Sustainable food packaging: Hazelnut by-products derived carboxymethylcellulose-polyvinyl alcohol films for strawberry and fresh-cut apple preservation

The growing environmental concerns associated with plastic waste have accelerated the development of sustainable and biodegradable packaging materials. In the present study, hazelnut shell and skin, two agro-industrial by-products were valorized through the extraction of cellulose, followed by the synthesis of carboxymethyl cellulose (CMC), and incorporation into polyvinyl alcohol (PVA)-based films. The resulting PVA/CMC composite films were characterized in terms of their structural, thermal, mechanical, and barrier properties. The successful etherification of cellulose was confirmed using FTIR analysis. Furthermore, the SEM and XRD analyses revealed that changes in morphology and crystallinity varied by concentration. Films containing 2 % CMC, particularly those derived from hazelnut skin, exhibited a ~59 % increase in tensile strength and a ~48 % increase in Young's modulus compared to neat PVA. Water vapor and oxygen permeability were reduced by approximately 40 % and up to 50 %, respectively alongside a 75–86 % decrease in UV transmittance. The films were further evaluated to determine their capacity to extend the shelf life of strawberries and fresh-cut apples. A substantial improvement was observed in weight retention, alongside the maintenance of phenolic content and the preservation of color and acidity, over a 7-day storage period at 4 °C. These findings demonstrate the potential of hazelnut by-products as functional biopolymer sources for eco-friendly packaging applications, contributing to circular economy and food waste reduction initiatives.