Study on physical and mechanical properties of the biopolymer/silver based active nanocomposite films with antimicrobial activity

Silver nanoparticles (AgNPs) were prepared by reducing AgNO₃ using biopolymer pullulan as both a reducing and stabilizing agent. The prepared AgNPs solution was blended with pectin to make active nanocomposite films. The formation of AgNPs in the solution was confirmed by characteristic surface plasmon resonance (SPR) peak of AgNPs at 400–500 nm, using UV–vis absorption spectroscopy. The prepared composite and nanocomposite films were characterized using UV, FE-SEM, and FT-IR. In addition, films color, optical, water contact angle, water vapor permeability, mechanical and antimicrobial properties were evaluated. FE-SEM analysis showed uniform distribution of AgNPs in the resulting nanocomposites films. The presence of AgNPs could affect the physical and mechanical properties of the prepared films. The color, moisture content, water vapor barrier properties, hydrophobicity, thickness, and elongation at break of the films were significantly increased after formation of composite with AgNPs, but tensile strength and elastic modulus of the films were decreased. FT-IR results indicated that AgNPs had good compatibility with biopolymers. In addition, nanocomposite films, especially pullulan/AgNPs and pullulan/pectin/AgNPs films exhibited better antimicrobial activity against food born pathogens, which suggests that prepared nanocomposite films can be used as active food packaging material to maintain food safety and to improve shelf life of the packaged food.