Structural modification of whey protein isolate via electrostatic complexation with Tremella polysaccharides and its effect on emulsion stability at pH 4.5
Yongqing Ma, Huixue Sun, Shanshan Zhang, Chenhe Yang, Elshan Musazade, Hongxiu Fan, Tingting Liu, Yanrong Zhang
Abstract
Emulsions play an important role in food systems by encapsulating and delivering active compounds, but maintaining their stability under various conditions can be challenging. This study explored how the concentrations of Tremella polysaccharides (TPs) (0–0.75 %) affects the structural of whey protein isolate (WPI) and the stability of their emulsions at pH 4.5. At this pH, electrostatic interactions between WPI and TPs exposed hydrophobic groups within the protein, increased β-sheet contents, and improved the hydrophilic-hydrophobic balance, which enhanced emulsifying performance. WPI-TPs complexes (WTS) showed a high emulsifying activity index (57.85 m 2 /g) and emulsion stability index (82.03 %). Compared to WPI-only emulsions, WTS emulsions had smaller particle sizes, lower Turbiscan Stability Index (TSI) values, and higher viscoelasticity, thermal stability, freeze-thaw stability, and re-emulsification capacity. Importantly, when the TPs concentration in WTS emulsions exceeded 0.375 %, the TSI value dropped below 1, showing no particle migration or peak thickness, indicating full emulsion stability. These findings suggest that TPs help stabilize WPI emulsions near their isoelectric point (pH 4.5) and offer a promising approach to improving WPI functionality in acidic environments. The WTS system provides a reliable way to stabilize emulsions under acidic conditions, supporting the development of natural, stable emulsifiers for food applications. • At pH 4.5, the electrostatic complexation between whey protein isolate (WPI) and Tremella polysaccharides (TPs) enhanced the stability of the emulsion. • The electrostatic interaction between WPI and TPs exposed hydrophobic groups, increasing the proportion of β-sheet structure in the secondary structure. • The emulsion formed by the WPI-TPs complex (WTS) exhibited a smaller particle size, increased apparent viscosity, and reduced droplet migration rate. • The WTS emulsion displayed improved thermal and freeze-thaw stability with increasing TPs concentration.