Phenomenological based model for the prediction of the structural changes during chocolate conching process

The conching process is a crucial stage in chocolate manufacturing involving the development of sensory attributes and rheological properties of the product in three phases: dry, plastic, and liquid. This research creates a Phenomenological Based Semi-Physical Model for predicting the chocolate structural changes during conching process. The model was constructed by applying the methodology proposed by Álvarez etal. (2009). Sampling involved all phases of conching for semi-sweet chocolate. The study of the rheological behavior of the chocolate, in the dry and plastic phases involved the extrusion test for the semi-solid samples. For the liquid phase, the rheological data was generated through a bob-cup rheometer. Rheological parameters of the Herschel–Bulkley model including yield stress (σ_o), consistency index (k), and flow index (n) were determined for all samples. A microstructural analysis was conducted to qualitatively validate the structural changes. This analysis revealed coating of the solid particles by fat released from the mechanical impacts on the product. Additionally, the strong relationships between rheological parameters and structural changes are due to the released fat. The created model predicts the viscosity within the accepted range for guaranteeing the rheological quality of product, i.e, 5.3 [ Pa*s] for shear rate of 40 s⁻¹, measured by rheometer. Additionally, operational conditions were varied during the simulation to evaluate the viscosity behavior. The model provides a tool for proposing possible process modifications for optimization without affecting the rheological quality of the product.