Controlled stress rheological measurement of blackgram flour dispersions.

Rheological properties of black gram meal dispersions with different solids concn. were determined using a controlled stress rheometer. Black gram was ground to meal with a particle diam. of 156.8 mum and dispersions for rheological measurements were prepared with solids concn. of 5, 10, 15, 20, 25 and 30% (w/w, dry basis) by addition of distilled water. Rheometry measurements were conducted at 25 0.1C and shear stress was increased from 115 to 2375 mPa to obtain 20 shear rate/shear stress data points. Results suggested that dispersions behaved as a shear thinning fluid with yield stress obeying the Herschel-Bulkley model on the basis of their low values (<less than or equal to>1.4%) for root mean squares between experimental and predicted data. Dispersions also showed a time-dependency and had isotropic loops. Increasing the solids concn. in dispersions increased yield stress, consistency index and apparent viscosity but decreased flow behaviour index. A power law type relationship (r = 0.097, P <less than or equal to> 0.01) was obtained between yield stress and solids concn. It is suggested that these results may be of use in the formulation of slurries/pastes/dispersions for the manufacture of black gram-based foods, especially traditional Indian snack foods.