Adjustable Twin‐Slit Rheometer for Shear Viscosity Measurement of Extruded Complex Starchy Melts

Abstract

AbstractAn 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.