Bamboo cellulose nanofiber-based smart colorimetric films for shrimp freshness monitoring

Cellulose nanofiber (CNF) with an average diameter of 35.67 ± 0.23 nm was prepared from bamboo processing waste through a combination of enzyme-assisted ball milling and high-pressure homogenization. After modification with maleic anhydride (MA), neutral red (NR) was adsorbed onto the CNF-MA, and the resulting CNF-MA-NR films were prepared by vacuum filtration. The CNF-MA-NR film exhibited efficient NR immobilization, improved hydrophilicity, and satisfactory biocompatibility. The immobilized NR retained pH-responsive behavior with a broadened color transition range and showed rapid, reversible response to amine and acid vapors, along with good reusability. The films were biodegradable and showed stable color performance under low-temperature and dark storage without NR leakage. Correlation analysis using refrigerated shrimp confirmed that the film enabled real-time monitoring of shrimp freshness via a WeChat Mini Program. This work provided a sustainable approach for valorizing bamboo processing waste and demonstrates the potential of CNF in colorimetric sensing.