Pectin/tapioca starch-based intelligent indicator films containing ZnO nanoparticles and Morus alba L. anthocyanin complexes for sustainable tuna freshness monitoring and food safety.

This study aimed to develop a multifunctional intelligent film based on pectin/tapioca starch (P/TaS) incorporating zinc oxide nanoparticles (ZnO-NPs) and mulberry anthocyanin extract (MAE) for real-time monitoring of tuna freshness. SEM and ATR-FTIR analyses confirmed excellent compatibility among ZnO-NPs, MAE, and the polymer matrix through intermolecular interactions. Increasing the MAE concentration from 0 to 12% decreased tensile strength from 11.04 to 3.63 MPa, increased water vapor permeability from 1.03 to 2.63 g·mm/m2·day·kPa and water solubility from 13.94% to 74.67%, and significantly enhanced antioxidant activity from 25.32 to 86.86%. The films exhibited distinct pH-dependent color transitions from red (pH 2) to purple (pH 6) and green (pH 12), as well as clear responses to volatile acetic acid and ammonia. Among all formulations, the film containing 9% MAE demonstrated the best balance of physicochemical properties, color sensitivity, and storage stability. The color stability of the P/TaS/ZnO-NPs/MAE-9% film was estimated to be approximately 90 days at 4 °C using the Arrhenius model. Quantitative correlations were established between the indicator color parameters (L⁎, a⁎, b⁎, and ΔE) and indicators of tuna freshness, including weight loss, pH, total volatile basic nitrogen (TVB-N), and total microbial counts. Tuna spoilage was indicated by a distinct color transition from purple to green, corresponding to increases in pH and TVB-N beyond acceptable thresholds. Overall, the P/TaS/ZnO-NPs/MAE-9% film successfully monitored tuna freshness, demonstrating the strong potential of this sustainable intelligent packaging system for real-time seafood freshness monitoring.