Extrusion processing characteristics of whole grain flours of select major millets (foxtail, finger, and pearl)

Abstract Extrusion processing characteristics of whole grain flours of three major millets (finger, foxtail and pearl) were studied. Impacts of the extrusion processing conditions, including moisture (15, 17.5 and 20%), screw speed (300, 350 and 400 rpm) and barrel temperature (110, 120 and 130 °C), on the physicochemical properties of the millet extrudates was evaluated. Quality parameters of extrudates including, expansion ratio (ER), water solubility index (WSI), water absorption index (WAI) were measured. Variations in the structural properties were confirmed by macrostructural observation using scanning electron microscopy (SEM). Foxtail extrudates showed the highest expansion ratio (4.41) followed by pearl millet (3.78) and finger millet extrudates (3.18). WAI values for the foxtail millet, pearl millet and the finger millet extrudates were 4.18 g/g, 2.69 g/g and 3.54 g/g. respectively. Overall, the foxtail millet gave the best response, with the highest ER value achieved at 130 °C, with least SME input. The results highlight the potential use of whole millets flours in the development of direct expanded extruded foods.