Multifunctional smart gelatin films from Rosa pimpinellifolia: physicochemical characterization, fish freshness monitoring, and in vivo antioxidant assessment

In this study it was aimed to develop, characterize, and evaluate the in vivo biological efficacy of smart and active gelatin-based edible films enriched with Rosa pimpinellifolia (RP) anthocyanin extract. Films were prepared by incorporating RP extract at varying concentrations (4%, 8%, and 12% w/w) into gelatin films. FTIR analysis showed the formation of hydrogen bonding interactions between polyphenolic compounds of RP and the gelatin matrix. The incorporation of RP significantly improved the UV-barrier capacity; however, mechanical analysis revealed a dose-dependent decrease in tensile strength due to structural disruptions in the gelatin network at higher extract concentrations. The developed films exhibited a sensitive halochromic response between the pH 1.0 and 13.0, characterized by the structural transition of anthocyanins from flavylium cations to chalcone forms. Prior to film incorporation, the biological safety and antioxidant efficacy of the free RP extract were validated in an in vivo zebrafish (Danio rerio) model, demonstrating that the extract dose-dependently mitigated AAPH-induced oxidative stress, suppressed ROS accumulation, and normalized pericardial edema. Storage trials have shown a high correlation between the total color change of the films and the microbial load, pH increase, and lipid oxidation in the fish meat. This feature reveals that the films have significant potential for use as real-time freshness indicators. In conclusion, the 4% RP, 8% RP, and 12% RP films provide a biodegradable, multifunctional, and safe packaging solution for tracing food safety.