Valorization of Blueberry Processing Byproducts for the Development of Intelligent Packaging: A Comparative Study on Biomass versus Extract Use in pH-Sensitive Films

The simultaneous challenges of plastic pollution and food waste call for sustainable materials that valorize agro-industrial residues. In this study, multifunctional chitosan-based films were developed by incorporating up to 30 wt % of mildly hydrolyzed blueberry pomace (BBP), a juice industry byproduct rich in anthocyanins and fibers. Unlike conventional approaches that rely on anthocyanin extracts, our full-biomass strategy integrates both soluble and insoluble pomace fractions directly into the chitosan matrix and benchmarks these against extract-only controls. The resulting films exhibited enhanced opacity, UV-blocking ability, and strong pH-responsive color changesattributes critical for intelligent food packaging. FTIR and SEM analyses confirmed strong interactions between BBP and chitosan, while mechanical tests revealed increased flexibility and moderate reinforcement from BBP fibers. Although both BBP and extract additions slightly reduced thermal stability and increased water solubility, they did not compromise barrier properties; BBP-loaded films maintained water vapor permeability, while extract-loaded films showed a minor increase. Importantly, BBP-containing films showed superior pH responsiveness and sustained antioxidant release over time, highlighting their multifunctionality. This work demonstrates a scalable, zero-waste packaging strategy aligned with circular economy principles through the upcycling of crustacean shell waste and fruit pomace into high-performance smart films.