Formulation and Characterization of Chitosan Films Incorporating Hawthorn Polyphenolic Extracts via Natural Deep Eutectic Solvents

This study develops biodegradable chitosan (CS) films plasticized with natural deep eutectic solvents (NaDES) composed of choline chloride and glycolic acid (1:3 molar ratio). The same NaDES served as an effective extraction medium for bioactive compounds from hawthorn (<i>Crataegus monogyna</i>), which were incorporated into the chitosan matrix to enhance functionality. CS films with 44-70 wt% NaDES were evaluated, and the 50 wt% formulation exhibited the optimal mechanical and barrier performance. Upon extract incorporation, this film showed marked decreases in Young's modulus (131→30 MPa) and tensile strength (24→12 MPa), relative to the extract-free counterparts, indicating enhanced flexibility. Stress-strain analyses confirmed a progressive reduction in stiffness with increasing NaDES content, evidencing its plasticizing effect. FTIR analysis revealed extensive hydrogen-bonding between CS and NaDES, alongside successful integration of polyphenolics extracted from hawthorn. Morphological analysis showed smooth, dense, homogeneous surfaces. Films exhibited strong UV absorption, with extract-loaded samples extending into the UVA and visible ranges, enhancing light-barrier properties. The presence of polyphenolic compounds enhanced the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity to nearly twice that of the neat CS films. These combined mechanical, optical, and antioxidant properties highlight the potential of these NaDES-based chitosan films for sustainable active packaging.