Moisture content and application rates of inert dust: effects on dust and wheat physical properties

Grain protectants such as inert dust help prevent quality deterioration during post-harvest storage. Understanding the physical characteristics of inert dust and inert dust treated wheat kernels could help develop solutions to flow problems of stored grain. This research investigated the effects of the moisture content of a synthetic amorphous zeolite and the rates of application on some physical properties of the amorphous zeolite and wheat kernels. Three levels of moisture (2.0%, 6.0%, and 10.0%) of the zeolite were applied at three rates (0.5 g/kg, 1.0 g/kg, and 2.0 g/kg) on 100 g wheat samples (10% m.c, wet basis) in triplicates. Image analysis, laser diffraction, Thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM), gas pycnometry, and the Single-Kernel Characterization System (SKCS) were used to characterize the physical properties. The particle size of the amorphous dust increased with increasing moisture content. Conversely, shape parameters (circularity, aspect ratio, convexity, and solidity) generally decreased with increasing dust moisture contents. When wheat was mixed with the amorphous dust at increasing rates and moisture levels, the bulk density of wheat decreased, while the tapped density and the angle of repose increased, resulting in higher Hausner ratios and Carr Index values. Treating wheat with the amorphous dust at the highest moisture (35%) and application rate (2.0 g/kg) caused the treated wheat to transition from an acceptable flowability to a poor flowability along with a decrease in wheat kernel hardness. Our data suggest, however, that a range of moisture content (2-6%) and an application rate (0.5 g/kg) mitigate the adverse effects on wheat flowability. This study also highlights the importance of drying any amorphous dust or allowing dust to equilibrate to the experiment temperature before conducting tests on physical properties.