Sodium alginate/bacterial cellulose nanofibers films enhanced by ZnO nanoparticles and aqueous phase from hydrothermal carbonization for functional food packaging.

In this work, the sodium alginate (SA) and bacterial cellulose nanofibers (BCNFs) composite films doped with ZnO nanoparticles (ZnO-NPs) and aqueous phase (AP) from hydrothermal carbonization (ZnO-NPs/AP@SA/BCNFs films) were developed for potential in food packaging films. The composite films were prepared using the casting method. The incorporation of the ZnO-NPs significantly enhanced the tensile strength, thermal stability and water resistance of the composite films, while decreasing the water absorption, water solubility and water vapor transmittance. The T relaxation time of the films also showed that the water degree of freedom increased by adding ZnO-NPs. Moreover, the composite films showed good mechanical properties in a wet state with a tensile strength of 25.09 MPa, exhibited strong antioxidant activity (DPPH radical scavenging rate > 90 %) and satisfactory antibacterial (inhibition zone against E. coli and S. aureus of 17.29 mm and 16.23 mm, respectively). It also proved that AP and ZnO-NPs had a synergistic antibacterial effect. The soil-buried experiment indicated the ZnO-NPs/AP@SA/BCNFs films had good degradability. The strawberry preservation experiment showed that the ZnO-NPs/AP@SA/BCNFs films decelerated the weight loss, decay rate, pH and malondialdehyde change, efficiently keeping the freshness and delaying the shelf life of the strawberries.