Microstructure and mechanical properties related to particle size distribution and composition in dark chocolate

Emmanuel Ohene Afoakwa, A. Paterson, Mark Fowler, Joselio Vieira

Research output: Contribution to journalArticlepeer-review

81 Citations (Scopus)


Composition in dark chocolate was varied and the effects determined on microstructure, using light microscopy, and mechanical properties of molten and tempered chocolates, using a TA.HD Plus Texture Analyser. Compositional parameters were particle size distribution (PSD) (D90 of 18, 25, 35 and 50 μm), fat (25%, 30% and 35%) and lecithin (0.3% and 0.5%) contents. Micrographs revealed wide variations in sugar crystalline network structure and inter-particle interaction strengths related to PSD and fat level. Samples containing 25% fat had more crystal agglomerates, well flocculated with greater particle-to-particle interaction strengths than those with higher (30% and 35%) fat contents. Increasing the D90 to 35-50 μm caused broadening of the PSD, with particles becoming coarser, which were similar at all fat levels. Mechanical analysis showed that PSD, fat and lecithin content significantly influenced firmness of molten chocolate and hardness of solid (tempered) chocolate with significant interactions among factors. Particle size was inversely correlated with firmness (1235-173 g) and hardness (7062-5546 g). Greatest effect of PSD was with 25% fat and 0.3% lecithin. With higher fat and lecithin contents, the PSD influence was reduced. It was concluded that PSD, fat and lecithin contents and their interactions were central to mechanical properties of dark chocolates.
Original languageEnglish
Pages (from-to)111-119
Number of pages8
JournalInternational Journal of Food Science and Technology
Issue number1
Publication statusPublished - Sep 2007


  • chocolate
  • fat content
  • lecithin
  • mechanical properties
  • microstructure
  • particle size distribution
  • texture


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