Some physical characteristics of cassava starch extruded using a single-screw extruder, varying acid concentration, feed moisture content and barrel temperature were evaluated using surface response methodology. The combined effects of different concentrations of sulphuric acid and extruder parameters provided unique physical functionality to the extruded cassava starch. Product hardness and torque value was highly significant for three variables. The addition of sulphuric acid (0.06N) during extrusion cooking gave the highest values for expansion and softness of the extruded samples. The highest torque values (60-70 Nm) were for the samples extruded at the lowest moisture content, while the lowest torque values (23.0-26.0 Nm) were for the samples extruded at the highest values of feed moisture and barrel temperature.
Single-screw extruder; sulphuric acid; hardness; cassava starch
