Pectinase-responsive UiO-66-COOH/pectin coating system for targeted release of potassium cinnamate: A novel strategy for smart fruit preservation

This study integrates UiO-66-COOH metal–organic frameworks (MOFs) with pectin (Pec) to precisely release potassium cinnamate (PC) to develop a pectinase-responsive active fruit-preservation system (UiO-66-COOH@PC/Pec). Carboxylated UiO-66 with nanoporosity was fabricated to achieve a high loading amount of PC (235 mg·g −1 ) via the synergistic effects of hydrogen bonding, as shown by the loading kinetics and reduced density gradient analyses. A gatekeeper was established by grafting Pec onto the surface of the MOF (UiO-66-COOH@PC/Pec), thereby “locking” PC to prevent leakage. Moreover, an enzyme-responsive controlled-release behavior was developed under pectinase stimulation, achieving up to 95 % PC release within 9 h through Fickian diffusion and only 25.3 % in enzyme-free conditions by non-Fickian diffusion and matrix erosion. With significant long-term inhibiting activity against both bacteria and fungi, UiO-66-COOH@PC/Pec successfully extended the shelf life of strawberries from 2 to 5 days at 25 °C. Moreover, UiO-66-COOH@PC/Pec exhibited good water solubility and negligible toxicity, indicating that it can be easily removed from fruit surfaces and offers high consumer acceptance. These results provide a novel MOF-based controlled-release strategy for smart food-packaging applications.