From residues to resources: Extraction of biopolymeric and bioactive compounds from winery biowaste for food packaging films

Viticultural residues represent an abundant and underexploited source of renewable biomass that can be transformed into high-value materials within a circular bioeconomy framework for the development of sustainable food packaging. In this study, grape stalks and grape pomace were valorised through the recovery of cellulose- and polyphenol-enriched fractions, respectively, and their subsequent incorporation into gelatin/PVA films. The innovation lies in the approach towards the complementary valorisation of two winery wastes through their simultaneous incorporation into the same polymeric matrix, assessing the environmental impact associated with the extraction processes and providing alternative strategies to improve sustainability. The resulting films were flexible and easy to handle with mechanical resistance above 17 MPa. The addition of cellulose resulted in films with higher UV absorption, providing protection against UV-light, while the incorporation of polyphenols promoted radical scavenging capacity (≈ 43.12 ± 7.52 %) and enabled a pH-responsive behaviour with a colorimetric response (ΔE* > 5) under alkaline conditions. This strategy combines valorisation of food-related wastes, environmental assessment and the development of food packaging films, highlighting the approach towards bioeconomy principles.