Effect of moisture content on crackability of bambara groundnut using a centrifugal cracker
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Department of Mechanical Engineering, University of Maiduguri, Maiduguri, Nigeria
Department of Mechanical Engineering, Ramat Polytechnic, Maiduguri, Nigeria
Int. Agrophys. 2007, 21(2): 179-184
One of the most tedious operations in processing bambara groundnut is the shelling operation. However, moisture content normally affects the handling and processing of agromaterials, such as nut shelling/cracking. This study was conducted to determine the effect of moisture content on shelling efficiency of bambara groundnut using a centrifugal cracker. A 50 kg bag of bambara groundnut obtained from Damboa Local Government Area of Borno State, Nigeria, was divided into three groups. These groups were prepared for tests by soaking them in ordinary water at room temperature for different periods of 0, 60 and 90 min to obtain different levels of moisture content. Moisture content of each sample was determined by oven drying at 130°C for 6 h. The moisture content levels were found to be 5.3, 9.6, and 12.2% (d.b.) for samples A, B and C, respectively. The samples were subjected to impact energy through a centrifugal impaction device operating at an angular velocity of 1920 r.p.m., using three different types of impellers. Data obtained on the percentage of fully shelled pods and unbroken seeds, fully shelled pods with broken seeds, partially shelled pods and unshelled pods were statistically analysed. Results showed that both moisture content and impeller angulations have a significant effect on these performance indices. The most effective performance was obtained at moisture content of 5.3% (d.b.), at which the shelling efficiency, percentage of damaged seeds, percentage of partially shelled pods and percentage of unshelled pods were 96, 3.4, 0.6 and 0, 86.6, 3.6, 5.6 and 4.2, 85, 2.4, 5.4, and 7.2% for the forward facing impeller, radially positioned impeller and the backward facing impeller, respectively. The study further showed that development of a centrifugal impact bambara groundnut sheller with winnower would eliminate the tediousness of the present manual pod cracking methods.
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