Development of Polisher and Process Optimization for Polishing of Foxtail Millet

Abstract

Foxtail millet is a type of minor millet that has nutritional-rich characteristics. The bran layer in millets contains a considerable amount of antinutritional properties, and grain/flour/product spoilage occurs due to fat in the bran layer. Therefore, the removal of bran from millets can enhance their shelf life. Bran removal from foxtail millet is challenging because of its tiny size. Hence, the study targeted optimizing polishing process parameters for foxtail millet. The effect of process variables such as grain moisture content (8%–16% w.b.), emery roller speed (800–2400 rpm), and polishing time (1–8 min) on polishing characteristics (degree of polishing, head yield, middling yield, and broken content) and proximate composition (protein, fat, crude fiber, ash, and carbohydrate contents) of foxtail millets was studied using the central composite rotatable design (CCRD). Emery roller speed and polishing time significantly affected all responses (p < 0.01). In contrast, grain moisture content had a significant effect only on the degree of polishing (p < 0.05), head, and middling yields (p < 0.01). A numerical optimization technique was adopted to optimize the process parameters of the polisher. The optimum operating conditions were 10% grain moisture content, 1650 rpm of emery roller speed, and 2 min of polishing time. A validation study conducted at optimized conditions revealed no significant difference between the predicted and actual values of responses and considerably less broken content (9.26%). The results of the present study indicate that machinery modified and processes optimized during the study are fairly accepted and can be used to upscale the machine for industrial use.