Optimizing texture and mechanical properties: The impact of pH-modulated metal-phenolic networks on soy protein isolate gels

This study presents the initial exploration of utilizing metal-phenolic networks (MPN) to augment the structure of soy protein isolate (SPI) gels. By employing EGCG and zinc ions to create MPN at varying pH levels (5, 7, and 9), the research investigates the impact of MPN on the texture, mechanical properties, and microstructure of SPI gels. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy demonstrated that MPN binds to SPI through hydrogen bonding and electrostatic interactions. The findings indicate that the incorporation of MPN significantly enhances the structure of SPI gels. It is noteworthy that the MPN at pH 5 is the most effective in enhancing rheological properties, showing a 4 to 5-fold increase in the storage modulus. Conversely, the MPN at pH 7 excels in strengthening the 3D network, which boosts the mechanical properties, leading to a 1.88-fold increase in compressive stress. Furthermore, the addition of MPN enhances the structural integrity, thermal stability, and water retention of SPI gels, showcasing the potential of MPN as an innovative reinforcement method for food protein gels.