Fabrication and Characterization of Pickering High Internal Phase Emulsions (P-HIPEs) Stabilized by a Complex of Soy Protein Isolate and a Newly Extracted Coix Polysaccharide

This study explores the fabrication and characterization of Pickering high internal phase emulsions (P-HIPEs) stabilized by soy protein isolate (SPI) and coix polysaccharide (CP) complex. CP exhibited high purity (95.29%) with a molecular weight of 5.53 × 10⁵ Da and was predominantly composed of glucose, as confirmed by monosaccharide analysis and FT-IR spectroscopy. SPI/CP complexes formed well-dispersed nanoparticles with optimal stability at 2% CP concentration, demonstrated by minimal particle size and enhanced zeta potential. P-HIPEs stabilized by these complexes showed excellent physical stability without phase separation or oil leakage, with the creaming index decreasing as particle concentration increased, reaching optimal stability at 12% SPI/CP and pH 9. Particle size and zeta potential measurements indicated smaller, more uniform droplets and intensified electrostatic repulsion under these conditions, effectively preventing droplet coalescence. Confocal microscopy revealed a dense, multilayered interfacial network formed by SPI/CP complexes around oil droplets, enhancing emulsion stability. Rheological analyses confirmed that P-HIPEs exhibited elastic solid-like gel behavior with pronounced shear-thinning and superior thixotropic recovery at 12% SPI/CP and alkaline pH, highlighting improved gel strength and structural integrity. These findings demonstrate the critical influence of SPI/CP concentration and pH on the physicochemical, microstructural, and rheological properties of P-HIPEs, offering valuable insights for developing stable emulsions with enhanced performance and applicability in food systems. Notably, the results emphasize the critical role of SPI/CP concentration and pH in achieving optimal emulsion stability and rheological properties.