Impact of Thermal Pretreatment on the Processing Characteristics of Kodo Millet

Abstract

Kodo millet (Paspalum scrobiculatum) is a nutrient-dense millet grain classified among difficult-to-dehull millets; however, its wider commercial utilisation remains severely constrained by a tightly adhered multilayered husk and high susceptibility to grain breakage during dehulling. This study investigated the effects of thermal pretreatment parameters, i.e., infrared heating before dehulling, on processing characteristics, namely dehulling efficiency, head recovery, and broken percentage, at variable infrared voltages (200, 220, and 240 V) and treatment times (3–7 min). A small prototype infrared treatment system with a batch capacity of 500 g was developed by ICAR-CIPHET, Ludhiana. The system consisted of a 250 W IR bulb, a manually rotating plate with a diameter of 30 cm, and a Variac for setting different voltages. Thermal preprocessing induced deliberate microstructural modifications at the husk–endosperm interface, facilitating husk loosening and significantly improving the mechanical resistance of the grain. Under the treatment condition of 240 V for 7 min, dehulling efficiency increased to 84.76%, while head recovery reached 58.77%, accompanied by a reduction in the broken percentage from 12.34% to 5.79% compared with untreated controls. Overall, thermal preprocessing offers an effective, sustainable approach to mitigate milling losses, enhance head recovery, and preserve techno-functional traits, providing an operational pathway for commercial processing of kodo millet.