Microcapsultion Of Peppermint Oil By Coacervation

Microencapsulation by coacervation is the phase separation of one or many hydrocolloids from the initial solution and the subsequent deposition of the newly formed coacervate phase around the active ingredient suspended or emulsified in the same reaction media. After hardened, the wall of microcapsules forms web structure, so microcapsules by coacrvation possesse excellent heat- and moisture-resistant properties and controlled release property.The preparation method of spherical multinuclear microcapsules by coacervation was investigated. The cross-linking parameters in the process of transglutaminase-hardened microcapsules by coacervation were optimized. The release kinetics and the storage stability of microcapsules by coacervation were also explored. The composition and properties of coacervate as wall material were investigated, accordingly explaining why some processing parameters affect on the the particle size and morphology and heat-resistant properties. Finally the spherical multinuclear microcapsules by coacervation were applied in biscuit and tabbco, obtaing good applicable effectiveness.The gelatin/gum arabic multinuclear microcapsules encapsulating peppermint oil were prepared by coacervation. The yield of microcapsules by coacervation was about 90%. The effect of the core/wall ratio, pH, the stirring speed, the gelatin/gum arabic ratio on loading was very significant. The optimal conditions for preparing spherical multinuclear microcapsules by coacervation were as follows: wall material concentration 1%, core/wall ratio 2:1, gelatin/gum arabic ratio 1:1, pH 3.7 and stirring speed 400 rpm.With the increase of the hardening time, TG concentration and the hardening temperature, the hardening effectiveness of microcapsules by coacervation was significantly improved. At the pH 6.0 the hardening effectiveness of microcapsules by coacervation was best, but when the hardening pH deviated from 6.0 the hardening effectiveness turned poor. Compared with formaldehyde, transglutaminase exhibited similar microcapsule hardening effectiveness. The optimum hardening parameters obtained by the orthogonal experiment were as follows: pH 6, hardening for 12 h at 15℃and TG concentration of 7.5U TG/g gelatin.In hot water and heating air, the coacervation microcapsules followed first order release kinetics and zero order release kinetics respectively. The release kinetics rate constant increased with the core/wall ratio. The effect of pH and the concentration of microcapsules suspension on the storage stability was small. The microcapsules of the core/wall ratio of 1:1 and 1:2 had better storage stability.The effect of pH on the composition of coacervate was very significant. With the decrease of pH, the convention of gelatin firstly increased, subsequently decreased. The convention of gum arabic remained constant at the beginning, then increased with the decrease of pH. When the pH decreased, the total zeta potential of gelatin and gum arabic turned from negative to positive. According to the effect of pH on the convention and zeta potential of gelatin and gum arabic, the modal of coacervate produced through the interaction of gelatin and gum arabic was obtained.The effect of pH on the thixotropy property of coacervate was very significant. At pH 3.7, the thixotropy property and gel property of coacervate obviously increased. With the increase of pH and ratio of gelatin/gum arabic, the thixotropy property of coacervate decreased, however, the gel property increased.FT-IR spectrum proved that the coacervate was formed by the physical interaction between gelatin and gum arabic, not chemical interaction. After hardened by TG, the content of gum arabic in the coacervate decreased and the chemical bond among gelatin molecules was formed. At pH 4.0 and the ratio of gelatin/gum arabic 1:1, the microcapsules possessed spherical morphology and undulate surface, but there weren't cracks and small holes. At other conditions, the surface of microcapsules possessed undulate surface, cracks and small holes.During the preparation of microcapsules by coacervation, the loss of the micro-components such asα-pinene, was more significant than the macro-components, such as menthol and menthone. But through double encapsulation, the loss of micro-components decreased. Considering the biscuits withβ-CD, coacervation micocapsules and microcapsules by double encapsulation respectively, the sensory evaluation indicated that these biscuits had similar mint flavor intensity which was higher than biscuits with not-encapsulated mint oil. The acceptance of biscuit containing micocapsules by double encapsulation was higher than the biscuit containing coacervation microcapsules, so the microcapsules by double encapsulation exhibited better application effectiveness.Considering the tobacco with not-encapsulated mint oil, the loss of peppermint oil was so big after drying that some micro-component, such asα-pinene, had disappeared completely. However, the loss of peppermint oil in the tobacco containing microcapsules by double encapsulation decreased significantly after drying and the micro-components were protected very well during drying. The loss of peppermint oil was greater in the middle-scale experiment, but the sensory evaluation indicated that the tobacco with microcapsules by double encapsulation still possessed good sensory effectiveness after drying in middle-scale experiment.