ABSTRACTA review of fundamental and engineering aspects of extrusion in a single‐screw is given. Attention is focussed on flow patterns, flow rates, residence time distributions and power consumption as a function of extruder design and screw rotation speed. The relationship for these engineering variables in extrusion of a purely Newtonian liquid and a power law liquid are reviewed. Where possible these relationships are compared with experimental results from the literature (corn‐grits) and with our own measurements on biopolymers (corn‐grits, defatted soy flour, modified di‐amylo