AN ADAPTATION OF THE CASSON EQUATION FOR THE RHEOLOGY OF CHOCOLATE

The generalized Casson equation with exponent m was considered. The plastic viscosities and yield values corresponding to different ranges of shear rate D were calculated for different values of exponent m between 0.5 and 1. All the plastic viscosities tend to about the same value at high shear rates, while at low shear rates all the yield values tend to the same value which is supposed to be the "true" yield value. For the exponent m = 0.6, the yield value is least dependent on the shear rate range and the yield value calculated for D > 5 sec-1 is generally much closer to the "true" yield value than the Casson value (m = 0.5). Therefore, choice of the exponent m = 0.6 is proposed.