information for designing emulsion-based delivery systems for use in functional food and beverage products.

► Globular proteins with different isoelectric points were used to make emulsions. ► The two different proteins were mixed prior to homogenization. ► Emulsion pH, salt and thermal stability depended on protein ratio. ► This approach may be useful for creating emulsion-based food products.