Nanocellulose-enhanced smart film for the accurate monitoring of shrimp freshness via anthocyanin-induced color changes

Smart films allow consumers to visually determine food freshness. We aimed to improve the surface contact area of gas permeation in anthocyanin (AH)-induced smart films by introducing nanocellulose (NC) prepared by sulfuric acid (CNSA), citric acid (CNCA), and TEMPO (CNF) to improve their sensitivity. The film matrix was composed of PVA . The structure, functionality, and sensitivity of films were compared. The results showed that films incorporating CNSA and CNCA had larger surface areas and stronger intermolecular interactions . Sensitivity tests showed a color change from blue-violet to yellow in PVA/AH-CNSA and -CNCA films at 131 ppm of ammonia, occurring within 4 min of exposure. Shrimp freshness was further monitored using the films, with three stages of shrimp freshness (fresh, sub-fresh, and spoiled) differentiated clearly via distinct color changes. A strong correlation between freshness indexes and color parameters was established. The PVA/AH-CNSA and -CNCA films are suitable for real-time monitoring seafood freshness.