Synthesis, Characterization and Application of Biofilm Incorporated with Anthocyanin extracted from Red Cabbage

Abstract

The growing environmental challenges posed by petroleum-based plastic materials have driven significant
interest in the advancement of biodegradable and stimulus-responsive materials for eco-friendly packaging
solutions. In the present work, a pH-sensitive biodegradable biofilm was developed using a polymer matrix
of chitosan (CS) and polyvinyl alcohol (PVA), enriched with anthocyanin (ATH) derived from red cabbage
(Brassica oleracea) as a naturally sourced colorimetric sensing agent. Anthocyanin pigment was isolated
through an acid-assisted ultrasonication extraction technique and uniformly incorporated into the CS/PVA
blend via a solution casting process, yielding homogeneous and mechanically flexible biofilms. The
physicochemical, structural, thermal, and surface morphological properties of the resulting CS/PVA/ATH
biofilm were comprehensively evaluated using UV–Diffuse Reflectance Spectroscopy (UVDRS), X-ray
Diffraction (XRD), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Scanning
Electron Microscopy (SEM). UV-DRS analysis confirmed the effective immobilization of anthocyanin within
the polymer network while preserving its characteristic optical absorption and pH sensitivity. XRD results
revealed a semi-crystalline structure with a dominant amorphous phase, arising from strong intermolecular
hydrogen bonding among CS, PVA, and ATH molecules. Thermal analyses demonstrated enhanced thermal
stability and well-defined degradation stages, indicating improved polymer–pigment interactions. SEM
observations showed a dense, smooth, and crack-free surface morphology, reflecting excellent film-forming
ability and homogeneous anthocyanin distribution. Complementary data from a 5-day gravimetric food
packaging trial using Biowrap-style treatment on four produce varieties was also assessed. Overall, the
integration of a renewable polymer blend with a naturally derived pH-sensitive pigment resulted in a stable,
eco-friendly, and functional biofilm. The fabricated material demonstrates considerable promise for
application in smart food packaging and continuous pH monitoring applications, presenting an eco-friendly
substitute for traditional petroleum-derived synthetic indicators.