Tea polyphenol-mediated network proteins modulate the NaOH-heat induced egg white protein gelling properties

The crosslinked network aggregation of proteins regulates the formation and property maintenance of gels. In this study, we analyzed the influence of tea polyphenol (TP)-mediated network proteins on the formation and gel properties of NaOH-thermally induced egg white gels (EWGs). The free sulfhydryl content decreased slowly from 13.12 μmol/g pro to 10.89 μmol/g pro with the addition of TP and reduced the degradation of ovalbumin as a network protein during the formation of EWGs. With increased TP and NaOH concentrations, the surface hydrophobicity and absolute value of ζ-potentials of EWG improved obviously. The mechanical test results revealed that an increase in the NaOH concentration weakened the textural properties of EWG, while adding TP increased the gel strength from 161.38 g to 195.89 g, but the rupture strength decreased from 2144.6 g to 471.59 g. Rheological results demonstrated that EWG with TPs exhibited enhanced rigidity, an increased proportion of covalent bonds, and a more compact gel network structure than EWG without TPs. The stress relaxation results were fitted using the five-element Maxwell model, which revealed that an increase in the NaOH concentration decreased gel hardness and viscosity, whereas an increase in the TP concentration enhanced gel hardness. The increase in the NaOH and TP concentrations significantly increased the surface hydrophobicity of EWGs and promoted the rise of intermolecular forces and disulfide bond interactions. Heat modification further denatured and crosslinked the non-alkalized EW proteins, resulting in a compact protein gel network structure and improved gelation characteristics.