Comparison of the Brabender Viskograph and the Rapid Visco Analyser .2. Shear conditions

摘要

Shear degradation of starch suspensions prepared in the Brabender Viskograph and the Rapid Visco Analyser (RVA) was examined by means of dynamic rheological and steady shear measurements. Generally, it is assumed that more shear is induced in the RVA because of its paddle geometry and its higher rotating speed. However, for a selected set of native and modified starches the pasting preparation in the RVA was accompanied with less shear degradation than the treatment in the Brabender Viskograph. This was mainly due to the much shorter time of treatment in the RVA. When starch suspensions in both instruments were cooked using the same temperature-time profile, comparable rheological properties were obtained for almost all starch samples investigated. This suggests that the shear conditions in both instruments are quite similar. The rheological properties of starch pastes prepared in the Brabender Viskograph and the RVA appear to be largely dependent on the pasting time, and less dependent on the way in which the shear was applied.