Bionanocomposite films of nanocellulose with chitosan or alginate: Enhanced barrier properties and active packaging potential

In this study, two biopolymers—alginate and chitosan—were combined with nanofibrillated cellulose (NFC) at varying concentrations (5–80%) to produce alginate-NFC and chitosan-NFC bionanocomposites. FTIR confirmed the good compatibility between NFC and the biopolymers. Subsequently, the optical, physical, and barrier properties relevant to packaging applications were evaluated. The incorporation of both biomacromolecules resulted in smoother and more transparent bionanocomposites. While a low concentration of alginate (5%) reduced both tensile strength and elongation at break, significant negative effects on these mechanical properties were only observed at higher chitosan loadings (50–80%). Surface hydrophobicity, evaluated by water drop test (WDT) and water contact angle (WCA), was also enhanced, reaching WCA values of 104° and 82° with 70% chitosan and alginate, respectively. Water vapor barrier performance (50% and 90% RH) improved only with chitosan addition, whereas grease barrier properties were enhanced exclusively by alginate. These contrasting effects are attributed to differences in surface free energy: chitosan increased the dispersive component of the bionanocomposites (up to 95%), while alginate introduced a strong polar character (65–82%). The results enabled insight into the interfacial interaction mechanisms among biopolymers in bionanocomposite matrices. Finally, both biopolymers provided oxygen scavenging capacity to bionanocomposites, making them promising candidates for active packaging applications—chitosan by increasing antioxidant activity, and alginate by facilitating the immobilization of an oxidoreductase-type enzyme. • Transparent NFC-alginate and NFC-chitosan bionanocomposites were obtained. • The presence of NFC was essential for achieving improved mechanical properties. • The addition of alginate improved grease and surface hydrophobic properties. • The addition of chitosan improved hydrophobicity and barrier property to water vapor. • The addition of alginate and chitosan improved the oxygen-scavenging ability.