Thermoplastic starch-nanosilver-nanoclay nanocomposites: investigation of anti-bacterial effect against Escherichia coli, mechanical and permeability properties

The biopolymers based packaging materials containing nano-silver are new types of active packaging that are biodegradable and in addition, they can reduce the risk of microbial contamination in fresh and processed foods. In this research, clay (MMT) nanofillers were used for improving the mechanical properties and water vapor permeability (WVP) of the thermoplastic starch (PS) films and producing nanobiocomposites. In addition, nanosilver (AgNP) was applied for producing active antimicrobial film against Escherichia coli. According to the results of the antimicrobial test, the MMT not only did not show any antimicrobial activity but also reduced it in the films containing nano-silver. AgNP and MMT and their mixture improved barrier properties of the PS based films; In comparison to the control film, the water solubility and permeability of the PS-AgNP-MMT films were reduced about30.93 and 75.43 percent, respectively. The results of mechanical tests showed that in the films containing MMT, increasing concentration of AgNP, increased ultimate tensile strength to 5.38 MPa and reduced strain to break to 41.23 percent. Furthermore, increasing concentration of AgNP in the films containing MMT reduced UV light transmittance significantly however, increased yellowness and turbidity.