pH-responsive polyphenol–polyester composite films for active food packaging

Food spoilage driven by oxidative stress and microbial contamination remains a major challenge in minimally processed fruits, while the development of flexible biodegradable packaging systems with regulated and responsive bioactivity remains limited. In this study, a flexible bio-based active film was fabricated by incorporating gallic acid (GA) into a biodegradable poly( L -lactide)-b-poly(trimethylene carbonate) (PLLA-b-PTMC, PLT) matrix. Intermolecular hydrogen bonding between GA and PLT induced microstructural reorganization and altered chain mobility, enabling biphasic, diffusion-controlled GA release with pH-dependent behavior. The composite films exhibited reactive oxygen species scavenging activity, dose-dependent antibacterial performance against Escherichia coli and Staphylococcus aureus, and maintained cytocompatibility at effective GA loadings. Application in a fresh-fruit preservation model demonstrated delayed browning and moderated quality deterioration during storage. These findings indicate that regulating polymer–polyphenol interactions can align release behavior with storage-induced environmental changes, contributing to oxidative and microbial spoilage control in minimally processed fruits.