Rheological Studies on Starch — Flow Behaviour of Wheat Starch Pastes

Flow behaviour of wheat starch pastes has been studied over a large range of concentrations (0.3 to 8%) with a coaxial cylinders viscometer (Rheomat 30) and a highly sensitive viscometer (Low‐Shear 30). The flow curves indicated a non‐Newtonian and shear thinning behaviour with a Newtonian limit viscosity η° between 0.3% and 1.5%. Above this concentration, the flow curves could be described by an Ostwald‐De Waele equation over a limited range of shear rates. Moreover, for the highest concentrations a tendency to a yield stress was displayed. By comparing the effect on the flow curves of three preparation procedures, large differences were observed which were interpreted on the basis of particles dispersed in a macromolecular medium. The size of these particles and the composition of this macromolecular medium are determining for this flow behaviour.