| Essential oil, the plant secondary metabolites, has the function of flavouring raw materials, anti-inflammatory, antiseptic, antioxidant and promoting cell regeneration. Therefore, the essential oil has been widely applied in food spices, cosmetics, pharmaceutical engineering, agricultural pest control and other fields. However, the essential oil is volatile, poor water-solubility and chemically unstable in the presence of air, light and high temperature, which can obviously limit its practical application. The problem about the application of the essential oil is solved commendably by the microcapsule technology, which greatly expand the development of the essential oil industry.This thesis is mainly divided into three parts, the quaternary ammonium salt of chitosan(HACC)/sodium alginate(SA) microcapsules containing different essential oil were prepared by complex coacervation, spray drying and Pickering emulsion templating. And the performance was characterized at the same time. The main content of this paper is as follows:(1) In this study, flavour tea tree oil(TTO)-loaded antibacterial microcapsules were developed basing on complex coacervation of sodium alginate(SA) and quaternary ammonium salt of chitosan(HACC). The optimum preparation condition of the TTO-loaded microcapsules determined by response surface methodology(RSM) was as follows: the weight ratio of core to wall material(core-wall ratio) of 1:1, the p H value of 6.0 and the mass concentration of Ca Cl2 solution of 0.6 w/v%, at which the resultant microcapsules showed the greatest actual encapsulation efficiency(EE) of 66.06%±2.53%. Thereafter, the resultant microcapsules were characterized in terms of morphology, size, component and thermal stability by scanning electronic microscope(SEM), laser particle diameter analyzer(LPDA), Fourier transform infrared spectroscopy(FTIR), thermal gravity-differential thermal analysis(TG-DTA) and differential scanning calorimeter(DSC), respectively. Furthermore, both in vitro drug release and antimicrobial properties of the microcapsules were also assessed. The results displayed that the TTO-loaded microcapsules had a spherical shape with the particle sizes in the range from 1.91 ?m to 13.18 ?m. The microcapsules possessed outstanding performances in the thermal stability, sustained release activity, antimicrobial effect and long-term inhibition activity. The release profiles of TTO from the microcapsules could be well described by the Rigter-Peppas model. Based on the above research results, the simple and environmentally-friendly microencapsulation formulation could effectively improve the stability performance and prolong the antimicrobial efficacy of TTO. The microcapsules may find applications in food, cosmetics and medicine fields.(2) In this work, the sodium alginate- N-2-hydroxypropyl trimethyl ammonium chloride chitosan(HACC) microcapsules containing cinnamon oil were prepared by spray drying method. The wall material ratio, ratio of core wall and the concentration of emulsifier had been investigated for the encapsulation efficiency(EE) of the microcapsules via single-factor experiment, and the best preparation technology of spray drying was discussed. As a result, the optimum condition for microcapsules preparation was:(i) emulsification speed=3000 rpm;(ii) the amount of surfactants=1%;(iii) wHACC:wALG=2:1;(iv) core-shell ratio=1:1(w/w);(v) compressed air volume=70%;(vi) spraying pressure=0.4 Mpa;(vii) inlet temperature=120 °C. The EE of the microcapsules were 77.38%. Meanwhile, SEM, FT-IR and TGA were performed to characterize the particle size distribution, the chemical structure and the thermal stability. The result showed that the microcapsules were with a spherical shape with average particle size of 2.36 ?m. Besides, the release and antibacterial properties were also investigated. The release of the cinnamon oil from the microcapsules obeyed the free diffusion mechanism of Fickian. The minimal inhibitory concentrations(MICs) of the microcapsules against Staphylococcus aureus and Escherichia coli were both 0.312 mg/m L. This preparation process is simple, continuity and effective, which is helpful for realizing industrial production. There has a great reference for the development of microcapsule technology in the food, pharmacy and pesticide industry.(3) Citronella oil(CO)-loaded microcapsules with hydroxyapatite(HAp)/HACC/SA shells were facilely prepared by oil-in-water(O/W) Pickering emulsion templating. CO-in-water emulsions were stabilized using HAp nanoparticles as the particulate emulsifier. The hybrid shells were fabricated by the electrostatic adsorption of HACC and SA. The Oil/water ratio, p H and the concentration of HAp was studied for the influence of pickering emulsion. And the CO-loaded microcapsules were prepared by this Pickering emulsion as templating. SEM showed that the microcapsules were a spherical shape with average particle size of 13.638 ?m. And the vitro release of microcapsules under different the Oil/water ratio and the concentration of HAp also evaluated. The result showed the release of the CO from the microcapsules revealed the rapid release of the initial stage and then the stage of slow release, which was followed Rigter-Peppas model. Moreover, the antimicrobial activity were also evaluated by the disc diffusion method and minimum inhibitory concentration, showing the antibacterial effect against Staphylococcus aureus and Escherichia coli of CO- loaded microcapsules were better than hollow microcapsules. The microcapsules can be applied in medicine as a drug release system, textile industry as an antibacterial agent, perfumery industry as a fixative. |
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