Supercritical carbon dioxide : an efficient tool for the production of ultra-fine particles for the food and pharmaceutical industries
Résumé
The agro-food, pharmaceutical, cosmetics and detergent industries are among the greatest users of particulate solids, or powders. It is hardly necessary, therefore, to expound their industrial importance. However, there is still plenty of room for development, as their generation, their formulation and the control of their usage properties are yet to be fully mastered.
In the domain of particle formation, there are traditionally two main ways of obtaining divided solids, depending on whether the base material is in the solid or liquid state: crushing, milling, comminution belong to the former category while crystallisation, precipitation, spray-drying and atomization belong to the latter.
Obtaining powders by processes using supercritical fluids is a third route, which has undergone significant development during the last decade. By using pressure as an operating parameter, these processes lead to the production of fine and monodisperse powders. There exist three families of processes (RESS, SAS and PGSS) according to the way in which the FSC - generally CO2 - is used.
•In the RESS process, CO2 is the solvent and it is the fall of density related to a rapid depressurisation which promotes the nucleation of the solute. Although it is easy to implement, this process is however limited by the relatively tight spectrum of CO2-solvent properties.
•In the SAS process, CO2 is used as a non (or anti)-solvent and it is the reciprocal dissolution of an organic solution and the supercritical fluid which causes precipitation. The great versatility of SAS remains its principal advantage.
•Lastly, in the PGSS process, the dissolution of CO2 into an organic solution or a molten polymer, is followed by an abrupt depressurisation in which the dissolved gas acts as an aerosol generator helping the particle formation. This process is particularly advisable for polymer coating applications.
In this paper, two examples of application of these processes are described.
A high-value foodstuff, cocoa butter has been crystallised in a specific polymorph. The particles produced can be used to improve tempering, a key-stage in the chocolate manufacturing process.
Secondly, a hypocholesterolemic drug, eflucimibe, has been processed. A new process using three different steps has allowed a significant improvement in dissolution rate and oral bioavailability.
Origine : Fichiers produits par l'(les) auteur(s)
Loading...