Fabrication and characterization of custard apple seed starch/ corn starch bio-nanocomposite films immobilized with chitosan nanoparticles and pomegranate peel powder for extending the shelf life of Litchi chinensis fruit

Abstract

The study aimed to develop a bio-nanocomposite packaging film by valorizing agricultural by-products, specifically custard apple seed starch (CaSS), and incorporating varying concentrations of chitosan nanoparticles (ChNPs) with corn starch (CS), carrageenan (CAR), guar gum (GUG), and pomegranate peel powder (PPP). This approach seeks to extend the shelf life of litchi and explore alternative, underutilized resources that can contribute to sustainability and add value to agricultural waste. The composite films form a dense polymer network, enhancing the packaging's attributes. However, the film-forming solution's viscosity decreases with the addition of ChNPs. Further characterization using SEM, FTIR, GC-MS, and XRD revealed improved intermolecular interactions, bioactive compounds, and crystallinity of the films. The addition of ChNPs and PPP significantly reduces moisture content and the water vapour permeability (WVP) rate of the film. The films exhibited an antimicrobial activity against Pseudomonas fluorescens and Botrytis cinerea. The developed films were tested for their effectiveness in extending the shelf life and maintaining the physicochemical characteristics of litchi. Nevertheless, films composed of CaSS/CAR/GUG without CS/PPP/ChNPs displayed discoloration, color changes, and microbial growth after 2 ± 1 days at 27 ± 2 °C and 65 ± 5% relative humidity (RH). In contrast, CaSS/CAR/GUG/CS/PPP films with 3% ChNPs showed similar changes after 5 ± 1 days, effectively extending the shelf life by an additional 3 ± 1 days, reducing postharvest losses, and increasing value to the fruit industry.