Predicting the time-dependent rheological behaviour of molten dark chocolate
Nathaniel J. Hendrik1, Flávio H. Marchesini2, Davy Van de Walle1, Koen Dewettinck1
1Department of Food Technology, Safety and Health, Ghent University, Ghent, East Flanders 9000, Belgium
2Department of Materials, Textiles and Chemical Engineering, Ghent University, Zwijnaarde, East Flanders 9052, Belgium
In literature, much focus has been given to investigating the steady-state rheological behaviour of chocolate, and many equations have been proposed to best fit the data obtained for different types of chocolate. However, describing the transient rheological behaviour of chocolate is still challenging. In this work, the time-dependent rheological behaviour of extremely different dark chocolates is investigated. The two chocolates, namely standard and bake-stable dark chocolate, comprise very different formulations and are employed in distinct applications: (i) moulding bars or candies, and (ii) baking. A recently proposed time- dependent constitutive model [Marchesini et al., J. Rheol. 63(2), 247-262 (2019)] is used to describe the observed rheological behaviour. The model is based on a single structure parameter and can take into account thixotropy, elasticity, viscoplasticity, and irreversible effects. The parameters of the model for the two chocolates are obtained from the flow curves and constant shear rate tests. It is shown that the model effectively describes the rheological behaviour of both the standard and bake-stable dark chocolate. These results open the possibility of accurately describing the time-dependent rheological behaviour of a wide range of formulations of fat-based dispersions subjected to different applications in the food industry.
