1 Research in Agricultural Engineering, 68, 2022 Original Paper https://doi.org/10.17221/94/2021-RAE Strength properties of the Bambara kernel (Vigna subterranean) as infuenced by the moisture content and kernel size Nnaemeka R. Nwakuba 1 *, Osita C. Chukwuezie 2 , Maxwell I. Chikwue 1 , Chibuike Ononogbo 3 , Cyprian Dirioha 4 , Merlin Simo-Tagne 5 1 Department Agricultural & Bioresources Engineering, School of Engineering & Engineering Technology, Federal University of Technology, Owerri, Imo State, Nigeria 2 Department Agricultural & Bio-environmental Engineering, School of Engineering Technology, Imo State Polytechnic Umuagwo-Ohaji, Owerri, Imo State, Nigeria 3 Department of Mechanical Engineering, University of Agriculture & Environmental Sciences, Owerri, Imo State, Nigeria 4 Department of Agricultural and Bioresources Engineering, College of Engineering & Engineering Technology, Michael Okpara University of Agriculture, Umudike, Nigeria 5 Nancy-Metz Academy, Nancy, France *Corresponding author: nnaemeka.nwakuba@futo.edu.ng Citation: Nwakuba N.R., Chukwuezie O.C., Chikwue M.I., Ononogbo C., Dirioha C, Simo-Tagne M. (2022): Strength pr- operties of the Bambara kernel (Vigna subterranean) as infuenced by the moisture content and kernel size. Res. Agr. Eng., 68: 00–00. Abstract: Te fracture resistance of food grains is an essential piece of information required for the optimum design and development of agricultural post-harvest machinery. In this study, the strength properties of two varieties of Bambara kernels (TVSU-1395 and TVSU-1353) were examined in terms of the mean rupture force, absorbed energy, and defor- mation as afected by the moisture content and kernel size. To achieve this, a quasi-compressive force was applied on the two varieties of Bambara kernels of varying moisture contents (5.43%, 7.24%, 9.01%, 11.54%, and 13.62% wb) and kernel sizes (small, medium, and large) in between the loading compartments of a universal Testometric device at a 20 mm/min loading rate. Te experiments take ten treatments with 20 replications subjected factorially to a completely randomised design (CRD) into consideration. Te results revealed that the force needed to initiate the kernel fracture increased with an increase in the kernel size and moisture content from 101.44 to 235.06 N and 74.69 to 190.49 N for TVSU-1395 and TVSU-1353, respectively; whereas the energy at the kernel fracture point increased in a range of 0.074 to 0.401 J and 0.062 to 0.141 J for TVSU-1395 and TVSU-1353, respectively. Te kernel deformation increased with the moisture con- tent and size from 0.654 to 3.746 mm. Tese infer that the large kernel size of the TVSU-1395 variety at a 5.4% moisture content had greater compressive strength than the TVSU-1353 variety. Te kernel moisture and size exhibited a strong correlation (0.958 ≤ R 2 ≤ 0.997) with the strength parameters. Te results of this study will help the food industry in de- signing energy-efcient post-harvest equipment for Bambara kernel processing. Further studies may consider the strength attributes of Bambara kernels at varying rates of loading, kernel orientations, and varieties to optimise the best process conditions for the post-harvest handling of diferent Bambara cultivars and develop labour-saving decorticating machines. Keywords: compressive force; rupture, energy; deformation; yield strength Te Bambara (Vigna subterranean) is an African home-grown leguminous food crop, grown most- ly by rural farmers across the African continent. In Nigeria, just as in many African countries, the Bambara nut is generally cultivated by small-hold farmers, typically women, in small land fragments