Development and characterization of BSA-pullulan gel matrices incorporating orange peel flavonoids: Structural interactions and antimicrobial functionality

This study investigates the molecular interactions and functionality of bovine serum albumin-pullulan (BSA-Pn) hydrogels integrated with citrus flavonoid extracts (Fs). Structural characterization via vibrational and fluorescence spectroscopies revealed noncovalent interactions, primarily H-bonding, between BSA, pullulan, and flavonoids, as confirmed by molecular docking modelling. Surface chemistry analysis revealed that increased C1s-peak intensity in BSA-Pn-Fs-9 composite, thereby indicating a structural reorganization. The hydrogel demonstrated potent an antimicrobial activity against Gram-positive ( Bacillus cereus and Staphylococcus aureus ) and Gram-negative ( Escherichia coli ) bacteria, with inhibition zones of 1.34–1.69 cm, and suppressed fungal growth ( Penicillium expansum and Aspergillus westerdijkiae ) by 40.72–43.24 %. Thermal stability of flavonoids within matrix was enhanced, as evidenced by thermal structure analysis. Antioxidant assays showed significant radical scavenging with values of 33.49–93.47 % versus free radicals scavenging, confirming preserved flavonoid bioactivity. These findings underscore the structure-function synergy of BSA-Pn-Fs composites, driven by polysaccharide-protein-flavonoid interactions, positioning them as promising candidates for bioactive and functional biomaterials/additives.