pH Regulates the Network Structure and Intermolecular Interactions of Whey Protein Isolate-Oxidized Konjac...

This study aimed to investigate the effects of pH (2-10) on the physicochemical properties, gelation behaviors, microstructural characteristics, and intermolecular interactions of the heat-induced whey protein isolate-oxidized konjac glucomannan (WPI-OKGM) composite gels. Results showed that pH significantly modulated the formation and performance of the WPI-OKGM composite gel system. With increasing pH values, the particle size and turbidity of the gel pre-solutions decreased. Gel samples prepared at pH 4 and pH 8 exhibited optimal overall performance, including high hardness, superior water holding capacity, and different structures (particulate at pH 4 and fine-stranded at pH 8). At pH 6, near the isoelectric point of WPI, gels formed heterogeneous granular structures dominated by protein aggregation, exhibiting high whiteness and moderate hardness and chewiness. In contrast, strong acid or alkali environments (pH 2 and pH 10) disrupted gel network integrity, leading to deteriorated textural properties and reduced structural stability. Hydrophobic interactions and hydrogen bonding dominated gel network stabilization at pH 2, while hydrophobic interactions and disulfide bonds contributed equally at pH 4. Disulfide bonds became the core stabilizing force as pH further increased, particularly under alkaline conditions. These findings indicated that an appropriate pH promoted WPI-OKGM gel formation, providing a reference for the targeted design and application of WPI-based gel materials in diversified food systems. PRACTICAL APPLICATIONS: This study demonstrated that pH modulated the gel network of WPI-OKGM composite gels by altering the charge characteristics and intermolecular forces between WPI and OKGM. These findings provide theoretical guidance for designing WPI-OKGM composite gels with tailored properties for specific food applications, such as in acidic beverages or neutral dairy products.