Effect of process variables on physical properties of corn (variety: popcorn: sugar baby) extrudates

Abstract

As the world population continues to grow, the demand for human food and animal feed grows exponentially. Corn flour fortified with rice bran and pigeon pea brokens was extruded using a twin-screw extruder. Blends were prepared with three levels of feed composition (92:4:4, 94:3:3 and 96:2:2; corn: rice barn: pigeonpea broken), feed moisture (15, 17.5 and 20%) and extrusion condition three-barrel temperatures (110, 120, and 130 °C). The extruded products were evaluated for their physical properties like expansion ratio, moisture retention, bulk density, mass flow rate, specific mechanical energy, colour value (L* value). A Box-Behnken experimental design and response surface methodology was used to evaluate the significance of independent and interaction effects of extrusion process variables. The independent variables had significant (p≤0.05) effects on physical properties of extrudates. The optimized condition for the preparation of corn based extruded product was found to be 130 °C temperature, 20 % of feed moisture and 92:4:4 feed composition at constant screw speed of 350 rpm. The optimized extrusion processing parameters showed higher value of expansion ratio (3.21), mass flow rate (4.01 g/s) and L* value (65.42), and minimum values of bulk density (0.13 g/cc), moisture retention (24.55%) and specific mechanical energy (25.29 kJ/kg). As per the design expert software the selected optimized process condition was found to be desirability of 0.698.