Soy Protein-Based Hydrogels: Recent Advances in Molecular Design and Functional Applications

To address the limitations of conventional polymer hydrogels in terms of sustainability and functionality, green soy protein (SP)-based hydrogels (SPHs) demonstrate significant potential. As an abundant, renewable plant protein, SP provides an ideal molecular platform for constructing high-performance, multifunctional hydrogels. This review systematically consolidates recent progress in SPHs. Firstly, the molecular fundamentals and gelation mechanisms of soy protein are analyzed in depth. Subsequently, key construction strategies, including physical, chemical, and enzymatic crosslinking, as well as composite/hybrid approaches, are comprehensively reviewed with respect to their mechanisms, advantages, and limitations. Following this, innovative applications of SPHs in biomedical, food and nutrition, environmental/agricultural, and smart material fields are highlighted. Finally, the current challenges facing research in mechanical properties, structure–property relationships, and scalable production are identified. Future directions include developing novel green crosslinking systems, deepening multi-scale structural control, and advancing smart integrated design. This review aims to provide researchers with a systematic knowledge framework spanning from “molecular understanding” to “functional customization,” thereby propelling soy protein hydrogels toward higher toughness, intelligence, and sustainability.