Study On Complex Coacervation Microencapsulation Of Glutathione

Complex Coacervation microencapsulation is a reaction use two polymer material materials with opposite charges as wall material, and scattered core material in wall solution. By changing the conditions(such as p H and temperature), the coacervation of poly material was driven by electrostatic interactions. After the reaction, the solubility of polymer materials decrease and the phase separation led to the formation of microcapsule. As the reaction conditions of complex coacervation is mild, and it has very high payloads, there are many research about complex coacervation microencapsulation.Complex coacervation is typically used to encapsulate hydrophobic material to prevent the reaction between core material and wall material, but little progress has been reported on encapsulation of hydrophilic substances. In this paper, the microencapsulation of hydrophilic peptides was investigated, glutathione microcapsules were prepared using gelatin and gum arabic as wall materials by complex coacervation and the core material was the W/O emulsion of glutathione(GSH) solution. The effect of various processing parameters was investigated: the physical and chemical properties of GSH microcapsules were researched; the stability of GSH and microcapsule products in high temperature conditions, under simulated gastrointestinal conditions and storage conditions was examined to prove the protection of the microcapsules for GSH. The results provide a theoretical basis for application of GSH microcapsules in the food processing or storage, and expand the complex coacervation microcapsule technology in embedding water soluble protein or functional peptides.With the stability of the core material as indicator the core material emulsion optimum formula and technological conditions was investigated. When soy lecithin was chosen as emulsifier during the preparation of microcapsules, the optimal material formula was 15%(w/w) GSH solution, 50%(w/w) water/oil ratio with 3%(w/w) lecithin in W/O emulsion, the emulsification rate was 12, 000 r/min and the emulsification time was 4 min. The observation of fluorescent showed that the core material emulsion could keep stable in the preparation of microcapsule. And the preparation conditions of microcapsules was 1:1 core/wall ratio, 1%(w/v) wall material concentration, stirring speed 400 r/min. The yield and efficiency of GSH microcapsules was around 90%, the embedding rate was around 85%, the morphology observed by a microscope was spherical and uniform, the average particle size was 15 μm.Physical and chemical properties of GSH microcapsules dried by spray drying and freeze drying were compared. By measuring the moisture, density and the repose angle, we got the conclusion that the microcapsules had low moisture which was fitted to store, and the fluid was good. Scanning electron microscope observation results showed that microcapsule was good integral and compact. FTIR con?rmed that the coacervation between the wall materials was electrostatic reaction. The glass transition temperature(Tg) of the microcapsules was 57.75 °C, which was higher than the usual storage temperature(25 °C), so the product could be stored at room temperature in the glassy state. The thermogravimetric analysis(TGA) result showed that the wall materials has good stability at high temperature.The storage experiment of microcapsules and GSH in 80 °C hot water and 150 °C oven for 2 h showed that the wall of microcapsules could protect GSH from high temperature. The stability of microcapsule in simulated digestion mainly associated with p H and enzymes, the results showed that the addition of salivary amylase had no effect on the stability, but pepsin caused a slow release of core material, and trypsin degraded microcapsules quickly in 1 h, then led to the release of core material. The higher levels of p H also reduced the stability of the microcapsules.The study of storage conditions mainly included light, temperature and relative humidity on the stability. Compared with the dark storage, the retention rate under the condition of light was lower, but the retention rate of microcapsules was significantly higher than the free GSH. The microcapsules under the condition of 4 °C, 25 °C was stable, and the stability was decreased in 40 °C. Microcapsules were relatively stable under the condition of low humidity storage(relative humidity 33% and 58%), when relative humidity rose to 80%, the stability of the microcapsules decreased. This indicated that the illumination, temperature and relative humidity had a significant influence on the storage stability of the microcapsules.