Green fabrication of antimicrobial film for food preservation by polysaccharides from Poria Cocos

Recently, polysaccharide-based film materials have attracting widespread attentions due to their safety, biodegradability, and film-forming properties. However, the limited UV resistance, antibacterial and mechanical properties of polysaccharides severely restrict their application in food packaging. This work developed a biocomposite film (PGF@Ag) consited of a natural β -glucan from Poria Cocos (PCPA), in-situ synthesized AgNPs and glycerol, showing good antibacterial and antioxidant properties as well as biocompatibility and mechanical properties. Poria Cocos is an edible Chinese medicine, and its residue is rich in polysaccharide. In this system, the large amont of hydrogen groups on PCPA help fast reduce Ag + to Ag 0 in alkalescent solution and the triple-helix conformation of PCPA hinder the aggregation of AgNPs, leading the ultra small size of 9.0–12.3 nm and better ABTS radical scavenging rates of 93.30 ± 0.13 %. Additionally, the hydrogen bonding interactions between glycerol and polysaccharides significantly enhance the mechanical properties of the PGF@Ag films. The tensile strength is measured at 5.94 ± 0.5 MPa, while the elongation at break reaches 128.77 ± 12.45 %. Furthermore, the Young's modulus is recorded at 15.75 ± 1.91 MPa. Finally, the resulting films (PGF@Ag) exhibited excellent preservation effect on grapes, as reduced weight loss reduction of 14 %, hardness reduction of approximately 5.2 % over 12 days. This work provided a new strategy of sustainable constructing antibacterial films, showing great potentials for food preservation and packaging applications.