Chitosan–PVA composite films incorporated with roselle anthocyanins: Colorimetric smart sensor for real-time monitoring of meat and seafood freshness

Ensuring freshness in perishable foods like meat and seafood is vital for food safety. This study developed a biodegradable colorimetric film from chitosan–polyvinyl alcohol (Cs/PVA) infused with roselle anthocyanin extract (CPAR) to monitor spoilage. Among variants, CPAR-5 (5 mL extract) showed the highest pH sensitivity (ΔE = 44.69, S% = 42%) and rapid response to ammonia vapor. Characterization via UV–Vis, FTIR, and FESEM confirmed effective pigment integration and film structure. Applied to chicken, shrimp, and tilapia, CPAR-5 visually tracked spoilage in real time under ambient and cold storage, correlating with critical pH thresholds (≥6.8 for chicken, ≥7.4 for shrimp, ≥7.0 for fish). A visual card reader was developed for semi-quantitative freshness evaluation, demonstrating that CPAR-5 is a highly sensitive, robust, user-friendly, and environmentally sustainable smart indicator with strong potential for practical food safety monitoring and reduce food waste. • Colorimetric film developed using roselle anthocyanin and chitosan–PVA matrix. • Film shows distinct color shifts in response to pH and ammonia vapor exposure. • Enables real-time freshness monitoring of chicken, shrimp, and tilapia meats. • Card reader based on RGB analysis facilitates interpretation of freshness level.