Effect of moisture content and particle size on grinding kinetics and flowability of balloon flower (Platycodon grandiflorum)

In this study, the grinding kinetics and the flowability of balloon flowers (BFs) with various moisture contents (8, 12, and 20%) were determined. Three semi-empirical grinding models (Bond, Kick, and Rittinger) were applied to describe the BFs' grinding process. A lower moisture content resulted in a decreased grinding constant value (Bond's index). Based on the kinetics of particles during grinding, a sigmoid model was developed which successfully described changes in the particle sizes of BFs with various moisture contents during the grinding process except for smaller ones (< 0.60 mm) with a high moisture content (20%). The flow function at different particle sizes was not consistently correlated with results regarding the internal friction angle. This might be due to different particle shapes and sizes of BFs. The poorest flowability was observed for BF powder with the smallest particle size.