Physical and aerodynamic properties of paddy and white rice as a function of moisture content

Abstract

Knowledge of the physical properties of agricultural foods and products is important for designing the equipment for processing, transportation, sorting, separation and storing. The objective was to study the aerodynamic properties of paddy and white rice as a function of moisture content. Several physical properties (linear dimensions, geometric mean diameter, sphericity, thousand kernel weight, bulk and kernel densities, porosity) and aerodynamic properties (terminal velocity and drag coefficient) were investigated as a function of moisture content in the range from 5 to 37% (wet basis; w.b.) for paddy and white rice of the two varieties Fajr and Tarom. The principal dimensions, geometric mean diameter, thousand kernel weight and bulk density increased linearly with increasing moisture content for the two varieties, while sphericity decreased in a very gentle linear direction except for the Tarom variety. Kernel density and porosity decreased linearly with an increase in moisture content. The terminal velocity of paddy and white rice increased linearly with an increase in moisture content from 5 to 37% (w.b.). The drag coefficient of white rice decreased linearly while for paddies the two varieties showed a quadratic trend with moisture content increase. The relationships between the measured properties and moisture content of paddy and white rice varieties were obtained and represented by regression equations.