The influence of extrusion factors on bulk density, water absorption capacity and oil absorption capacity of aerial yam-soybean flour mixture was examined utilizing a research facility scale single-screw extruder with the flour blending proportion of 25% aerial yam: 75% soybean. Response surface strategy in light of Box-Behken plan at three factors, five levels of barrel temperature (95, 100, 105, 110, and115?), screw speed (85, 100, 115, 130, and145rpm) and feed moisture (31, 33, 35, 37, and 39%) were utilized in 20 runs. Results got showed that bulk density went somewhere in the range of 0.4779±0.003 and 0.7211±0.003g/cm3; water absorption capacity went from 2.52±0.032 to 3.89±0.007g/g; while oil absorption capacity ran somewhere in the range of 1.12±0.028 and 2.88±0.007g/g. The best extrusion condition combinations were 1100C barrel temperature, 130rpm screw speed and 33% feed dampness for bulk density; 1050C barrel temperature, 115rpm screw speed and 35% feed dampness for water absorption capacity; and 1100C barrel temperature, 130rpm screw speed and 37% feed dampness for oil absorption capacity. Analysis of variance showed that barrel temperature, screw speed and feed dampness significantly (p<0.05) affected the bulk density, water absorption capacity and oil absorption capacity of the extrudates.
Keywords: Optimization, functional properties, extrusion, aerial yam, response surface.