Physical properties of four rice cultivars grown in Indian temperate region

Abstract

Setting up of non-standard unit operations could result in cracking of rice grains during milling, leading to accumulation of broken rice and generation of inferior quality product. Therefore, it is very much important to study physical properties of rice for designing of appropriate rice processing machinery that would minimise post-harvest losses during milling operation. Hence, the present investigation was aimed to study physical properties of four rice cultivars (SR-4, K-39, Mushq Budij and pigmented) grown in Kashmir. Brown and polished rice variants of the four cultivars were studied for grain dimensions, equivalent diameter (ED), geometric mean diameter (GMD), arithmetic mean diameter (AMD), volume, surface area, sphericity, aspect ratio, bulk density (BD), true density (TD), porosity, thousand kernel weight, static coefficient of friction and colour. In general, polishing of rice led to significant (p<0.05) reduction in grain dimensions, volume, surface area, thousand kernel weight (TKW), ‘a’ and ‘b’ values and static coefficient of friction (SCOF). However, there was increase in sphericity, porosity and ‘L’ values of rice kernels after polishing. Amongst cultivars, brown SR-4 rice had the largest length (6.36 mm), GMD (3.30 mm) and AMD (3.73 mm), respectively. However, polished K-39 rice had the highest BD (790.0 kg/m3), TD (1540.0 kg/m3) and porosity (48.70) amongst cultivars. Moreover, unpolished pigmented rice had the highest TKW (23.03 g). In addition, the minimum SCOF was observed when rice kernels were allowed to slide through glass surface with the lowest value observed for pigmented variety (0.40). The present research will be beneficial in fabricating machines for rice processing industry which would be helpful in eliminating post-harvest losses that occur during milling operation.