Effects of extraction temperature, extraction pressure and nozzle diameter on micronization of cholesterol by RESS process

Micronized cholesterol particles were produced via the Rapid Expansion of Supercritical CO₂ Solutions (RESS) process. Taguchi design was used for designing the experimental plan to investigate the effects of three parameters including extraction temperature (40-60 °C), extraction pressure (100-160 bar) and nozzle diameter (0.15-0.24 mm) on the size and morphology of the cholesterol particles produced by the RESS process. The characterization of the particles was carried out using scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements to evaluate the performance of RESS process. The average particle size of the original material was 55 μm ± (2.84) while the average particle size of cholesterol after size reduction via the RESS process was between the minimum of 0.62 μm ± (0.03) and the maximum of 4.83 μm ± (0.18) depending upon the experimental conditions used. It was observed that both increasing the temperature from 40 to 60 °C and increasing the nozzle diameter from 0.15 to 0.24 mm result a reducing effect on the average particle size, whereas extraction pressure (100-160 bar) change has slight effect on the average particle size.