Effect of Starch Paste Concentration on Particle Size Distribution of Fine Granules Produced by Agitation Granulation.

Abstract

Particle size distribution of fine granules produced by agitation granulation was investigated as a function of the concentration of starch paste. The time course of granulation was investigated in a high speed type mixer using 5% starch paste having a good fluidity and 15% starch paste having no fluidity at all, like a gel. In agitation granulation, aggregation and deaggregation of particles and/or granules occurred simultaneously.At a low concentration of starch paste, massing of the granules, namely the growth of granules, occured mainly during the agitation granulation, since the relatively large amount of free water was available from the paste. Therefore, in this case, only the mean size shifted toward a larger measurement without any change in the width of the granules during the granulation.At a high concentration of starch paste, rapid deaggregation of granules by shear force applied occurred following the formation of large granules immediately after the addition of paste. Since a small amount of water exudes from the paste during the agitation, massing proceeds slowly. This means that in the case of granulation using a high concentration of starch paste, deaggregation proceeds predominantly, so that the size distribution of the granules becomes more narrow. Fine granules may be produced by agitation granulation when a high concentration of starch paste is used and when granulation is executed under sufficient shear or rotation speed that guarantees satisfactory dispersion of the gel.