pH-driven self-assembly of egg white protein microgel/pectin composite particles for stabilizing high internal phase Pickering emulsions.

Native egg white protein (EWP) exhibits limited emulsifying properties. In this study, egg white protein microgel (EWPM) particles were fabricated via thermal homogenization process and subsequently modified with high methoxyl pectin (HMP) to develop a novel food-grade Pickering stabilizer. The self-assembly mechanisms and emulsifying properties of the EWPM-HMP composite system were systematically investigated by modulating pH and HMP concentration. Results revealed that the interactions were highly pH-dependent. At pH > 5.0, electrostatic repulsion maintained the biopolymers in a co-dissolved state. At pH 5.0, synergistic electrostatic attraction, hydrophobic interactions, and hydrogen bonding drove the formation of stable and soluble EWPM-HMP. At pH < 5.0, strong electrostatic attraction induced the formation of insoluble aggregates. Further optimization demonstrated that a 0.2% HMP concentration saturated the EWPM surface, achieving balanced amphiphilicity (contact angle of 80.4°) and optimal interfacial coverage. Under these conditions, the composite particles exhibited the lowest interfacial tension and maximum emulsifying activity and stability, successfully stabilizing high internal phase Pickering emulsions (HIPPEs, oil fraction = 0.75, v/v) with the smallest droplet size of 36.21 μm. Confocal laser scanning microscopy confirmed that EWPM-HMP formed a dense, robust physical barrier at the oil-water interface. This study deepens the understanding of protein-polysaccharide self-assembly at oil-water interfaces and establishes a theoretical foundation for developing novel EWP-based stabilizers for advanced food emulsion systems.