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, and145 rpm) and feed moisture (31, 33, 35, 37, and 39%) were utilized in 20 runs. The results showed that bulk density ranged from 0.4779±0.003 to 0.7211±0.003 g/cm3; water absorption capacity from 2.52±0.032 to 3.89±0.007 g/g; while oil absorption capacity ranged from 1.12±0.028 to 2.88±0.007 g/g. The best extrusion condition combinations were 110°C barrel temperature, 130 rpm screw speed and 33% feed dampness for bulk density; 105°C barrel temperature, 115 rpm screw speed and 35% feed dampness for water absorption capacity; and 110°C barrel temperature, 130 rpm 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.
Key words: Optimization, functional properties, extrusion, aerial yam, response surface.
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