Design, Fabrication, and Performance Evaluation of a Hybrid Auger–Impact Dehuller for Small-Scale Maize and Cowpea Processing

Despite advances in grain dehulling technologies, the mechanical removal of seed coats and pericarps remains challenging, particularly in sub-Saharan Africa, where substantial variation in grain physical and mechanical properties can adversely affect dehulling performance. Conventional dehulling methods are often associated with excessive grain breakage, low processing yield, and product quality deterioration. This study aimed to design, fabricate, and evaluate the performance of a hybrid auger–impact dehuller for cowpea and maize. The developed machine incorporates adjustable rotor speed and clearance settings, a 0.01 m3 dehulling chamber designed to facilitate the recovery of broken grains, and an integrated pneumatic separation system for the effective removal of hulls. Dehulling is achieved through the combined effects of compression, shear, friction, and impact forces. Machine performance was evaluated under different operating conditions, including rotor speed (95 and 229 rpm), processing time (15 and 30 min), and soaking time (10–80 min). Overall, the hybrid auger–impact dehuller exhibited variable performance across the tested rotor speeds, processing times, and grain types. For cowpea, at 95 rpm and a processing time of 15 min, dehulling efficiency ranged from 5.95 to 83.71%, grain breakage from 0.20 to 6.07%, total dehulled grain yield from 5.80 to 80.00%, and pneumatic separation loss from 0 to 5.64%. At 229 rpm and a processing time of 15 min, across the tested cowpea varieties, dehulling efficiency ranged from 52.85 to 96.62%, grain breakage from 3.13 to 11.85%, total dehulled grain yield from 28.94 to 77.31%, and pneumatic separation loss from 2.34 to 3.96%. For maize, evaluated at 200 rpm for 30 min following soaking durations of 10, 20, 40, and 80 min, dehulling efficiency ranged from 88.11 to 93.35%, grain breakage from 3.97 to 5.30%, total dehulled grain yield from 74.10 to 77.66%, and pneumatic separation loss from 2.33 to 4.87%. These results characterize the machine’s performance under the tested operating conditions and highlight the trade-offs among dehulling efficiency, grain breakage, grain yield, and pneumatic separation loss. The findings demonstrate the potential of the hybrid auger–impact dehuller for processing cowpea and maize, with potential applications in reducing post-harvest losses and supporting grain processing by small- and medium-scale operators in sub-Saharan Africa.