Dual-Protein Systems in Foods: Structure-Function Relationships, Nutritional Impacts, and Applications.

Growing demand for sustainable, nutritious, and high-quality protein foods has highlighted limitations of single-source proteins and promoted interest in dual-protein systems (DPS). DPS are edible protein matrices intentionally formed from two distinct primary protein components, derived from different biological sources or complementary protein fractions, and processed within a shared physicochemical environment. This review integrates their definition, fabrication strategies, interaction mechanisms, functional properties, nutritional implications, and food applications. Protein-protein interactions, including electrostatic, hydrophobic, hydrogen-bonding, and disulfide-mediated interactions, regulate unfolding, aggregation, interfacial adsorption, and network formation. Processing methods such as blending, co-precipitation, ultrasound, microwave treatment, pH shifting, fermentation, germination, and enzymatic cross-linking further modify structure and functionality. These changes affect solubility, emulsification, foaming, gelation, rheology, digestibility, and storage stability. Nutritionally, DPS may improve amino acid complementarity, digestion behavior, and bioactive peptide release, but their benefits depend on protein source, ratio, processing conditions, and matrix. Applications in meat and seafood analogues, dairy-like systems, bakery products, beverages, and structured foods show potential for quality and sustainability improvement. However, sensory defects, allergenicity, limited digestibility evidence, and insufficient consumer studies remain challenges. This review provides a framework for designing stable, nutritious, sustainable, and acceptable dual-protein foods.