Biobased films of nanocellulose and mango leaf extract for active food packaging: Supercritical impregnation versus solvent casting

Antioxidant and antimicrobial free-standing films composed of nanofibrillated cellulose (NFC) and a polyphenolic-rich extract, viz. mango leaf extract (MLE), were produced via supercritical solvent impregnation (SSI) and conventional solvent casting film-processing methodologies. The CO2-assisted impregnation of NFC with MLE created robust films with thermal stability up to 250 ?C, good mechanical performance (Young?s modulus > 4.7 GPa), UV-light barrier properties, antioxidant capacity with maximum inhibition percentage of ca. 84%, and antimicrobial activity against Staphylococcus aureus (growth inhibition ?37%) and Escherichia coli (growth inhibition ?91%). The comparison of the NFC/MLE films prepared by SSI with those fabricated via solvent casting shows a clear advantage of the SSI methodology. Particularly, the antioxidant and antimicrobial activities are visibly higher in the films fabricated by the CO2-assisted impregnation of MLE into NFC. In fact, for the SSI films, the MLE components are mostly adsorbed at the surface and not in the bulk of the biopolymeric matrix, which translates into faster migrations and, hence, higher active properties. All these findings evinced the potential performance of the NFC/MLE films prepared by the eco-friendly SSI as UV-blocking, antioxidant, and antimicrobial bio-based materials for application as sustainable active food packaging.

Automated summary

In this study, antioxidant and antimicrobial free-standing films were produced using nanofibrillated cellulose (NFC) and mango leaf extract (MLE) via supercritical solvent impregnation (SSI) and conventional solvent casting film-processing methodologies. The films fabricated by CO2-assisted impregnation of MLE into NFC showed higher antioxidant and antimicrobial activities compared to those prepared by solvent casting. These findings demonstrate the potential of NFC/MLE films as sustainable active food packaging materials with UV-blocking, antioxidant, and antimicrobial properties.