Spray Drying of Suspensions for Pharma and Bio Products: Drying Kinetics and Morphology

An experimental investigation of the spray drying behavior of droplets containing excipients and carrier materials used in the pharmaceutical and biotechnological industries has been conducted. Specifically, rice starch suspensions with different amounts of TiO2, maltodextrin, dextrin, NaCl and Na2SO4 are dried.

The drying rate is measured, and the morphology formation is mapped to obtain a more fundamental understanding of the drying process, which is very useful when designing product formulations. In the pilot spray dryer, droplet generation is based on the JetCutter technology and the droplets are dried under well-defined temperature and flow conditions.

The droplets are sampled during drying to determine the drying rate, and the dried particles are collected for morphology analysis. The results show that reducing the water activity in a suspension of insolubles by adding various amounts of inorganic salts or carbohydrates causes an increase in the droplet temperature during spray drying resulting in a rather constant the drying rate.

Further, the results show that small alterations in the droplet composition may significantly change the final particle morphology. The observed morphologies are discussed in detail.