A bio-based intelligent konjac glucomannan/carboxymethyl chitosan film with ZIF-67@carmine-enhanced freshness monitoring for seafood preservation

A multifunctional ZIF-67@Carmine (ZIF-67@Car) nanomaterial was synthesized and incorporated into a matrix of konjac glucomannan and carboxymethyl chitosan (KGM/CMCS, KC) to fabricate an intelligent active packaging film with dual functionality: active preservation and real-time freshness monitoring. Results indicated that KC remarkably enhanced the uniform distribution of ZIF-67@Car particle. Meanwhile, the addition of 20% ZIF-67@Car significantly improved the mechanical performance, hydrophobicity, and UV-blocking ability of the composite film. The optimized film demonstrated an ultimate tensile strength of 10.16 ± 1.05 Mpa and an elongation at break of 27.87 ± 3.53%. For active preservation, the film exhibited strong antioxidant activity (approximately 50% higher than pristine KC film) and potent antibacterial properties with over 99% inhibition rate. For intelligent monitoring, the film displayed a distinct colorimetric response to ammonia, transitioning from purple to brown during shrimp spoilage tests, enabling real-time visual freshness assessment. These findings confirm that the KC/ZIF-67@Car nanocomposite films, endowed with excellent antibacterial and ammonia-responsive functions, hold significant potential as intelligent active packaging materials for practical food preservation and quality assessment.