The Influence of Different Processing Stages on Particle Size, Microstructure, and Appearance of Dark Chocolate

The effect of different process stages on microstructural and visual properties of dark chocolate was studied. Samples were obtained at each phase of the manufacture process: mixing, prerefining, refining, conching, and tempering. A laser light diffraction technique and environmental scanning electron microscopy (ESEM) were used to study the particle size distribution (PSD) and to analyze modifications in the network structure. Moreover, colorimetric analyses (L*, h degrees, and C*) were performed on all samples. Each stage influenced in stronger way the microstructural characteristic of products and above all the PSD. Sauter diameter (D [3.2]) decreased from 5.44 mu m of mixed chocolate sample to 3.83 mu m, of the refined one. ESEM analysis also revealed wide variations in the network structure of samples during the process, with an increase of the aggregation and contact point between particles from mixing to refining stage. Samples obtained from the conching and tempering were characterized by small PS, and a less dense aggregate structure. From color results, samples with the finest particles, having larger specific surface area and the smallest diameter, appeared lighter and more saturated than those with coarse particles.