Synergistic effects of tea polyphenols and phosphorylation on the gelation behavior of egg white proteins

Egg white protein (EWP) is widely used in the food industry owing to its excellent gelation properties. This study investigated the synergistic effect of tea polyphenol (TP) and sodium tripolyphosphate (STP) or sodium pyrophosphate (TSPP) on the gelation properties of EWP. Results showed that TP and phosphates enhanced the surface electrostatic formula of EWP to improve the stability of complexes. Meanwhile, STP and EWP were ligand bound as OC–N–P, whereas TSPP was bonded to EWP as P–O–P. Increase in TP content decreased α-helical content, and shifts in the β-turns and random structures of EWP were observed. TSPP enhanced the crystallinity of EWP and promoted the formation of ordered structures. The dominant forces of EWP gel (EWG) under synergistic treatment were non-specific cross-linking, ionic bonding, and hydrophobic interactions. Scanning electron microscopy (SEM) results revealed that the gel three-dimensional network cross-linking microstructures were evident, and pore size analysis showed that the EWG formed a large pore structure to contain the water molecules produced by the combination of phosphate and EWP. Evaluation of the gelation properties revealed that the synergistic effect of TP and each phosphate prolonged the gelation time of EWP and decreased the rigidity of EWG, but increased the springiness and true stress of the EWG. Simultaneously, phosphorylated and TP-treated EWGs showed reduced sensitivity to reagents and salt ions. Overall, this study provides a scientific basis for the improvement and regulation of the gelation behavior of EWP.