Micronization Of The Chitosan Blended With Essence By A Supercritical Fluid Assisted Atomization Process

Recently, with the advantages of mild operating conditions and controllable particles' sizes and morphologies, the supercritical fluid(SCF) technology which has widely used in functional material micronization has developed rapidly. In such many SCF processes, One promising process is the supercritical fluid assisted atomization(SAA) which is developed from the SAS process and can produce smaller and more narrowed size distribution particles. Moreover, the fact that it can produce fat-soluble and water-soluble particles makes up the shortages of RESS and SAS process.This work discussed the development and procedure of SAA process and studied the micronization of the chitosan blended with essence by SAA process. Two styles of particles[solid-liquid and solid-solid styles in which chitosan was carrier and vanillin(solid) and lavender essential oil(liquid) were the main essences] were studied. There were several operating conditions making effect on the particle size, size distribution and particle adhesion. These operating conditions, such as the precipitator temperature, the materials ratio, the pre-expansion pressure, the pre-expansion temperature and the flow rate of the solution, were investigated. The particle morphology was observed by SEM and statistics of particle data were deduced from the SEM images. The odor emitted by the particles was characterized by gas chromatography.Results showed that the average particle size decreased with the decrease of the materials ratios as well as the pre-expansion temperature and the increase of the pre-expansion pressure as well as the flow rate of the solution. The factors which affect the size distribution and particle adhesion of two systems were different:the chitosan/lavender particles' size distribution got more concentrated and the adhesion of particles became of lower degree by declining the ratios and temperature. However, the size distribution became more distributed before be more concentrated as the increase of pre-expansion pressure and solution flow rate. The more concentrated particles' adhesion were also of lower degree. The chitosan/vanillin particles'size distribution became concentrated with the decrease of the materials ratios as well as the pre-expansion temperature and the increase of the pre-expansion pressure as well as the flow rate of the solution. But the particles became more adhesive with overlow material ratios and exorbitant solution flow rates.Particles obtained by the SAA process were spherical in morphology. With the operating conditions of the chitosan/lavender ratio 0.8/1, the pre-expansion temperature 50℃, the pre-expansion pressure 10.5Mpa and the solution flow rate 1.5mL/min, the mean diameter of the chitosan/lavender particles was 2.2μm. With the operating conditions of the chitosan/lavender ratio 0.8/1, the pre-expansion temperature 50℃, the pre-expansion pressure 10.5Mpa and the solution flow rate 1.5mL/min, the mean diameter of the chitosan/vanillin particles was 2.0μm. The interior of both particles was benefit for the slow-release of the aromatic materials. The images obtained from the GC showed that the odor of chitosan/ lavender essential oil particles lasted over 5 months with the constituents integrated. The odor of chitosan/vanillin lasted only 4 months.