Smart active packaging films from chitosan and neem gum: Reinforcement with bentonite and anthocyanin for food packaging

Abstract

The high demand for research and development of sustainable, biodegradable alternatives to petroleum-based plastics owing to their serious environmental problems is a well-known fact. In this study, we have developed a novel smart and active packaging film using a blended polymer matrix of chitosan and neem gum. The major challenge encountered is the inherent hydrophilic nature and lower mechanical strength of biopolymers. To overcome these limitations, an ultrasound-based blending (of chitosan and neem gum) combined with chemical cross-linking using NaOH was carried out. Anthocyanin pigment serves as a visual spoilage indicator which enables consumers to visually judge the freshness of packaged food items. Characterization by FTIR verified successful cross-linking inside the chitosan and neem gum matrix. SEM imaging showed that the cross-linked films have a uniform morphology where the bentonite nanoclay is uniformly distributed. The films exhibited much better thermal stability as shown by TGA analysis. The addition of bentonite enhanced the barrier properties by decreasing oxygen and water vapour permeability due to the tortuous path formed by the clay layers. The contact angle measurements showed a clear increase from 68° to 78° showing enhanced surface hydrophobicity. The phenolic compounds in neem gum and anthocyanin showed increased DPPH scavenging activity. Colorimetric tracking showed distinct, pH dependent colour changes confirming the presence of volatile basic spoilage compounds to facilitate simple visual assessment. Application trials on paneer for 7 days showed lower drip loss and lipid oxidation (TBARS) than polyethylene controls. Soil burial tests showed significant biodegradation supporting their suitability as eco-friendly alternatives to conventional plastic packaging.