Enzyme-specific modulation of rice peptide structure and alginate hydrogel functionality for food applications

This study investigated how protease-specific hydrolysis modulates rice protein hydrolysate (RPH) structure and properties to tailor rice peptide‑sodium alginate composite hydrogels. Using Alcalase, Trypsin, and Flavourzyme (E/S: 3000-10,000 U/g), Flavourzyme yielded the highest hydrolysis (43.87%) and antioxidant activity (82.1%), with minimal particle size (352.0 nm). Structurally, Alcalase most reduced ordered conformations, while Flavourzyme induced minimal changes. Composite gels prepared via glucono-delta-lactone (GDL)-induced gelation exhibited enzyme-dependent characteristics: Flavourzyme-RPH enhanced water holding capacity (97.2%) and storage modulus; Trypsin-RPH improved hardness and strength (1.8-2.3× control) via Ca²⁺ crosslinking; Alcalase-RPH showed highest resilience (0.47) but reduced strength, likely due to low-MW peptides. Microstructure confirmed RPH incorporation promoted denser alginate networks. Protease selection critically determines hydrogel functionality, enabling tailored plant protein-polysaccharide composites for food and delivery applications.