Scientific research

Dark semi-sweet chocolate samples, obtained at various times during conching, were cooled and prepared for examination by scanning electron microscopy (SEM) in an attempt to observe structural changes during conching. In addition, ingredient mixtures containing known amounts of cocoa solids, microcrystalline cellulose, starch, sucrose and lecithin were studied to correctly identify the components of chocolate. Pulverized sucrose particles were easily characterized by their smooth surfaces and heterogeneous shapes. Defatted chocolate liquor was rougher in appearance and smaller in size than sucrose. Cellular detail of the cocoa bean was evident in liquor even after the disruptive effect of refining. Lecithin, when added to liquor-sugar and cocoa butter-sugar mixtures, had a remarkable and rapid effect in reducing three-dimensional structure. When processed chocolates from four different conches were examined by SEM, little or no differences were observed in the size or shape of the sugar or liquor particles as conching proceeded. Surface smoothening, however, was noted and attributed to the homogenization or spreading of cocoa butter during conching. When lecithin was added to chocolate during conching the surfaces were reduced and appeared to flatten. The effect of lecithin in reducing surface tension was also supported by viscometry. Viscometric measurements taken at this time showed that the increase in fluidity was accompanied by a sharp and rapid decrease in plastic viscosity.