Development and evaluation of anthocyanin-betacyanin colorimetric films for real-time monitoring of the freshness of different meats

Background: Food spoilage, particularly in meat products, presents a significant economic and health concern, necessitating the development of reliable and user-friendly monitoring methods. Aim: This study presents the development and evaluation of novel colorimetric films for real-time monitoring of meat freshness. Methods: Films were formulated using anthocyanin (AHO) and betacyanin (BTA) from purple cabbage and red dragon fruit, respectively, embedded within polyvinyl alcohol and carboxymethyl cellulose matrix. Two pigment ratios, AHO:BTA (1:3) and (3:1), were compared to evaluate mechanical properties, antioxidant activity, and ammonia sensitivity. Results: The AHO:BTA (1:3) film demonstrated higher tensile strength, whereas the (3:1) film exhibited greater antioxidant capacity and ammonia responsiveness. Colorimetric changes were assessed across the pH range, showing sensitivity to pH shifts. The films were then applied to beef, lamb, fish, and pork samples, and their color alterations during storage under ambient and refrigerated conditions were correlated with total volatile basic nitrogen and pH levels. Conclusion: The results show a strong correlation between film color changes and established meat spoilage indicators, demonstrating the potential of these natural pigment-based films for effective, nontoxic, and visual monitoring of meat freshness.