Locally processed rice (Oryza sativa L.) is characterized with high percentage of
broken grains and impurities which impair the quality and reduces the market value.
Reducing the proportion of broken rice and impurities after milling remains a challenge.
There is therefore a need to develop a machine which cleans and grades the rice kernels
based on quality. The objective of this work was to develop a cleaner - grader to improve
the quality of milled rice.
The physical and aerodynamic properties of six rice cultivars (ITA 150, FARO 44,
FARO 52, NERICA 1, IGBEMO 1 and IGBEMO II) were determined using ASAE
Standards. Based on these properties, a three sieve oscillating cleaner - grader machine was
developed. Samples from the six rice varieties were milled using No 1 rice huller and
milling characteristics were evaluated according to NIS 230 Standards. The machine was
tested to determine cleaning performance index and grading efficiency of the rice cultivars.
The tilt angle of the top and bottom sieves were fixed at 2 and 15o
, the intermediate sieve
was set at 2, 4 and 6o
and the blower was inclined at 0 and 5
. Data were analysed using
ANOVA and descriptive statistics.
The moisture content of the rice cultivars during milling varied from 10.7 to 12.5%
and 11.0 to 13.6% in the raw and parboiled paddy respectively. The mean angle of repose
± 0.4 and the mean co efficient of friction was 0.3 ± 0.01. The spherical mean
ranged from 2.9 to 3.5 mm and was significantly different (p˂0.05) in Igbemo II cultivar
when compared with other cultivars. The sphericity was within 0.41 to 0.5; the bulk
density ranged from 1.34 to 1.38 gcm-3
, while the terminal velocity varied from 4.8 to 6.4 ms-1
.The machine was developed to operate at a fan speed of 240 rpm, air velocity of 4.8
ms-1 with aperture diameter of 3, 5.5 and 7 mm for bottom, intermediate and top sieves
respectively. The head rice yield ranged from 22.3 to 34.1% and 44.8 to 55% for the raw
and parboiled milled respectively. The percentages of broken grains obtained during
milling of raw and parboiled rice were further reduced by 41.5 and 64.8% respectively
with the use of the machine. The cleaning performance index of the machine ranged from
0.6 to 0.9; the highest occurred at a tilt angle of 4o
and blower inclination of 5o
for raw ITA
150. The grading efficiency ranged from 61.4 - 84.8% and 69.0 to 94.5% for raw and
parboiled milled rice respectively. The highest values of 84.8% and 94.5% were obtained
in raw FARO 44 at a tilt angle of 2
and in parboiled ITA 150 at a tilt angle of 6
respectively with blower inclination of 5o
The use of the cleaning and grading machine after milling has substantially reduced
broken kernels of locally processed rice in the raw and parboiled milled rice thereby
enhancing the quality.
CDR, C (2021). Development of a Cleaning and Grading Machine to Improve the QUality of Milled Rice (Oryza sativa L.). Afribary.com: Retrieved April 10, 2021, from https://afribary.com/works/development-of-a-cleaning-and-grading-machine-to-improve-the-quality-of-milled-rice-oryza-sativa-l
Coalition, CDR. "Development of a Cleaning and Grading Machine to Improve the QUality of Milled Rice (Oryza sativa L.)" Afribary.com. Afribary.com, 03 Apr. 2021, https://afribary.com/works/development-of-a-cleaning-and-grading-machine-to-improve-the-quality-of-milled-rice-oryza-sativa-l . Accessed 10 Apr. 2021.
Coalition, CDR. "Development of a Cleaning and Grading Machine to Improve the QUality of Milled Rice (Oryza sativa L.)". Afribary.com, Afribary.com, 03 Apr. 2021. Web. 10 Apr. 2021. < https://afribary.com/works/development-of-a-cleaning-and-grading-machine-to-improve-the-quality-of-milled-rice-oryza-sativa-l >.
Coalition, CDR. "Development of a Cleaning and Grading Machine to Improve the QUality of Milled Rice (Oryza sativa L.)" Afribary.com (2021). Accessed April 10, 2021. https://afribary.com/works/development-of-a-cleaning-and-grading-machine-to-improve-the-quality-of-milled-rice-oryza-sativa-l