Transparent, mechanically robust and antibacterial food packaging film based on starch/PVA/citric acid/carboxycellulose nanofibers by one-pot green process.

The development of biodegradable food packaging films is urgent because of the environmental crisis of the "plastic siege", and natural polysaccharide films are promising alternatives due to their eco-friendly attributes. Starch/poly (vinyl alcohol)/citric acid/carboxycellulose nanofibers (SPCC) films were prepared by hydrogen bonding and citric acid esterification cross-linking in a simple and green one-pot method, which avoids the use of plasticizers harmful to human health. Because of the presence of carboxyl groups, the nanofibers are uniformly dispersed. The dual reinforcement of carboxycellulose nanofibers and poly (vinyl alcohol) made the tensile strength of SPCC film up to about 56 MPa, while the commercial Polyethylene (PE) film was only about 35 MPa. Meanwhile, the film had excellent antibacterial activity against Escherichia coli (≥95.5 %) and Staphylococcus aureus (≥96.6 %), water resistance, and gas barrier properties. The transparent SPCC films inhibited the browning of litchis for about 4 days and kept the appearance and physicochemical properties of plums stable for 14 days. In particular, the film was virtually biodegradable in soil after 30 days, which opens up the possibility of replacing non-biodegradable petrochemical packaging films.