Study On The Preparation And Properties Of Oregano Essential Oil Microcapsules

Oregano, a natural medicinal and edible plant, can be used as medicinal material. Oregano essential oil is extracted from the whole plant, having the desired effect in terms of antibiosis and anti-oxidation and so on, moreover, its superiority of natural, green, efficient and non-toxic make it have broad application prospects. However, the disadvantages of its high volatility, poor stability, not easy storage and transportatio are the problems that limit its application to a certain extent. This paper selects three materials, including ?-cyclodextrin, gelatin/gum arabic, chitosan/gum arabic as wall materials to embed oregano essential oil using microencapsulation technology. The processing and conditions of microencapsulation were optimized and their related performances were also tested. The main results are as follows:(1) The microcapsule of oregano essential oil was repared using saturated water solution method which chooses ?-cyclodextrin as wall material, and it was a white powdery solid with an average particle size of 5 ?m. The antibacterial tests on E. coli strains showed that oregano oil microencapsulated still has a significant inhibitory effect, and its result on Aspergillus oryzae strains showed that oregano essential oil microencapsuled result in more lasting antibacterial effect, compared with the oil itself.(2) Selecting gelatin/gum arabic as wall materials oregano oil microcapsules are prepared through complex coacervation methods. Choosing embedding rate as the main indicator, the optimum processing conditions were made by a single factor and orthogonal experiments, and the results are as follows: the ratio of core and wall is 3: 1, the dosage of emulsifier WJE-880 0.1%, emulsification rate 6000 r/min, reaction pH 4.5, and solidifying process is to control the speed of 250 r/min for 60 min in a water bath at 55 ?. Under these conditions the corresponding microcapsules, a kind of reddish spherical particle, were prepared and the embedding rate can reached to 83.1%. The tests of antibacterial activity on Escherichia coli, Staphylococcus aureus, Botrytis cinerea, Tomato early Phytophthora showed that oregano essential oil has better antibacterial effects after microencapsulation, especially in its longer effects.(3) With complex coacervation method and choosing chitosan/gum arabic as wall materials, the best technological conditions for the oregano essential oil microcapsules can be concluded as following: the concentration of acetic acid to dissolve the chitosan is 1.5%, the ratio of core and wall 3.5: 1, reaction pH 9.0 and the water bath temperature 40 ?, according to the above conditions, the microcapsules are pale yellow spherical particles, with an average particle size of 100 nm and the embedding rate can reach to 81.8%.(4) The thermoqravimetric analysis on oregano essential oil microcapsule showed that the thermal stability of oregano essential oil has been greatly improved after microencapsulation with all three materials especially by the material: gelatin/gum arabic, which is also the best material in the three materials.After microencapsulation oregano essential oil is changed, on the one hand, from a liquid into a solid material, easy to transport, covering its pungent and unpleasant odor. On the other hand, oregano essential oil microencapsulated still has lasting antibacterial activity and greatly improve the thermal stability. Above changes make the oil has broader prospect for application.