Rheology of mustard paste: a controlled stress measurement

Controlled stress measurements on the rheological behaviour of mustard (whole seed, dehulled kernel and meal) pastes were conducted employing a concentric cylinder viscometer in the shear-stress range of 0-20 Pa. The moisture content of the paste was varied between 60% and 80% (dry basis). The different rheological parameters determined included yield stress, flow behaviour index, consistency index and apparent viscosity. Pseudoplastic behaviour with yield stress was observed for all the samples. Yield stress, consistency index and apparent viscosity increased markedly with a decrease in moisture content of the paste but the flow behaviour index decreased. Mustard meal pastes showed the highest apparent viscosity followed by the pastes with hull (whole seed), and with dehulled paste. The Herschel-Bulkley model was suitable for all three types of mustard pastes to correlate (r greater than or equal to 0.983, p less than or equal to 0.001) the shear-stress/shear-rate data. (C) 1999 Elsevier Science Ltd. All rights reserved.