The soft microcapsules containing eucalyptus oil, ubiquinone and the fine water droplets could be prepared with interfacial dehydration reaction between hydroxy methyl cellulose and tannic acid using the water-in-oil-in-water type multiple (W/O)/W emulsion. The diameters of the microcapsules and the content and the microencapsulation efficiency of the core materials were significantly affected by the revolution velocity (Nr1) to form the (W/O) emulsion and the revolution velocity (Nr2) to form the (W/O)/W emulsion and the lecithin concentration. The mean diameters of the inner water droplets and those of the microcapsules were proportional to Nr1-1.25 and Nr1-0.11 for the revolution velocity (Nr1), respectively. With increasing the revolution velocity (Nr1), the content and the microencapsulation efficiency of the inner water droplets increased, while those of the oil phase decreased. The mean diameters of the microcapsules were proportional to Nr2-1.1. The content and the microencapsulation efficiency of the inner water droplets and those of the oil phase decreased with the revolution velocity (Nr1) and increased with the lecithin concentration.
Keywords: Soft microcapsule; eucalyptus oil; interfacial dehydration reaction; multiple emulsion; physiological active substance; ubiquinone.