A capillary-type viscometer was designed to measure the apparent viscosity of the cooked wheat flour dough on-line in a twin-screw extruder. The effects of mean residence time and specific energy were studied in the ranges 20-45 s and 300-800 kJ kg-', respectively. A viscosity model was developed which accounts for effects of wall shear rate, moisture content and specific energy. It was shown that the extent of the cooking reaction is largely determined by the specific energy applied.