Use of rheological plastic models to describe the flow behaviour of unconventional chocolate masses

The chocolate mass behaves like a typical non-Newtonian plastic liquid defined by the yield stress and the plastic shear stress. The rotary rheometer with a cone-plate spindle system was chosen to determine the flow properties of chocolate masses. The effect of shear stress on shear deformation rates was measured at a temperature of 40 °C in an ascending mode from 1 s–1 to 500 s–1 for chocolate samples [white chocolate (WC), ruby chocolate (RC), and caramelised Amber chocolate (AC)]. Plastic models, according to Casson, Bingham and Herschel-Bulkley, were used for the mathematical description of this dependence. The Herschel-Bulkley model was evaluated as the most suitable mathematical model for describing the flow behaviour of unconventional chocolate masses. The Herschel-Bulkley model was chosen based on a high value of the coefficient of determination R2 and a low value of the sum of the square error estimate (SSE). The non-Newtonian plastic behaviour was confirmed, and the yield stress was determined for all types of tested chocolate masses.