Improving Processing Characteristics of Difficult-to-Dehull Millet through Continuous Microwave Preprocessing

Kodo millet (Paspalum scrobiculatum L.) is difficult to dehull because of its multilayered, closely adhering husk, which can reduce head grain recovery during mechanical processing. This study evaluated continuous microwave preprocessing to improve dehulling efficiency and head recovery while limiting kernel breakage. Experiments were conducted in July 2026 at ICAR–Central Institute of Post-Harvest Engineering and Technology, Ludhiana, using Kodo millet cultivar JK-439. A three-factor, three-level Box–Behnken design comprising 17 runs examined microwave power levels of 60–100%, treatment durations of 60–120 s and initial grain moisture contents of 12–16% (wet basis). Treated grains were subsequently milled in a single pass using a rubber roll sheller, and their performance was compared with that of untreated grain. The untreated control recorded 76.68% dehulling efficiency, 52.57% head recovery and 8.05% kernel breakage. Numerical optimisation identified microwave power of 81.4%, treatment duration of 91.8 s and grain moisture content of 14.48% as preferred conditions, with a reported desirability of 0.964. Triplicate validation trials under these conditions yielded 86.62% dehulling efficiency, 61.98% head recovery and 7.25% breakage. Compared with the control, these outcomes represent increases of 9.94 and 9.41 percentage points in dehulling efficiency and head recovery, respectively, and a 0.80-percentage-point reduction in breakage. Continuous microwave preprocessing therefore improved the measured milling outcomes under the conditions evaluated.