Influence of Extrusion Conditions on the Physical Characteristics of Pearl Millet–Based Extrudates

Abstract

In this study, a composite flour mixture consisting of 70% pearl millet and 30% chickpea flour was processed into extruded snacks using a twin-screw extruder to understand the potential of optimized extrusion technology for producing nutritious and commercially viable millet-based snack products that support sustainable food systems. A composite flour mixture of pearl millet and chickpea was formulated in a 7:3 ratio. The sample was moistened and allowed to equilibrate at room temperature overnight and extruded using a twin-screw extruder at different die temperatures, screw speeds, and feed moisture levels. The physical and functional attributes of the extrudates were examined using Response Surface Methodology. The highest expansion ratio (4.25) was achieved at 150 °C, a screw speed of 275 rpm, and a moisture content of 16%. The bulk density of the products varied from 45.25 to 71.25 kg/m 3 , and the water solubility index ranged from 21.15% to 32.55%. Increased die temperature along with moderate screw speeds promoted greater expansion and correspondingly reduced the density. The fitted regression models demonstrated strong predictive performance with R 2 values exceeding 0.87. The study of combined effects of temperature, screw speed and moisture on product quality using RSM for optimization generates modern process, property relationships for millet-based extrudates. The high expansion ratio (4.25) and strong regression predictability (R 2 > 0.87) highlight the feasibility of producing commercially viable, sustainable, and nutrient-dense millet snacks using extruders, an area with limited prior scientific reporting.