MODIFICATION AND PERFORMANCE EVALUATION OF A SOAKED COWPEA (Vigna unguiculata) DEHULLING AND SEPARATING MACHINE

Abstract

ABSTRACT The most common method of dehulling and separation of soaked cowpea seeds in Nigeria is the manual method of rubbing between the thumb or the use of mortar and pestle to dehull the soaked cowpea seed coat. This method is time consuming and has high demand of human energy. Although, there are some available locally dehulling and separating machines that have been developed by institutions like Nigerian Stored Products Research Institute, Kano and Department of Agricultural and Biosystems Engineering, University of Ilorin. These machines developed by these institutions has limitation in terms of water recycling system. Hence, this study is to modified the existing dehulling and separating machine. A soaked cowpea dehulling and separating machine was developed using locally available materials to reduce drudgery attached to traditional dehulling of the seeds. The machine consist of dehulling unit made from 2.0 mm thick galvanized metal sheet, where the dehulling operation takes place, and a separating unit where hulls and cotyledon are separated. The dehulling mechanisms obtain its drive from a 2 hp electric motor with a speed of 1430 rpm. The principle of operation of the machine is by rubbing action principle between the cylindrical drum and the wall of the dehulling chamber. The performance evaluation of the cowpea dehulling and separating machine was done using D-optimal factorial experiment in a Randomized Complete Block Design involving speed, soaking time and cowpea variety each at 3, 3, and 3 levels respectively. These were replicated three times. The developed soaked cowpea de-hulling and separating machine performs optimally at 250 rpm speed, 8 minutes soaking time, and with Kananado variety. The test performance carried out on the machine showed that the effective de-hulling efficiency, separating efficiency, and output capacity obtained were 96.2%, 67.0%, 40.8kg/h/batch respectively. Generally, the performance of the modified machine was better in terms of dehulling and output capacity while the existing machine excel in terms of separation of cowpea seeds.