Upcycling grapefruit peel pectin, curcumin, and Zn-CD into a high-performance biodegradable film for meat preservation and colorimetric freshness tracking.

To mitigate meat spoilage and plastic pollution, a multifunctional intelligent/active packaging film was developed using pectin extracted from grapefruit peel as the film matrix, combined with grapefruit peel residue-derived Zn-doped carbon dots (Zn-CD) and curcumin. Zn-CD and curcumin synergistically altered the microstructure of the pectin film, significantly enhancing its mechanical strength, UV-blocking performance, water/oxygen barrier properties, and antioxidant/antibacterial activities. The PC-5%CE-CD film exhibited sensitive pH/ammonia-responsive color changes from yellow to reddish-brown, enabling real-time visual monitoring of pork freshness with a strong correlation between color change and TVB-N accumulation. Moreover, the film effectively inhibited microbial growth, reduced protein degradation, and extended the shelf life of chilled pork, outperforming pure pectin controls. In addition, compared with polyethylene film, the PC-5%CE-CD film was easily degradable in soil. Therefore, the PC-5%CE-CD composite can serve as a promising multifunctional and environmentally friendly sustainable food packaging material for intelligent active packaging applications.