Electrospun nanofiber membranes based on dialdehyde pullulan polysaccharide and schiff base crosslinked lysozyme for antibacterial packaging of blueberries

Pullulan polysaccharide electrospun nanofiber membrane is promising in food packaging field. However, there are still some limitations in its application, due to its high hydrophilicity, poor basic properties (water and thermal stability, mechanical properties, etc.) and weak bioactivity. To solve these problems, pullulan polysaccharide was first oxidized to dialdehyde pullulan polysaccharide (DPul). Then the DPul was prepared into electrospun nanofiber membrane (DPul-M). The DPul-M was used as a green crosslinking agent, and the aldehyde group on the DPul-M and the amino group of lysozyme were reacted with each other by Schiff base to form an imine bond (C=N), thus crosslinking lysozyme to the membrane and obtaining the dialdehyde pullulan polysaccharide-lysozyme nanofiber membrane (DPul-LZ-M). After crosslinking, the basic performance of the membrane was improved and the hydrophobicity was greatly enhanced. The water contact angles can reach to a maximum angle of 108°. Meanwhile, lysozyme crosslinked on the membranes significantly enhanced the antibacterial activity of the nanofiber membrane. It can achieve the highest antibacterial rate of 95.69 % and 95.46 % against E. coli and S. aureus, respectively. The preservation test indicates that the DPul-LZ-M can extend the shelf life of blueberries. The results showed that DPul-LZ-M has good application prospects in active food packaging.