Active‐intelligent packaging film developed by gelatin‐oxidized sodium alginate and blueberry anthocyanins with robust UV shielding and ammonia/ pH sensitivity

Abstract BACKGROUND Pure gelatin film lacks sufficient flexibility and functional properties, thus limiting its wide use as an intelligent packaging film. In this study an active‐intelligent packaging film (G‐OSA‐BA) was prepared based on incorporating blueberry anthocyanins (BAs) with the gelatin/oxidized sodium alginate (G‐OSA) matrices. RESULTS The synergistic effects between the covalent crosslinking G‐OSA network and the physical blending of natural anthocyanins endowed the G‐OSA‐BA film with excellent comprehensive performance. Notably, all the G‐OSA‐BA films exhibited remarkable ductility; elongation at break reached a peak value of 170.31% when adding 1.6 wt% BAs, which increased by 4.0 times compared to pure gelatin film (42.19%). Moreover, the G‐OSA‐BA films showed almost 100% ultraviolet‐blocking capacities, strong antioxidant activity (67.35% against DPPH radical) and antibacterial activity (the maximum inhibition zone was 16.97 mm against Staphylococcus aureus (+) and 14.77 mm against Escherichia coli (−)). Furthermore, moderate dosage of BAs (1.6–2 wt%) endowed the G‐OSA‐BA film with significant pH/ammonia responsiveness. When applied to monitor shrimp freshness at 4 °C, the intelligent films turned from orange in fresh shrimp to green in spoiled shrimp after ~3 days. This visual change corresponded well with objective freshness metrics, as total volatile basic nitrogen levels rose from 10.91 to 34.3 mg 100 g −1 . Finally, the practical packaging test showed that the shrimp's spoilage was delayed from ~2 days to nearly ~4 days at 4 °C with the G‐OSA‐BA film containing 1.6 wt% BAs as a wrap. CONCLUSION The produced G‐OSA‐BA film, as an active‐intelligent packaging film, has potential in real‐time monitoring of food freshness and extension of food shelf‐life aspects. © 2026 Society of Chemical Industry.