pH modulating the microstructure and physicochemical properties of curdlan-potato protein composite gels

Developing fat substitutes based on protein-polysaccharide composite gels is a key strategy for producing healthier food products. However, the physicochemical properties and microstructural organization of both curdlan (CR) and potato protein (PP) are significantly influenced by pH variations. To this end, 1 M NaOH, 1 M HCl, and 4 M HCl solutions were employed to systematically investigate the effects of different pH conditions on the gel properties, rheological behaviour, and stability of the curdlan-potato protein (CP) composite dispersion system, while concurrent characterization was performed to assess changes in microstructure and molecular interactions. The results indicated that alkaline pH conditions favoured the formation of flexible, compatible gels, whereas acidic environments promoted rigid, particulate-filled gels. However, dispersion stability was reduced near the isoelectric point (pI) of PP. Microstructural analysis revealed that under acidic conditions, a coarse curdlan framework formed and intertwined with PP to create a densely packed network. In contrast, gels prepared under alkaline conditions exhibited a less defined morphology. Increasing HCl concentration enhanced gel strength; however, strong acid treatment markedly reduced water-holding capacity (WHC) and freeze-thaw stability, whereas mild acidification had no significant effect on WHC. Under alkaline conditions, partial dissociation and molecular unfolding of components led to elevated viscosity. Conversely, highly acidic environments induced aggregation and precipitation of components, resulting in increased particle size. Both phenomena significantly reduced the ζ-potential, disrupted electrostatic stabilization, and ultimately compromised system stability. These findings offer valuable insights for the food industry in tailoring the texture and functionality of CP gels through precise pH modulation.