The objective of this article is to investigate the effects of fluidized bed granulation with dextrin on moisture sorption and diffusion of Zexie Decoction granules.
The particle characterization was studied by the particle size, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR). The moisture sorption isotherm, equilibrium moisture content (EMC), and moisture diffusion coefficients were determined by using the saturated salt solution method.
The particle size increased from 6.04 μm (powder) to 1201.47 μm (granule). The glass transition temperature of dextrin, Zexie Decoction powder, and granule was 107.13 °C, 94.82 °C, and 126.25 °C. As the increase of temperature, the initial rate of moisture sorption become higher. Furthermore, the initial rate of moisture sorption of Zexie Decoction granules was lower than those of powders and dextrin. The EMC and moisture diffusion coefficients were reduced significantly after granulation (p<0.01). Critical relative humidity and diffusion activation energy of granules were higer than powders.
Results suggested that fluidized bed granulation with dextrin could reduce the hygroscopicity of the Zexie Decoction extract powders and inhibite moisture diffusion, which is mainly related to the microstructure reorganization by fluidized bed granulation and anti-plasticizing effects of dextrin.