Impact of grinding technology and particle size on rheological behavior and tribological properties of chocolate compound matrices

In this study, rheological and tribological properties of molten dark and milk chocolate compounds with broader range of fat contents (26-36%) and particle sizes (19-40 μm) were investigated to evaluate the combined effects of refining method, particle size, and fat content on both properties. Results showed that both yield stress and plastic viscosity decreased exponentially with increasing particle size. Refining method significantly influenced these properties: roller-refined chocolate compounds, with bimodal and broader particle size distributions and more irregular shapes, exhibited lower yield stress and viscosity compared to dry-ground samples. Fat content further modulated these effects, enhancing lubrication and reducing flow resistance at higher concentrations. Tribological analysis revealed that the friction coefficient also followed an exponential decay with particle size, plateauing beyond 32 μm. A power-law relationship was observed between the given tribological and rheological parameters, highlighting the distinct mechanisms governing bulk flow and interfacial friction.