STUDIES ON EFFECTS OF CHANGE IN MOISTURE CONTENT ON SOME PHYSICAL, MECHANICAL AND QUALITY PROPERTIES OF TWO PADDY RICE (Oriza sativa L) VARIETIES GROWN IN NIGERIA

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Department of Engineering

ABSTRACT
The aim of this study was to investigate the effects of change in moisture content on some selected physical, mechanical and quality properties of Faro 44 and Jamila varieties of paddy rice. The selected Physical properties were Bulk Density (BD), Angle of Repose (AR), Geometric Mean Diameter (GMD), Mechanical properties include Grain Hardness (GH) and Rupture Force (RF) while the Quality properties include Milling Recovery (MR) and Head Rice Ratio (HRR). The experiment was carried out at three different moisture contents levels of 16 %, 14 % and 12 %. The experiments were conducted using Completely Randomized Design (CRD) at two levels of varieties and three levels of moisture contents. Duncan multiple Range Test and Student Neuman Keuls Test were used to further the grouping and analyze the significant variables. The results shows that the range of values for the bulk density, angle of repose and geometric mean diameter are 530-573 kgm-3, 31.00-32.00 and 3.618-3.786mm, respectively. It was observed that effect of variety is not significant on bulk density. However the effect of moisture content is significant at 5 % level. The effect of interaction of variables is not significant on angle of repose but is significant on the geometric mean diameter. The highest mean Bulk Density of 573kgm-3 was obtained from FARO 44 variety at moisture content of 16%. While the least BD (530Kgm-3) was obtained from Jamila at 14 % moisture content. The highest AR (32o) was obtained at the combination of FARO 44 and moisture content of 16% and 14% respectively. While the least AR of 30o was obtained from Jamila Varieties at 12 % moisture content.. The highest GMD was obtained as 3.78 mm at 16% M.C. while the least GMD was obtained as 3.69 mm at 12 % M.C. It was found that the mean values of grain hardness and rupture force are 36.27-45.07N and 48.92-73.07N, respectively. It was also observed that the effect of all the variables and their interactions on GH and RF are highly significant. The highest GH was obtained as 41.16N for jamila variety and the least GH was obtained as 37.49N for Faro 44 variety. The highest RF (67.80N) was obtained from Jamila variety. While the least RF (57.69N) was obtained from FARO 44 variety. It could be seen that the range of mean values for milling recovery and head rice ratio are 70.15 – 72.87 % and 84.24 – 87.49 % respectively. It was found that the effect of variety on milling recovery is highly significant where as it is not significant on head rice ratio. The effects of interactions on the mean values of both the milling recovery and the head rice ratio are not significant. The highest value of MR (72.87%) was at the interaction of variety and moisture content of 14% which was obtained from Jamila variety. While the least MR (70.15%) was from the interaction of FARO 44 at 12% moisture content. The highest value of HRR (87.49%) was obtained from FARO 44 at 16% moisture content. While the least HRR (84.23%) was obtained in Jamila at 12% moisture content. Jamila paddy rice variety has the highest milling recovery while Faro 44 has the highest head rice ratio. All the varieties has the potentials to compete globally in terms of better rice quality considering the IRRI (2021), World potentials yield milling recovery and head rice ratio of 68-72% and the 80.55 % respectively. It can be concluded that the change in moisture content affect physical, mechanical and quality properties of the selected paddy rice varieties, and also the variety difference influences milling recovery and head rice ratio.