title: The influence of different processing stages on particle size, microstructure, and appearance of dark chocolate.
abstract: 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°, 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 μm of mixed chocolate sample to 3.83 μm, 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.
  
  
  CONCLUSIONS
  Final quality of food dispersions is affected by network and particles characteristics. The deep knowledge of the influence of single processing stage on chocolate microstructural properties is useful in order to improve or modify final product characteristics. ESEM and laser diffraction are suitable techniques to study changes in chocolate microstructure.
authors.affiliation: Interdepartmental Centre for Agri-Food Industrial Research, Alma Mater Studiorum, Univ. of Bologna, Piazza Goidanich, 60, Cesena, Italy.
authors.forename: Virginia
authors.initials: V
authors.lastname: Glicerina
authors.forename: Federica
authors.initials: F
authors.lastname: Balestra
authors.forename: Marco
authors.initials: M
authors.lastname: Dalla Rosa
authors.forename: Bjorn
authors.initials: B
authors.lastname: Bergenhstål
authors.forename: Eva
authors.initials: E
authors.lastname: Tornberg
authors.forename: Santina
authors.initials: S
authors.lastname: Romani
mesh_terms: D002099:Cacao / Q000737:chemistry*; D003116:Color; D005511:Food Handling / Q000379:methods*; D010316:Particle Size
keywords: ESEM; appearance; chocolate; manufacture stages; microstructure; particle size distribution