Size characterization of moringa (Moringa oleifera) seeds and optimization of the dehulling process

The size of moringa seeds was characterized, and the dehulling process parameters were optimized. The effects of moisture content, feed rate, operational speed, and beater-drum clearance on dehulling efficiency were studied. A 4 x 5 central composite rotatable design was employed, and multiple linear regression was utilized for analyzing data at 5% significant level. Experimental results were used to validate predicted optimum conditions. Processing parameters were related to dehulling efficiency using developed mathematical models. Maximum dehulling efficiencies of 81.14, 85.66, and 96.03% were obtained for the small, medium, and big sizes respectively. The moringa seed size and other processing factors were found to have significant effect on the dehulling efficiency. Predicted optimum values of 83.62, 88.18, and 99.69% for small-, medium-, and big-sized categories, respectively, were obtained at 9.38%wet basis moisture content, 1.35 kg/min feed rate, 844.61 rpm dehulling speed, and 6.38 mm beater-drum clearance. The experimental values were 84.33, 88.97, and 99.76% for small-, medium-, and big-sized categories, respectively, under the optimal conditions. Variations between values obtained experimentally and predicted were negligible and statistically insignificant; therefore, the selected models were adjudged to adequately predict the dehulling efficiencies for all the size categories. Practical Applications Despite the benefits derived from moringa seeds, dehulling of the seeds has been a tedious operation. Considering this, a moringa dehuller was developed, and the performance was evaluated. However, for an efficient system, it is imperative to understand the mechanisms of the various important factors influencing the dehulling process and their interactions. The approach of considering one factor per time consumes time and is unrealistic to obtain the right optimal conditions; making it impractical to optimize the dehulling process using such approach. Considering this, RSM was employed to optimize the moringa dehulling process parameters. Mathematical models were developed to predict responses during the dehulling process using RSM. For efficient machine performance, the seeds were graded into various sizes and the effects of moisture content, feed rate, operational speed, and beater-drum clearance on the dehulling efficiency were investigated and optimized. Results obtained in the study would be useful to moringa seed processors.