Physical properties of parboiled milled local rice varieties marketed in South-East Nigeria.

Abstract

Physical properties of rice grain is important for mechanisation and proper post-harvest handling operations to prevent post-harvest loss and achieve high head-rice grains. Knowledge on the physical properties of Nigeria's local rice is limited which has led to losses and production of low quality grains characterised by large amount of brokens and poor appearance. Physical properties of 18 local and 3 imported rice varieties (control), were evaluated using standard methods. The physical properties evaluated were grain dimensions, Arithmetic mean diameter, (AMD) geometric mean diameter (GMD), square mean diameter (SMD), sphericity, aspect ratio, surface area, general appearance, dockage and aroma. Most (77.78%) of the local rice varieties were long grain rice, 50% were slender grains and 50% were bold grains, 77.78% of the local rice varieties were heavy grains. The AMD, GMD and SMD of local rice grains ranged from 3.29-3.86mm, 8.02-10.36mm and 4.75-5.82mm, respectively. The sphericity, aspect ratio and surface area were in the range of 51.25-59.23%, 0.31-0.46 and 21.87-29.44mm2, respectively. A significant percentage (50%) of the local rice were grey coloured and unappealing in appearance. All the local rice varieties had dockage (5-70%) while the imported rice varieties had no dockage and possessed translucent light-cream to yellow shades and were appealing in appearance. These data are important for correct coupling and adjustment of post-harvest processing machine to prevent losses and produce high head-rice with appealing appearance.