Complex coacervates of pH shift-modified walnut protein isolate and sugar beet pectin: Characterization and formation mechanism

The application of walnut protein isolate (WPI) in food processing is limited by its poor solubility. This study explored the characterization and formation mechanism of complex coacervates formed by pH shift-modified walnut protein isolate (HWPI) in combination with sugar beet pectin (SBP). The results showed that pH shift modification enhances the molecular flexibility and functional properties of the protein compared to the WPI without modifications. The optimal conditions for complex coacervate formation were found at pH 5 with a HWPI to SBP ratio of 7:1, where the strongest electrostatic interactions and highest turbidity were observed. The binding process was spontaneous under these conditions, influenced by thermodynamic factors. Complex coacervates demonstrated the highest turbidity at pH 5, 65°C, and NaCl concentration of 150 mmol/L, while the emulsifying activity (EA) and emulsifying stability (ES) were optimal at 25°C. This study introduces a novel approach for utilizing WPI in food applications.