Abstract
This study aimed to elucidate the effect of pH on the stability of soluble soybean polysaccharide (SSPS)-stabilized dairy beverages. A single-factor experimental design was employed using model systems containing 1.0% (w/v) protein and 0.4% (w/v) SSPS, with pH values adjusted from 3 to 7. System stability was comprehensively evaluated through centrifugation sedimentation rate, particle size distribution, ζ-potential, viscosity, and LUMisizer analysis. As pH increased from 3 to 7, the stability first decreased and then increased, showing the lowest stability at pH 5 and the highest stability at pH 6-7. At pH 5, large SSPS-protein aggregates formed due to the proximity to the isoelectric point (pI) of milk proteins, resulting in increased viscosity (6.83 mPa·s) and reduced ζ-potential (-5.8 mV). Conversely, at pH 6-7, strong electrostatic repulsion and steric stabilization led to small, uniformly dispersed particles and minimal transmittance change (<5%) in LUMisizer analysis. These findings clarify the stabilizing mechanism of SSPS and provide practical guidance for pH regulation in the formulation of dairy beverages.