Among all flour components, starches play a key role during extrusion. Starch undergoes several significant structural changes, which include gelatinization, melting, and fragmentation. This review focuses on transformations in starch during extrusion and their effect on rheological properties. The effect of extrusion operating parameters, such as residence time distribution, thermal and mechanical energy input and pressure inside the die, and their effect on rheological properties are reviewed. The relationships between rheological properties and extrudate expansion and final extrudate texture are discussed. The dependence of starch viscosity on temperature, moisture content, time‐temperature history, shear rate, gelatinization, and fragmentation kinetics during extrusion are reviewed.