Abstract
It was tried to develop the preparation method for microencapsulating the uycalyptus oil containing fine aqueous droplets by using the interfacial condensation reaction between hydroxyl propyl methyl cellulose and tannic acid. Uycalyptus oil containing fine aqueous droplets was dispersed in the continuous water phase to form the (W/O)/W emulsion. Tannic acid and hydroxyl propyl methyl cellulose were dissolved in the inner aqueous droplets and in the outer continuous water phase, respectively. Tannic acid transferred through the oil phase from the inner water droplets to the interface between the oil phase and the continuous water phase and then, reacted with hydroxyl propyl methyl cellulose. In the experiment, the concentrations of hydroxyl propyl methyl cellulose and tannic acid were mainly changed stepwise. The uycalyptus oil containing the fine water droplets could be microencapsulated satisfactorily. It was found that the microcapsules were composed of the gelated hydroxyl propyl methyl cellulose film as the shell, the fine aqueous droplets as the first core and the oil droplet as the second core.
Highlights
Many kinds of microcapsules have been developed and applied to the various fields such as cosmetics, paintings, catalyst, food industry, medicine, agriculture, and so on [1]-[3].The purposes of microencapsulation are to optionally release the core material, to protect the core materials from environment, to modify the surface of core material, to mask the taste of core material and so on
On the other hand, when the concentrations of Hydroxy propyl methyl cellulose (HPMC) and Tannic acid (TA) were higher (CHPMC = 0.2 wt%, CTA = 0.06 mol), the TA aqueous droplet was kept on the interface for ca. 10 min as shown in Figure 4(b) due to the thicker film formation
It is found that the film was not formed at CTA = 0 in spite of elapsing of ca. 30 s and the gelated film was formed above the concentrations of CHPMC = 0.05 wt% and CTA = 0.01 mol
Summary
Many kinds of microcapsules have been developed and applied to the various fields such as cosmetics, paintings, catalyst, food industry, medicine, agriculture, and so on [1]-[3]. Many kinds of oil species have been microencapsulated with the chemical methods such as interfacial gelling reaction method [11]-[13], the in-situ polymerization [14] [15], the interfacial polycondensation reaction [16] [17] and the physicochemical methods such as the coacervation method [18] [19], the spray-dried method [20]-[22], and the melting dispersion-cooling method [23] In these preparation methods, a few harmful chemical species have been used and the complicated processes have been applied. The purposes of this paper are to develop the microencapsulation procedure with the interfacial condensation reaction between hydroxyl propyl methyl cellulose and tannic acid, to investigate whether the microcapsules of uycalyptus oil containing the fine water droplets can be prepared or not, to characterize the microcapsules and to discuss the microencapsulation mechanism on the basis of the results obtained
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