Conjugates of sheep testis protein hydrolysates with plant polysaccharides: Structural characterization, intermolecular interactions, antioxidant activity and stability.

Protein-polysaccharide conjugate systems have garnered significant attention due to their ability to remodel antioxidant and stability functions in food systems through conformational rearrangement and supramolecular assembly. This study constructed STP-polysaccharide conjugates using sheep testis protein hydrolysate (STP) as the substrate with polysaccharide in Cistanche (CIP), Astragalus (ASP), and Angelica (ANP), respectively, to systematically elucidate the relationship between structural variation, dominant interaction forces, and functional properties. Multispectral analysis revealed that the coupling effect significantly altered the structure, with functionally relevant hydrophobic groups and Tyr/Trp residues being either exposed or buried. Mechanistic analysis indicated that hydrophobic interactions, hydrogen bonds, and electrostatic interactions collectively drove the assembly and stabilization of the STP-polysaccharide system, with their contributions influenced by polysaccharide type. Functional evaluation indicates that, after conjugation, the DPPH free radical scavenging rate of STP-CIP increased to 89.39%. In vitro digestion and storage stability studies demonstrated that after polysaccharide conjugation, the digestibility index increased to over 75.18%, and the decrease of α-helix during storage was slowed, regulating the structural integrity of the system. These findings provide a basis for the structure-interaction-function oriented design of animal-derived protease hydrolysate-plant polysaccharide conjugate systems, offering references for developing multifunctional food ingredients with both antioxidant properties and stability.