AgNP anchored carbon dots and chitin nanowhisker embedded soy protein isolate films with freshness preservation for active packaging

Abstract

Biodegradable substitutes to the commonly practiced packaging materials are always in high demand. Active biopolymer film was obtained from soy-protein isolate (SPI) and the antibacterial properties were introduced by incorporating silver nanoparticles. Active bio-composite films incorporating silver nanoparticles (AgNP) are much sought after in the food packaging industry owing to their ability to extend the shelf life of fresh foods. But the toxicity of the ingredients used for preparation (mainly the reducing agents) and the poor stability limits their usage for the aforementioned application. Herein, to counter these limitations, we have adopted an environment-friendly method where carbon dot (CD) prepared from soy protein isolate was used to prepare AgNPs. AgNPs (1% wt.) and different concentrations of chitin nano whisker (CNW) (2–10% wt.) were added to soy protein isolate to fabricate nanocomposite films. The subsequent effect on the latter’s tensile property, moisture content, thermal property and morphological characteristics were noted. Here, for the first time, the steam explosion technique was used for the preparation of CNW which resulted in highly crystalline CNW with good antibacterial properties. It was observed that the mechanical strength and thermal stability of SPI film were significantly increased and the moisture content decreased with the addition of CNW and AgNP. The synergistic effect of AgNP and CNW imparted excellent antioxidant, antibacterial and antifungal properties to the SPI film thus enabling the SPI film to extend the shelf life of the food material that was packed using the same. Commercial production of such SPI films would revolutionize the food packing industry given its health benefits and its cost-effectiveness.