Normally in extrusion cooking, a reduction in the size of the die aperture causes an increase in die resistance and, therefore, an increase in die pressure. However with some experimental recipes based on rice flour following a reduction in the diameter of twin circular dies from 4 to 3 mm, the reverse was found to be true under certain conditions of screw speed, using a screw system comprised of separated kneading and die head pumping zones in an APV Baker twin-screw extruder This behaviour was attributed to phenomena related to both the screw design, in which the screw has a high pumping capacity following the shearing zone, and to a relatively low biopolymer melt viscosity in the barrel.