Effect of polishing on milling, nutritional properties, and optimization of polishing process parameters for kodo and browntop millets: A response surface methodology approach

Abstract Millets are termed ‘Nutri‐cereals’ as they possess exceptional nutrition profiles. They undergo several processing operations from farm to fork. Polishing is one of the important primary processing operations of millets that facilitates de‐branning. The current work aims to investigate the effect of polishing process parameters like grain's initial moisture content, the rotational speed of polisher, polishing time, on milling yield, nutritional losses of kodo, and browntop millets; to optimize the polishing process through response surface methodology. The polisher speed was found to influence milling and nutritional properties in both the millets whereas, the effect of grain's initial moisture was mostly observed in some responses of browntop millet. Kodo millet polishing at 10% initial moisture content, 1900 rpm for 2 min, and browntop millet polishing at 10% initial moisture content, 1300 rpm for 8 min were obtained as optimum polishing conditions. The degree of polishing and head grain yield at optimum conditions were in the range of 3.5%–4.0%, and 84%–92%, respectively. Less than 15% of nutritional losses were observed at optimum polishing conditions. Practical applications Indiscriminate polishing of millets has become most common industrial practice resulting in less head yield and high nutritional losses. Form the current study, both food processors and researchers get a brief knowledge on the effect of every polishing parameter such as grain moisture content before polishing, rotational speed of abrasive roller in polisher, time of polishing on milling losses and proximate compositions. The optimized process parameters can be directly employed in industrial polishing applications to produce polished grains with higher head yield and very minimal nutritional losses.