Influence of metal-phenolic networks on the properties of soy protein isolates gels

In this study, epigallocatechin-3-gallate (EGCG) was preliminarily coordinated with three types of metal ions to form metal-phenolic networks (MPNs) solutions, which were introduced into soy protein isolate (SPI) solutions to prepare SPI-MPNs composite hydrogels. This study aims to compare the effects of different types and varying addition levels of MPNs on the structure and mechanical properties of SPI gels. Dynamic light scattering and XPS results show that MPNs increase particle sizes in the composite system , and hydrogen bonding between MPNs and SPI causes smaller SPI molecules to aggregate into larger protein clusters. Low-field nuclear magnetic resonance analysis indicates that SPI-MPNs composite gels retain more water, with the majority of the water being successfully immobilized within the gel network. Rheological and textural analysis results indicate that the presence of MPNs can form a more rigid structure, significantly enhancing the mechanical properties of the composite gels. The group of gels with the highest strength exhibited a G’ value that was 2.1 times higher than that of the SPI gels, indicating the formation of a more stable three-dimensional network structure. These findings have significant potential implications for the application of SPI-MPNs composite gels in the food industry. • EGCG and Zn 2+ , Fe 3+ , Cu 2+ are utilized in the preparation of metal-phenolic networks (MPNs). • EGCG undergoes covalent cross-linking with metal ions. • The type and additive amount of MPNs affect the structural properties of SPI. • SPI-MPNs gels exhibit superior mechanical properties and thermal stability.