Design And Application Of New Functional Materials For Preservation Packaging Of Fruits And Vegetables

Preservation of fruits and vegetables is very important for the storage and sale of fruits and vegetables after postharvest.Adopting scientific preservation technology can effectively extend the storage period of fresh fruits and vegetables,and maintain the value of fruits and vegetables.Facing the two significant problems of continued active physiological metabolism and microbial pollution after postharvest,researchers have developed and used a variety of physical,chemical and biological preservation methods.In this thesis,we used catalysts and natural antibacterial agents,combined with nanofibers and porous materials,to achieve the purpose of degrading ethylene and inhibiting microbial growth.The main contents are as follows:1.Polyacrylonitrile nanofibers were prepared by electrospinning.TiO2 nanoparticles were developed by the hydrolysis method,which was attached to the surface of polyacrylonitrile nanofibers.Then,PAN@TiO2 composite nanofibers with a core-shell structure were obtained.The catalytic performance of the composite nanofibers was tested by photocatalytic degradation of ethylene.The results showed that the synthesized TiO2 nanoparticles were uniformly dispersed on the surface of the polyacrylonitrile nanofibers and had excellent catalytic activity.The maturation experiments of green tomatoes proved that the composite nanofibers could effectively degrade ethylene and be used for the preservation of ethylene-sensitive fruits and vegetables.2.Nitrogen-doped titanium dioxide(N-TiO2)nanoparticles were synthesized by solvothermal method.Under high environment relative humidity,PCL/N-TiO2 composite porous fibers were prepared by using PCL as the carrier of N-TiO2.The results showed that the synthesized composite porous fibers had a certain photocatalytic activity under visible light.The maturation experiments with green tomatoes had verified that the composite porous fibers had a certain effect of degrading ethylene under visible light irradiation.3.Zirconium-based metal-organic frameworks(Zr-MOF)with two different organic ligands,UiO-66-NH2 and UiO-66-(OH)2,were synthesized by the solvothermal method and heating reflux method,respectively.They were used as carriers of thymol to adsorb thymol essential oil.The release rate of thymol adsorbed by two kinds of Zr-MOF was determined by the UV spectrum,which showed that UiO-66-NH2 had a better sustained release effect on thymol.Antibacterial experiments and strawberry preservation experiments showed that thymol had excellent antibacterial properties.Therefore,UiO-66-NH2 could be used as a carrier of sustained-release thymol to apply to the preservation of fruits and vegetables indirectly and inhibit the reproduction of microorganisms.