Evaluation of Rice Milling and Quality of Rice in Ghana

Abstract

The consumption o f rice is on the increase in Ghana. However, local rice is said not to compare well with imported rice. The need to make local rice more competitive is recognized in the light of the increasing role of quality as an important factor of economic competitiveness. This work was aimed at studying the pre- and postharvest technologies for rice, studying rice handling, management and marketing systems, assessing the performance o f rice mills in Ghana and characterising the rice varieties based on the three grain types. Three sets of questionnaires were used to obtain information on pre- and post-harvest factors from rice farmers, middlemen and millers in the Greater Accra, Volta and Eastern regions. Paddy and raw milled rice samples obtained from farms and mills were analysed for quality and grade. Results show that pre- and post-harvest activities are carried out manually. Farmers and middlemen do not have any means of removing high-density foreign materials such as stones from paddy rice. The temperature and relative humidity during drying and storage are not controlled. Moisture content of rice is measured subjectively. Milled rice is sold mainly in small units on the market, by middlemen and is not graded. Small-scale operators who have not had any formal training in the use and adjustment of mills process (mill) rice. Small- and medium-scale, single pass, rubber roller mills predominate in the study area. All mills produce under capacity with milling yields of 45-75 %. The mills do not have precise maintenance schedule. Milled rice from mills could be classified as Ghana rice grades 1 to 5 based on content of extraneous matter, discoloured and chalky grains. Broken kernels of samples ranged between 21-81 %. Thus in terms o f percentage broken, mill rice does not fall within specifications of Ghana standard for milled rice. Samples had lower grade than the lowest grade of GS 61: 1990. The very high percentage of broken kernels makes local rice less competitive. Results also indicated that rice samples could be classified as long, medium and short grain types based on standard specifications of Ghana (GS 61:1990), Codex Alimentarius, and the FAO. Most mills produce low degree milled rice. Bulk density values ranged between 793.7 kgm'3 for Wita 9 to 848 kgm‘3 for Emo korkor. This was partly affected by moisture content (r2 = 0.21). Colour, translucency, fat, protein, and ash were significantly different (p < 0.05) among the samples. Protein, fat and ash content ranged between 6.45- 10.45 %; 0.11-1.56 %; and 0.24-0.79 % respectively. Rice kernels exhibited alkalispreading values of 2-6 and were mostly high amylose varieties. TOX 3108 recorded the highest pasting temperature of 82.6°C while the lowest pasting temperature of 62.3°C was recorded by TOX 18447. Rice samples showed peak viscosity' of 760- 1165 BU and relatively high viscosity (755-1040 BU) of the cooked paste on cooling to 50°C except Emo korkor, which had cooled paste viscosity o f 720 BU, indicative of medium and short-grain types. The rice varieties overlap in the physicochemical properties of the 3-grain types. A number of improvements could therefore be made to rice production and processing procedure in Ghana.