Synthesis of Water Stable γ‐Cyclodextrin Metal–Organic Frameworks as a Carbon Dioxide‐Selective Layer for Preservation of Fresh‐Cut Pears by Modified Atmosphere Packaging

Modified atmosphere packaging (MAP) is widely used in the preservation of fruit, but CO2 concentration in most MAP continues to increase because of the respiration of fruit, which causes CO2 injury to fruit. Herein, a three-layer composite film is prepared by using a layer-by-layer stacking method, with diphenyl carbonate crosslinked cyclodextrin metal-organic framework (DPC-CL-CD-MOF) as the inner layer, polycaprolactone nanofiber film as the middle layer, and chitosan casting film as the outer layer. Among three layers, the DPC-CL-CD-MOF layer can increase the CO2 permeability and CO2/O2 selectivity of the composite film because of its CO2 adsorption capacity. The film exhibits moderate thermal stability but lacks mechanical strength. Gas permeability tests show that with increasing DPC-CL-CD-MOF loading content from 5% to 15%, the CO2 permeability coefficient decreases of the film from 2002.16 to 582.69 barrer. The CO2/O2 selectivity peaks at 19.12 with 10% DPC-CL-CD-MOF. When applied in preserving fresh-cut pears under active MAP conditions (5% O2, 10% CO2), the three-layer composite film with 10% DPC-CL-CD-MOF effectively prevents fresh-cut pears from CO2 injury, inhibiting browning and softening of pears, reducing polyphenol oxidase activity, malondialdehyde content, and hydrogen peroxide content of fresh-cut pears.