Preparation Of Hollow Porous ZIF-8-based Nano Flavor And Study On Slow And Controlled Aroma Release

Essence is a liquid mixture with a special aroma.The microencapsulation of essence is the key to solve the problem of volatile and spoiled essence.The development direction of flavor microencapsulation must be to find better wall materials to achieve better sustained release,controlled release,intelligent response and other requirements.As one of the most widely studied MOF,ZIF-8 has the characteristics of mild preparation conditions and high hydrothermal stability.Taking ZIF-8 as a new wall material in the field of essence microcapsules is not only to find a new wall material for essence-flavor capsules,but also to apply ZIF-8 to new fields.(1)In this thesis,hollow porous ZIF-8 nanoparticles were prepared by soft template method,and then the hollow structure was used to adsorb cypress essential oil.On this basis,the wall materials,core materials and microcapsules were analyzed by infrared spectroscopy,scanning electron microscopy,transmission electron microscopy,XRD,Zeta potential,thermal stability,loading and p H controlled release.The obtained hollow porous ZIF-8 microcapsules have a particle size of about 40 nm and a loading amount of 17 wt.%.(2)Secondly,ZIF-8 cypress essential oil microcapsules were prepared by one-pot method of double emulsifier water-in-oil system for the first time.Firstly,the effects of emulsifier ratio,homogenization speed and homogenization time on the emulsion droplet size were investigated.Secondly,the effects of metal ions and organic ligands on the relative preparation results of oil phase and water and the state of microcapsules under different reaction time were investigated.On this basis,the particle size,micro-morphology and structure,functional groups,thermal stability and loading of the microcapsules were analyzed and tested.The microcapsules with a particle size of about 50 nm and a loading of cypress essential oil up to 22.7 wt.% were obtained.(3)Finally,in this thesis,a ZIF-8 cube was prepared with CTAB as a capping agent,with a particle size of about 155 nm,and the ZIF-8 was etched by proanthocyanidin for the first time to obtain a hollow proanthocyanidin cube cage.The materials were compared and characterized before and after modification.The cube cage is used to load cypress essential oil up to 26 wt.%.