ORIGINAL ARTICLE Design, development, and evaluation of a motorized rice grader John O. Ojediran | Clinton E. Okonkwo | Samuel A. Alake | Elijah A. Alhassan | Adeniyi T. Olayanju Department of Agricultural and Biosystems Engineering, Landmark University, Omu-Aran, Kwara State, Nigeria Correspondence Clinton E. Okonkwo, Department of Agricultural and Biosystems Engineering, Landmark University, Omu-Aran, Kwara State, Nigeria. Email: okonkwo.emeka@lmu.edu.ng Abstract The design and construction of a motorized rice grader were undertaken to classify rice grains into the head rice and broken rice. Three (3) screens of decreasing diameters were used inclined at angles ranging from 6, 8, and 16 0 and driven by a 5 hp motor to cause agitation and a pneumatic mechanism for blowing light chaff material. The performance efficiency of the developed machine was evaluated with milled rice at 15% moisture content (wet basis) at different feed gate levels (FGL) (5 to 20 mm). The result indicated decreased grading efficiency (GE) and product purity (PP) with increased FGL, increased throughput capacity (TPC) and tray loss (TL) with increased FGL. The highest GE and PP were 91.67 and 90.97% at 5 mm FGO, while the highest TPC and TL were achieved at 20 mm FGL as 0.08 kg/s and 1.06%, respectively. The feed gate levels (5 to 20 mm) had a significant effect on the performance efficiencies investigated. Practical applications After rice milling, there are usually broken rice grains in mixture with head rice. The developed motorized rice grader is useful in separating broken rice grains from the milled rice. This machine would help increase the quality of rice produced by the local or commercial processors. In addition, the time and drudgery associated with manual sorting are reduced. 1 | INTRODUCTION Rice (Oryza sativa) is a staple food consumed by about half of the global population. This is because it supplies a quarter of the calo- rific intake of the human race (Olugboji & Jiya, 2014). Rice is grown in many nations of the world, led by China and India (Prakash, Someswararao, & Das, 2014). In Nigeria, almost all the ethnic groups take rice as a delicacy (Gbabo, Abdullahi, & Kuku, 2014; Gbabo & Ndagi, 2014). A better quality of rice has been on the increase in Nige- ria. Reduction in rice post-harvest losses is a necessity toward ensuring global food. Traditional parboiling, drying, and none-suitable de-husker have contributed to a high percentage of breakages in rice, which reduces its market value. For the high purchase of rice grain, some parameters considered include; size, shape, color, head rice yield, and percentage broken kernels. Grading of milled rice describes the separation of a broken rice grain from the head rice. Furthermore, the local demand for graded quality rice is also increasing, thus making grading of rice a necessity. Classification of a milled rice grain is done based on its length: 1/1 head rice, 7/8 head rice, 6/8 large broken, 5/8 large broken, 4/8 large broken, 3/8 small broken, 2/8 small broken, and 1/8 small broken (Someswararao, Mahato, Namgial, Huda, & Das, 2017). Since the inspection of rice quality by humans is neither objective nor reliable, automation with the use of machines must be applied for the desir- able result (Kaur & Singh, 2013). In literature, Lloyd, Cnossen, and Siebenmorgen (2001) evaluated two methods of separating broken rice from head rice yield using a shaker table and a machine vision system called the Grain Check. Tabatabaeefar, Aghagoolzadeh, and Mobli (2003) designed and devel- oped a sieving and grading machine for chickpea. Jose and Engelbert Received: 29 September 2019 Revised: 3 November 2019 Accepted: 21 November 2019 DOI: 10.1111/jfpe.13336 J Food Process Eng. 2019;e13336. wileyonlinelibrary.com/journal/jfpe © 2019 Wiley Periodicals, Inc. 1 of 8 https://doi.org/10.1111/jfpe.13336