Biobased films from ‘Annurca’ apple processing waste: Isolated cellulose and polyphenols combined for functional materials development

The circular valorization of agri-food waste into bioactive and biodegradable materials represents a key strategy in sustainable food packaging development. In this study, processing waste from the Malus pumila cv. ‘Annurca' was explored as a novel source of polyphenolic compounds and high-purity cellulose for the preparation of functional bioplastic films. A green extraction approach using natural deep eutectic solvents (NADES) enabled the efficient recovery of a polyphenolic fraction (APPf), while the residual biomass was further processed to obtain carboxymethyl cellulose (CMC) with a high degree of substitution. The structural and thermal features of cellulose and CMC were characterized by ATR-FTIR, XRD, and TGA, confirming the successful functionalization and the amorphous nature of CMC. CMC films were then produced by solvent casting, incorporating APPf at different concentrations (0, 60, 120, and 180 mg/100 mL) to enhance bioactivity. Their morphology and chemical interactions were investigated by SEM and ATR-FTIR, which confirmed uniform polyphenol dispersion within the matrix. Functionally, the films exhibited strong UV-blocking capabilities and moderate antioxidant activity, as measured by ABTS and DPPH assays. In vitro biocompatibility tests on human keratinocyte (HaCaT) and intestinal epithelial (Caco-2) cell lines showed no cytotoxic effects, supporting the safety of these materials for potential food-contact applications. This study highlights the potential of ‘Annurca' apple waste as a sustainable resource for producing bioactive, biodegradable films, contributing to circular economy principles and innovative food packaging solutions.