Chitosan and alginate/Aspergillus flavus-mediated nanocomposite films for preservation of postharvest tomatoes

The isolated Aspergillus flavus NSRN22 was used for green synthesis of silver and selenium nanoparticles (AgNPs and SeNPs). New food packaging films produced by combining each type of NPs with chitosan (CS) or sodium alginate (SA) were characterized. Transmission electron microscopy revealed that the average particle size was lower in case of AgNPs (9 to 14.7 nm) than SeNPS (36.8 to 53.5 nm). FTIR revealed a stronger connection between CS and NPs compared to SA and NPs. Tensile strength of CS (0.55 MPa) or SA (2.42 MPa) increased to 3.82, 4.73, 5.96, and 3.87 MPa for nanocomposite films of CS/AgNPs, CS/SeNPs, SA/AgNPs, and SA/SeNPs, respectively. Contrarily, water vapor pressures of SA (2132.57 g/m².day) and CS (2021.71 g/m².day) decreased to 1922.47, 1871.45, 1822.95 and 1795.29 g/m².day for SA/AgNPs, SA/SeNPs, CS/AgNPs and CS/SeNPs, respectively. The respective statistical minimum inhibitory concentrations for SA/AgNPs, CS/AgNPs, CS/SeNPs, SA/SeNPs, CS and SA were 1000, 1018, 1030, 1055, 1130 and 1135 μg/5 mL. CS/SeNPs were superior in terms of thermal stability (21 % weight loss), antioxidant activity (58.75 %), and normal cells viability (100 %). They demonstrated excellent preservation of tomatoes' natural color and texture, significantly reduced mold growth, and thus are ideal as antimicrobial and safe packaging materials.