Improvement of antimicrobial and UV barrier properties in chitosan films with liquorice root and liquorice root nanocrystalline cellulose extract

In this study, biodegradable chitosan (KS) films were reinforced with licorice root aqueous extract (MKS) and nanocrystalline cellulose (NKS) derived from licorice root to develop eco-friendly, bioactive packaging materials. The objective was to enhance the films' mechanical, barrier, and antioxidant properties while maintaining biodegradability. Thickness analysis showed that the combination of MKS and NKS significantly increased film thickness (p < 0.05), whereas either additive alone had little effect. Mechanical tests revealed that NKS improved tensile strength and MKS helped flexibility, with the highest strength observed in the KS-MKS-NKS film (37.9 MPa). NKS increased water absorption due to its hydrophilic groups, while MKS strengthened intermolecular hydrogen bonding, limiting swelling. Water vapor permeability decreased significantly with both additives, suggesting improved barrier properties. UV-Vis results confirmed strong UV-blocking capacity, particularly in MKS-containing films. Antioxidant analyses showed that the KS- MKS-NKS film exhibited the highest DPPH radical scavenging activity (%71.6 ± 2.6), confirming the synergistic effect between phenolic compounds of licorice extract and NKS. No inhibition zones were observed against S. aureus and E. Coli. The combined incorporation of MKS and NKS substantially improved the mechanical strength, water vapor barrier, UV-shielding, and antioxidant performance of chitosan films, demonstrating strong potential for use in sustainable active food-packaging applications.