Characterization of complex coacervation between chia seed gum and whey protein isolate: Effect of pH, protein/polysaccharide mass ratio and ionic strength

Electrostatic complex coacervation between chia seed gum (CSG) and whey protein isolate (WPI) under different pH values (8-1), WPI/CSG mass ratios (16:1-1:1, w/w), and NaCl concentrations (0-400 mM) was investigated. Stronger complexation occurred at relatively high mass ratios (16:1, 8:1, and 4:1) and pH below the isoelectric point of WPI. Moreover, the complexation of WPI and CSG was weakened after adding NaCl and completely suppressed at 400 mM NaCl. Complexation with CSG decreased the alpha-helix and beta-turn contents, increased the beta-sheet content, and reduced the fluorescence intensity and surface hydrophobicity of WPI. The results of phase behavior and structural alteration suggested that the strongest electrostatic interaction occurred at pH 4, mass ratio 4:1, and 0 mM NaCl. The thermal stability of WPI/CSG complex coacervates was improved in comparison with that of WPI. Furthermore, rheological data and microscopy images indicated that stronger interactions between WPI and CSG resulted in greater viscosity and viscoelastic modulus, as well as denser structures. This study offers a theoretical reference for developing innovative and functional food products via understanding the interactions between WPI and CSG under different conditions.