Chitosan-konjac glucomannan-cassava starch-nanosilver composite films with moisture resistant and antimicrobial properties for food-packaging applications

For the past few decades, there has been a considerable research interest in the area of food packaging using biopolymer-based materials. Unfortunately, the water barrier property of biopolymer films is very poor. In this study, konjac glucomannan (KGM)-chitosan films incorporated with granular cassava starch (GST) and nanosilver were prepared and characterized by FTIR, SEM, XRD, TG, and DSC analysis. Incorporation of GST has significantly improved the physicochemical properties, especially the moisture barrier properties of KGM-chitosan films. Compared to neat KGM-chitosan films, the water solubility and swelling capacity of GST incorporated films decreased with increase in starch content. The moisture absorbability, water vapor transmission rate, as well as oxygen transmission rate also reduced significantly in GST-incorporated films. Contact angle measurements revealed improved hydrophobicity of GST-incorporated KGM-chitosan films. Incorporation of nanosilver particles further improved the thermal stability, tensile strength, and antimicrobial properties. Food-contact tests showed that the migration of silver was significantly lower than the permitted level of migrating quantity of silver (10mg/L) into stored bread samples, which suggests that these KGM-chitosan-GST-nanosilver films would be safe to be used as food-packaging materials. Moreover, compared to conventional food-packaging films, these nanocomposite films also exhibited better antimicrobial activity.