Valorization of Green Banana Peel Waste into Starch–Glycerol Biodegradable Films: Optimization and Physicochemical Characterization

Abstract

The growing demand for sustainable alternatives to conventional plastic packaging has promoted the development of biodegradable materials derived from agro-industrial residues. In this study, starch extracted from green banana peel waste was used to produce biodegradable starch–glycerol films for food-packaging applications. Nine film formulations (PPM1–WP6) were prepared using starch obtained through different extraction approaches, including parenchyma-only and whole-peel processing, with and without sodium metabisulfite treatment. The extracted starches were characterized through proximate composition analysis, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The resulting films were evaluated for structural, thermal, mechanical, and barrier properties using FTIR, X-ray diffraction (XRD), SEM, dynamic mechanical analysis (DMA), water vapor permeability (WVP), and water solubility (WS). The films exhibited characteristic starch functional groups, semicrystalline structures, thermal degradation temperatures ranging from 283 to 302 °C, and viscoelastic behavior associated with plasticized polymeric matrices. Increasing glycerol concentration improved film flexibility, whereas sodium metabisulfite treatment enhanced mechanical strength. Films prepared from whole-peel starch showed higher WVP and WS values than those obtained from parenchyma starch. A randomized factorial design was used to optimize film performance for maximum tensile strength and minimum water solubility. Among the evaluated formulations, PPM2 (4% starch with sodium metabisulfite treatment) was identified as the optimal formulation and was statistically validated. These findings demonstrate the potential of green banana peel waste as a sustainable source of starch for developing biodegradable films with promising applications in food packaging.