Work Index and Milling Efficiency of Size Reduction of Maize Using Plate Mill

Effects of moisture content, speed and feed inlet opening on efficiency of milling using plate mill were determined. Variables were moisture content (10.64, 14.0 16.0, 20.0, 17.36% w. b.), speed (189, 432, 484, 576, 674 rpm) and feed inlet openings (1716, 3900, 4373, 5200, 6084 mm²). Mean work indexes for milling maize grit, meal and flour were 0.40 ± 0.01, 0.13 ± 0.03, and 0.70 ± 0.00 kWh/kg, respectively. Grits, meal, and flour fractions ranged from 48.36 to 75.94%, 21.23 to 48.28% and 1.08 to 4.26%, respectively. The three variables significantly influenced milling efficiency (p<0.05). Optimising grit fraction gave 79.63% grits, 19.75% meals and 1.03% flour. While meal fraction optimisation gave 54.03% grits, 44.89% meals, and 1.97% flour, and flour production optimisation gave 64.82% grits, 30.43% meals, and 4.77% flour. Validation of predicted optimal parameters gave errors of 3.03, 4.04 and 2.50% for grit, meal and flour respectively.