Chemical Engineering & Technology, Vol.33, No.10, 1672-1678, 2010
Adjustable Twin-Slit Rheometer for Shear Viscosity Measurement of Extruded Complex Starchy Melts
An online rheometer with an innovative system of height-adjustable and independently temperature-controlled slits was designed to measure the shear viscosity of extruded wheat bran fiber-containing starchy materials. The range of melt pressures and temperatures, obtained with a die, could be covered by the rheometer. A close ingredient thermomechanical history in the extruder was achieved both with the die and the rheometer, while covering an apparent shear rate from 5 to 30 s(-1). Although minor technical problems remained, first rheological data were obtained and showed a pseudoplastic flow behavior for all recipes. The flow curves were fitted by a power law model. Wheat bran fiber addition influenced both the K-and n-values, leading to more shear-thinning melt behavior and an increase in true shear viscosity. Only a limited effect on these values was found in these preliminary experiments when further increasing the fiber content.