Structure and property based design of alginate–nanochitosan active films functionalized with patchouli oil for sustainable tuna packaging

This study reports the development of an alginate-based active edible film functionalized with chitosan nanoparticles and patchouli essential oil for the preservation of tuna fillets during refrigerated storage. Composite films were fabricated by solution casting using sodium alginate as the primary polysaccharide matrix, incorporating 1% (v/v) patchouli oil and chitosan nanoparticles at concentrations of 1%–5% (w/w). Structural and surface analyses revealed a progressive increase in surface roughness from 35.45 nm (AG) to 192.40 nm (AG/PO/NCS5), accompanied by a tunable wettability transition with contact angles increasing from 62.0° to 91.4°. Thermal stability improved markedly, with T 10 increasing from 181.6 °C (AG) to 205.6 °C (AG/PO/NCS5) and residual mass rising to 25.0%. The AG/PO/NCS5 film exhibited enhanced mechanical strength (36 MPa), superior UV-blocking (>90%), and high antioxidant activity (86.9% ABTS scavenging). Application trials demonstrated that the AG/PO/NCS5 film effectively suppressed spoilage, maintaining relatively low total viable counts (5.5 log CFU/g), psychrophilic bacterial counts (4.5 log CFU/g), and TBARS (0.6 mg MDA/kg) after 15 days of refrigerated storage, compared to higher values observed in polyethylene packaging (9.2 log CFU/g, 7.6 log CFU/g, and 1.4 mg MDA/kg, respectively), indicating improved microbial and oxidative stability of tuna fillets. Overall, these results demonstrate that rational polysaccharide functionalization can yield sustainable active packaging materials that support responsible consumption and production practices in line with SDG 12.