Steady shear rheology of rice-blackgram suspensions and suitability of rheological models

Rice-blackgram suspensions having different moisture contents (56-71%) were subjected to rheological testing up to a shear rare of 500 s(-1) using a concentric cylinder rheometer. The unfermented and fermented suspensions showed well pronounced shear-thinning behaviour and exhibited yield stress. The experimentally determined yield stresses were markedly higher in fermented suspensions than in unfermented suspensions. The latter also have a lower flow behaviour index, a lower apparent viscosity, but a higher consistency index. The rheological parameters were sensitive to moisture content in the suspensions, particularly at low moisture levels. Among the common rheological models, the Herschel-Bulkley model fitted the shear rate and shear stress data better (r = 0.992-0.999; p less than or equal to 0.001) than the power law model (0.985-0.994), or the Casson model (0.983-0.993). The measured values of the rheological parameters for the rice-blackgram suspensions used for making dosa, a traditional Indian fermented pancake, are reported. (C) 1997 Elsevier Science Limited.