Modulation of bulk physicochemical properties of emulsions by hetero-aggregation of oppositely charged protein-coated lipid droplets

This manuscript describes the formation, stability, and properties of colloidal dispersions formed by hetero-aggregation of oppositely charged lipid droplets. Micro-clusters were formed by mixing an oil-in-water emulsion containing β-lactoglobulin-coated lipid droplets (d32 ∼ 0.14 μm) with another oil-in-water emulsion containing lactoferrin-coated lipid droplets (d32 ∼ 0.14 μm). These two proteins have different electrical charge versus pH characteristics because of their different isoelectric points: β-lactoglobulin (β-Lg), pI ≈ 5; lactoferrin (LF) pI ≈ 8. The ζ-potential, mean particle diameter, microstructure, creaming stability, and perceived texture of the resulting mixed emulsions were measured. Aggregates of positively and negatively charged droplets could be formed at pH values where the two proteins had opposite charges, i.e., pIβ-Lg < pH < pILF. The characteristics of the aggregates formed depended on pH and the ratio of positive-to-negative droplets. Micro-cluster formation altered the creaming stability and textural properties of the mixed emulsions. Micro-clusters may be useful functional ingredients to modulate the physicochemical properties of food systems, such as release characteristics, mouth feel, stability, or texture.