Advanced chitosan hybrid dye labels for dynamic monitoring of shrimp and milk freshness

Abstract

This study presents the development of intelligent screen-printed labels for real-time food freshness monitoring. Using chitosan grafted with rosolic acid (RA) and immobilized on montmorillonite (MMT) through cationic exchange, a hybrid dye was synthesized and applied in screen-printing inks. The hybrid structure was characterized by XRD, TGA, and UV–vis, confirming improved thermal stability and maintained halochromic properties. SEM analysis showed consistent ink deposition on filter paper, while water contact angle (WCA) measurements demonstrated enhanced surface hydrophobicity due to the MMT. The labels exhibited clear pH-sensitive color transitions from yellow to purplish red (pH 2.0–12.0) and rapid ammonia sensitivity, with ΔE values exceeding 45.0 within 10 min. The labels also demonstrated excellent reversibility, storage stability, leaching resistance, and cytocompatibility. Practical tests on shrimp and milk confirmed the labels' ability to accurately monitor freshness through visible color changes. These findings highlight the potential of hybrid labels as effective, scalable freshness indicators for intelligent food packaging.