Water-resistant CMC/g-C₃N₄ based multifunctional film for high-humidity fruit packaging

This study focused on developing a carboxymethyl cellulose (CMC)-based packaging film with excellent water resistance for preserving high-moisture foods. To this end, we incorporated exfoliated graphitic carbon nitride (g-C₃N₄) into a CMC matrix and cross-linked it with citric acid (CA) and carbon dots (CD) to create a multifunctional, nacre-mimicking double-cross-linked film (CMC/g-C₃N₄/CA/CD). The CMC/g-C₃N₄/CA/CD film showed a 58.8% increase in tensile strength and a 40.0% reduction in water vapor transmission rate compared to the control CMC film. Additionally, its moisture resistance improved significantly, and it kept its shape intact even after being immersed in water for 100 h. Moreover, the composite film demonstrated excellent functional properties, including a strong antioxidant effect that completely removed ABTS radicals and a potent antibacterial effect that fully inhibited the growth of S. enterica and L. monocytogenes. When used for blueberry packaging, this film effectively inhibits microbial contamination, maintains pH and firmness, reduces weight loss, and extends shelf life by up to 16 days. This nacre-mimicking biopolymer-based packaging material, with its high moisture resistance and physical strength, offers a promising alternative to petroleum-based plastic packaging.