Multifunctional chitosan films enriched with artichoke stem extract and microbial lipids for active food packaging

In response to the growing demand for sustainable and functional food packaging materials, this study reports the development and comprehensive characterization of chitosan-based biocomposite films (CS, CS-L, CS-ASE, and CS-ASE-L) incorporated with microbial lipids from Rhodotorula mucilaginosa SC4 (GenBank accession number: PZ028440) and artichoke stem extract. Fourier-transform infrared (FT-IR) spectroscopy confirmed the presence of molecular interactions between chitosan and the incorporated bioactive components, while scanning electron microscopy (SEM) revealed increased structural heterogeneity in the composite matrices. Physicochemical analyses demonstrated that lipid incorporation significantly reduced water solubility, the degree of swelling, and water vapor permeability (53.63 g/m²·day), thereby enhancing the overall barrier performance of the films. Optical characterization indicated improved light-barrier properties in extract-containing films, as evidenced by decreased L* values and a concomitant increase in opacity. From a mechanical perspective, the CS-ASE film exhibited the highest tensile strength (40.33 MPa), whereas lipid-containing formulations displayed enhanced flexibility, as reflected by increased elongation at break. Bioactivity assessments revealed that the CS-ASE film exhibited strong antioxidant capacity (DPPH: 80.07%; ABTS: 81.07%) and a high total phenolic content (447.3 μg GAE/mg). Furthermore, significant polyphenol oxidase (PPO) inhibitory activity (IC₅₀: 23.62 μg/mL) and low minimum inhibitory concentrations (MICs) (0.25-0.5 mg/mL) were observed, indicating strong antimicrobial efficacy against Escherichia coli and Staphylococcus aureus. In addition, phenolic release indicated a biphasic profile, with rapid initial release (56-70% in 30 min) followed by sustained diffusion to 1440 min, indicating non-Fickian transport. The films reduced enzymatic browning, lowering ΔE compared to controls.