Development of a Multifunctional Chitosan-Based Composite Film from Crab Shell (Portunus segnis) and Algae (Ulva lactuca) with Enhanced Antioxidant and Antimicrobial Properties for Active Food Packaging

Eco-friendly, bioactive and edible films from renewable resources are increasingly regarded as viable replacements for petroleum-based packaging. This study investigates the application of <i>Ulva lactuca</i> macroalgae powder (ULP) as an active additive in crab (<i>Portunus segnis</i>) chitosan-based films for natural food packaging. Films with ULP concentrations of 0.5, 1.5, and 2.5% were prepared using a solvent-casting method with glycerol as a plasticizer. Their physicochemical, mechanical, functional, and biological properties were evaluated comprehensively. Fourier-transform infrared spectroscopy revealed intermolecular interactions between ULP's polyphenolic compounds and the chitosan matrix, enhancing the films' structural integrities. ULP's incorporation reduced the moisture content, water solubility, lightness (L*), redness (a*), and whiteness index values while significantly (<i>p</i> < 0.05) increasing the yellowness (b*), total color difference (ΔE), yellowness index (YI), tensile strength (TS), and elongation at break (EB). The antioxidant activity improved in a concentration-dependent manner, as evidenced by the high free-radical scavenging capacity. Moreover, antimicrobial tests showed significant inhibitory effects against pathogenic strains. Biodegradability tests confirmed that the films decomposed entirely within 12 days under soil burial conditions, reinforcing their environmental compatibility. These results highlight the multifunctional potential of chitosan-ULP composite films, combining enhanced mechanical properties, bioactivity, and sustainability. By utilizing renewable and biodegradable materials, this work contributes to reducing waste and promoting resource efficiency, aligning with the principles of a circular economy and environmental preservation.