Changes in Viscosity during Crystallization Processes of Cocoa Butter and Chocolate

Changes in viscosity of cocoa butter and chocolate during crystallization processes were measured by a rotational viscometer which was newly equipped in the present study. This viscometer facilitates a computerized tempering with agitation of the sample, yielding a torque of sample. The tempering process was a simple cooling of melt (60°C) to several crystallization temperatures. It was confirmed that the torque was linearly proportional to viscosity values obtained by Brookfield type viscometer. The viscosity changed through three different stages : First, the constant viscosity was attained after the crystallization temperature was reached. Second, the viscosity gradually increased due to early nucleation and crystal growth of solid fats. Third, a sharp increase of viscosity was caused by accelerated crystallization. The amount of crystallized fats in chocolate during the industrial-used tempering machine (60-27-30°C) was estimated about 0.17%, based on the viscosity changes examined by the present method.