Micronization of the natural pigment-bixin by the SEDS process through prefilming atomization

Bixin was micronized from dichloromethane solution using Supercritical CO2 (SC-CO2) as antisolvent by the SEDS process through Prefilming Atomization (SEDS–PA) with the aim of evaluating the efficiency of the supercritical fluid precipitation technologies in processing natural pigments and studying the effects of operating variables in the SEDS–PA process. Morphologies and sizes of microparticles were analyzed using scanning electron microscopy. This study has shown that the sizes of the bixin microparticles could be substantially reduced by the SEDS–PA process. The precipitates obtained at all experimental conditions were needle-like or coalesced net-like particles. With the increase of SC-CO2 flow rate the impingement of SC-CO2 on the liquid film and the consequent mixing of SC-CO2 and droplets are reinforced, producing smaller particles. For constant SC-CO2 flow rate, with the increase of solution flow rate the impingement of SC-CO2 on the liquid film becomes weak leading to formation of bigger particles. Higher solution concentration results in formation of bigger particles and increase of agglomeration. Sizes of bixin microparticles decrease with pressure. Serious agglomeration and coalescence phenomena at the high operating temperature result in precipitation of net-like products.