Abstract The deformation properties of thin starch films, approximately 2 μm thick, have been investigated. The films were made by casting from solutions of maize grits extruded at different temperatures and the strain to form shear deformation zones was measured. It was seen that the initial processing conditions of the starch affected the properties of the thin films. The deformation zones were initiated at granule remnants in films made from both unextruded maize grits and grits extruded at low temperatures. More homogeneous films were produced from maize grits extruded at higher temperatures and these films exhibited a higher strain for deformation zone formation. However, degradation was believed to be responsible for lowering this strain for films made from maize grits extruded at the highest temperatures.