Defatted soy flour was extruded in a Brabender single-screw laboratory scale extruder. The effects of barrel temperature, screw speed and feed moisture content on expansion, water absorption index, water hydration capacity and hardness of the extruded products were studied. Response surface methodology, using an incomplete factorial was applied, with combinations of barrel temperature (135, 140, 150, 160, 165degreesC), screw speed (110, 125, 150, 175, 190 rpm), and feed moisture (21, 22, 24, 26, 27%). A continuous increase in barrel temperature and screw speed increased the expansion, water absorption index, water hydration capacity and hardness of the extruded products. The highest specific volume was found with higher barrel temperature and higher screws speeds. Besides, a simultaneous increase of barrel temperature and screw speed increased the water solubility index of the extrudates.3816373