Impact of Quercetin on the Functional and Structural Properties of Chitooligosaccharide (CHOS)-Enriched Surimi

This study evaluated the impact of varying quercetin (Q; 0.01-0.05%) incorporations on the quality, functional, structural, and bio-functional properties of CHOS-enriched (0.75%; w/w) pangasius surimi gel. Gel samples were analyzed for gel strength, texture profile, colour, water-holding capacity (WHC), protein interactions, structural changes, thermal stability, antioxidant/antimicrobial activities, and sensory parameters. Results indicated that Q significantly decreased pH while exerting a minor effect on proximate composition. Incorporation of Q up to 0.04% (Q4) remarkably improved breaking force (654.70 g), deformation (1.13 cm), gel strength (707.82 g cm), hardness, and WHC (90.66%), while reducing expressible moisture content and proteolysis. Molecular interactions, FT-IR spectra, SDS-PAGE, and SEM confirmed that Q promoted cross-linking of myosin heavy chains via hydrogen bonding and hydrophobic interactions, creating a denser, more compact gel matrix with higher thermal stability. Additionally, Q addition significantly enhanced 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS)/2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in a concentration-dependent manner, though lightness and whiteness indices decreased due to Q's natural yellow pigment.