Structure-function mechanism of TGase-induced soy-potato protein gels enhanced by ultrasound-pH shift treatment

This study investigated the effects of transglutaminase (TGase) on the properties of potato protein isolate-soybean protein isolate (PPI-SPI) composite gels before and after ultrasound-assisted pH-shift pretreatment. Compared to unmodified gels, modified potato protein isolate-soybean protein isolate (MPPI-SPI) composite gels exhibited larger particle size, lower free sulfhydryl contents, greater β-sheet proportions, and a higher fraction of covalent bonds, enhanced molecular unfolding and improved TGase accessibility. The optimal gel performance was observed at 20 U/g TGase, where modified gels showed superior textural properties and a water-holding capacity of 95.14 %. Rheological analysis revealed higher G' values for the modified gels, confirming improved elasticity and network integrity. Microstructural observations further demonstrated that pretreatment produced a denser and more homogeneous gel network. These findings elucidate the crucial role of ultrasound-pH-shift pretreatment in promoting TGase-induced gelation and provide a theoretical basis for the developing high-performance dual-protein plant-based food gels.