Biosafe Cu-MOF loaded chitosan/gelatin-based multifunctional packaging film for monitoring shrimp freshness

As living standards improve, the demand for food freshness has gradually increased. Multifunctional packaging materials that monitor food freshness in real-time, delay spoilage, and are environmentally friendly have emerged as ideal solutions. This study synthesized an ammonia-sensitive copper-based metal-organic framework (Cu-MOF) and incorporated it into a matrix composed of chitosan (CS) and gelatin (Gel). The resulting film exhibits ammonia-sensitive color-changing properties, antibacterial activity, and excellent biodegradability. The effects of Cu-MOF incorporation on the structural, physical, and functional properties of the CS/Gel films were systematically evaluated. Results demonstrated that the Cu-MOF was uniformly distributed within the CS/Gel matrix, significantly enhancing the mechanical properties (tensile strength increased by 68.49%), oxygen/water vapor barrier properties, and UV-blocking capability of the films. Notably, the CS/Gel@Cu-MOF films exhibited excellent antibacterial performance, with sterilization rates of 94.2% against Escherichia coli and 99.6% against Staphylococcus aureus. Additionally, the films showed good biocompatibility, biodegradability, and a sensitive color response to ammonia. The films were successfully used to monitor shrimp freshness through color change, transitioning from light green to brown as spoilage occurred. These findings indicate that CS/Gel@Cu-MOF films have significant potential for real-time visual freshness monitoring in food packaging, contributing to reduced food safety risks and waste.