Tailoring sodium alginate films with fucoidan and red cabbage anthocyanins for structural, antioxidant, and colorimetric functions in food packaging

Active and intelligent packaging extends food shelf life by providing active protection while enabling monitoring of food quality and freshness. This study hypothesized that combining a marine-derived sulfated polysaccharide (fucoidan, FU) with a plant-derived pigment (red cabbage anthocyanin, RC) in a sodium alginate (SA) matrix would exert complementary effects, providing mechanical, bio-functional, and pH-sensing functions without significantly compromising moisture barrier performance. The novelty of this work lies in demonstrating how FU and RC can be integrated within an SA film to achieve complementary structural, active, and intelligent functions in a single packaging system. RC increased tensile strength from 28.05 to 45.99 MPa ( p < 0.05), while water vapor permeability remained statistically unchanged. RC-containing films showed strong UV-shielding and reversible color transitions from red to green over pH 2–12, with visible responses to ammonia vapor within 30 min. The SA/FU/RC film showed the highest DPPH radical scavenging activity (58.14%), reflecting complementary antioxidant contribution of FU. FTIR analysis revealed non-covalent hydrogen bonding and electrostatic interactions among the film components. These findings establish a multifunctional SA/FU/RC film in which FU and RC contribute distinct but complementary functions, highlighting its potential as an integrated active and intelligent packaging platform.