AbstractCorn starch was phosphated on a Brabender single screw extruder at different extrusion temperatures, sodium tripolyphosphate (STP) concentration and pH of the medium. The highest degree of substitution (DS) was obtained at extrusion temperature of 200°C, STP concentration equal or superior of 1.4g/100mL of water and pH of 8.5. The DS was related to paste clarity while the extrusion process, to the water absorption index and water solubility index, independently of the DS