Agglomeration Tendency during Top-Spray Fluidized Bed Coating with Gelatin and Starch Hydrolysate

Top-spray fluidized bed coating of glass beads with gelatin and starch hydrolysate leads to an `all or nothingʹ side-effect agglomeration, that is, a drastic collapse of the fluid-bed when a critical spray rate is exceeded. This undesirable side-effect agglomeration is primarily influenced by the type of coating, and more specifically its hygroscopicity, water binding capacity and viscosity. Hydrolyzed gelatin permits a considerable increase in spray rate compared to the unhydrolyzed type, due to more pronounced coating losses and lack of gelling capacity. Starch hydrolysate enables working only at low spray rates, due to its high hygroscopicity. Increasing the atomization pressure decreases the agglomeration tendency of starch hydrolysate but simultaneously decreases the final coating thickness. Coating quality is primarily influenced by coating properties, such as molecular mass and viscosity during processing.