# Effect of pH on the Stability of Dairy Beverages Stabilized with Soluble Soybean Polysaccharides

## TL;DR

This study explores how pH affects the stability of dairy drinks using soybean polysaccharides, finding optimal stability at pH 6–7.

## Contribution

The study reveals the pH-dependent stabilization mechanism of SSPS in dairy beverages, offering practical insights for formulation.

## Key findings

- Stability of SSPS-stabilized dairy beverages is lowest at pH 5 and highest at pH 6–7.
- At pH 5, large aggregates form due to proximity to the isoelectric point of milk proteins.
- At pH 6–7, electrostatic repulsion and steric stabilization prevent aggregation and maintain stability.

## 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.