Green synthesis of silver nanoparticles using persimmon polysaccharides for enhanced polysaccharide-based film performance.

Herein, the polysaccharide-based film was prepared by using persimmon polysaccharides extraction (PPE) and sodium alginate (SA) with the synthesized silver nanoparticles (AgNPs). Firstly, PPE was used as reducing and stabilizing agents for the green synthesis of PPE-AgNPs for the first time. The synthesized AgNPs had face-centered-cubic crystal structure with an average particle size of 55.88 nm. Also, the synthesized AgNPs solution exhibited superior dispersion with yellow-brown, and showed excellent antimicrobial activity (p < 0.05). Then, with incorporating AgNPs, the SA-PPE-AgNPs film showed excellent performance, the tensile strength (TS) and elongation at break (EAB) reached 18.24 MPa and 21.94 %, the water vapor permeability (WVP) decreased to 4.91 × 10 g·m·s Pa, and significantly improved UV-vis barrier property. Moreover, the SA-PPE-AgNPs film showed excellent antibacterial activities (p < 0.05) against Escherichia coli, Staphylococcus aureus, Saccharomyces cerevisiae and Aspergillus niger, with the highest antibacterial activity against Escherichia coli (inhibition zone diameter for 16.92 ± 0.14 mm). Preservation tests on sugar oranges showed that the SA-PPE-AgNPs coating treatment maintained the good appearance and color, slowed down the loss of weight (8.34 %), firmness (8.58 N), titratable acid (decreased by 30.23 %) and total soluble solids content (decreased by 10.46 %), and kept the stability of pH (4.26) and Vitamin C (Vc) (decreased by 17.51 %) during the storage period. In summary, SA-PPE-AgNPs film was an effective method for maintaining fruit freshness instead of the traditional films.