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

Abstract

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<sup>–1</sup> to 500 s<sup>–1</sup> 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 R<sup>2</sup> 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.

Importance of rheological properties in enrobing efficiency of dark chocolate: application in wafer products

“…Then, a varied shear rate profile was applied by applying increasing the shear rate from 2 s −1 to 50 s −1 for 180 s, stable shear rate at 50 s −1 for 60 s, and reducing the shear rate from 50 s −1 to 2 s −1 for 180 s. The yield stress and plastic viscosity behaviours of samples were analysed by using the Casson model based on the following eq. (1); where “ τ ” is shear stress, “ τ 0 ” is yield stress, “ η pl ” is Casson plastic viscosity, and “” is shear rate (Kouřilová et al ., 2022).…”

“…where "τ" is shear stress, "τ 0 " is yield stress, "η pl " is Casson plastic viscosity, and "_ γ" is shear rate (Kouřilová et al, 2022).…”