Fabrication of functional micro-clusters by heteroaggregation of oppositely charged protein-coated lipid droplets

This manuscript describes the formation and characterization of colloidal dispersions formed by heteroaggregation of oppositely charged protein-coated lipid droplets. Micro-clusters were formed by mixing a dilute dispersion of β-lactoglobulin-coated lipid droplets (d32 ∼ 0.18 μm, 0.1 wt%) with a dilute dispersion of lactoferrin-coated lipid droplets (d32 ∼ 0.14 μm, 0.1 wt%) under conditions where the two proteins had opposite charges (pH 7). The mean particle diameter, electrical charge, and microstructure of the mixed dispersions were measured as a function of particle ratio (0–100%) and ionic strength (0–400 mM NaCl). The characteristics of the micro-clusters formed depended on the ratio of positive-to-negative droplets and ionic strength. In the absence of salt, the largest clusters were formed at intermediate particle ratios (40–60%). In a mixed system (40% LF; 60% BLG), large clusters were formed at low ionic strength due to strong electrostatic attraction between oppositely charged droplets. These clusters partly dissociated at intermediate ionic strengths due to reduction in electrostatic attraction. However, further aggregation occurred at high ionic strengths due to reduction in electrostatic repulsion. Micro-clusters may be useful functional ingredients to modulate the physicochemical properties of products in the food, agrochemical, personal care, and pharmaceutical industries, such as release characteristics, rheology, and stability.