Enhancing soy protein isolate gels: Combined control of pH and surface charge for improved structural integrity and gel strength

The application of sophisticated technologies to enhance soy protein isolate (SPI) gelation in the industry faces limitations due to high costs and technical intricacies. This investigation examined how different combinations of pH pretreatment and NaCl concentration affect the gel properties of SPI. Decreasing pH and increasing NaCl concentration caused soy protein particle sizes to increase in the solution due to reduced electrostatic repulsion. Additionally, decreasing pH and increasing NaCl concentration reduced the absolute zeta potential, promoting particle collisions and aggregation in SPI solutions and influencing gel strength. Rheological studies showed that lowering pH levels decreased gelation temperatures and increased gel strength. However, extreme pH levels compromised gel integrity, impacting water-holding capacity and microstructure. Supplementing SPI pretreated at pH 6.0 with 100 mM NaCl notably boosted the gel strength compared to other pretreatment methods. Further solvent analyses revealed that interactions governing gel strength-hydrogen bonding and hydrophobic interactions emerged as crucial contributors. This comprehensive investigation sheds light on the intricate interplay of factors influencing SPI gel formation, providing crucial insights for future industrial-scale applications.