Varietal distinctness in physical and engineering properties of paddy and brown rice from southern India

Paddy and brown rice samples were investigated for its physical characteristics which would aid in designing of the equipment and apparatus for processing of grains as sorting, grading and transportation with ease. Significant difference was observed among the different physical properties as geometrical (length, breadth, thickness, equivalent diameter, sphericity, volume, surface area, aspect ratio) gravimetrical (bulk density, true density, porosity etc.) and frictional characteristic such as angle of repose, hygroscopic properties as moisture and water activity and color of paddy and brown rice kernels. Among geometrical properties length was found the maximum in paddy of Mapillai samba (8.21 mm) and Palkudavazhai brown rice (6.34 mm). Among flow properties, Mapillai samba displayed the maximum value for true density of paddy and brown rice varieties respectively. Hardness was reported in the range of (344.1 ± 14.4-594.88 ± 9.5 and 209.31 ± 4.00-395.99 ± 7.05 N) for different varieties of paddy and brown rice cultivars. The color of the brown rice was read as L*, a*, b* where it varied from 36.22 ± 0.71-61.71 ± 0.81, 4.00 ± 0.18-15.29 ± 0.48 and 16.59 ± 0.52-23.81 ± 0.15 respectively. Brown rice varieties can generally be categorized as short bold, long bold and medium slender as per their length and breadth ratio. The significant differences in physical properties of the various cultivars studied, emphasis on varying processing techniques. The physical properties of selected brown rice varieties studied are widely cultivated in southern India, owing to its high nutraceutical potentials.