Crosslinking Soy Protein: Mechanisms, Functional Modification, Applications in Food, and Future Directions

Soy protein (SP) is a sustainable plant-based biopolymer valued for its nutrition, yet its application is often restricted by poor solubility, instability, and reduced bioavailability. Crosslinking overcomes these limitations by forming intra- and intermolecular covalent bonds, thereby altering the protein's structure and functionality. This review analyzes enzymatic (e.g., transglutaminase, laccases), chemical (e.g., genipin, tannins), and physical (e.g., high-pressure, thermal) crosslinking mechanisms. These modifications significantly enhance functional properties, including emulsion stability, gel strength, and water-holding capacity. These improvements enable advanced applications in texturized foods like meat analogs, functional emulsions, active/biodegradable packaging films, and bio-based adhesives. Despite the promising advancements, challenges regarding scalability, cost, off-flavors, and regulation persist. Future directions point towards the integration of hybrid modification techniques, AI-driven process optimization, and the development of smart, bioresponsive materials to fully realize the potential of crosslinked SP as a high-performance, sustainable ingredient in the food and industrial sectors.