Interpenetrating network hydrogels based on soy protein isolate and sanxan: Structure, mechanical properties, and...

The poor mechanical properties and freeze-thaw stability of soy protein hydrogels limit their application in meat analogue products. In this study, we developed an interpenetrating polymer network (IPN) hydrogel composed of two crosslinked biopolymers: soy protein isolate (SPI) crosslinked by transglutaminase, and sanxan crosslinked by cations. The presence of sanxan altered the secondary structure of SPI. The dominant molecular interactions in the composite gels were disulfide bonds and hydrophobic interactions. As the sanxan concentration increased, the mechanical properties of the composite hydrogels initially increased but then decreased. At an optimized SPI and sanxan composition (10 %/0.6 % w/v), the composite hydrogels exhibited the highest degree of crosslinking (Q = 49.92), Young's modulus (20 kPa), freeze-thaw stability (16.5 % syneresis), and the lowest phase transition temperature (-18.8 °C). Additionally, these hydrogels exhibited the least change in water mobility, porosity, stress-strain profile, and viscoelasticity after freeze-thaw treatment. This was due to the ability of sanxan to delay water crystallization during the freeze-thaw process. This study provides a promising strategy for enhancing the performance of plant-based meat analogues through improved mechanical and freeze-thaw stability.