Development of a rheometer-based new method for the determinatıon of chocolate pre-crystallization kinetics and the formulation of polymorf types

The tempering process, which has a direct effect on the quality of chocolate, is extremely important in terms of melting, resistance to fat bloom, textural, brightness and sensory properties. However, existing methods are insufficient to determine the polymorph types formed during the tempering process. Within the scope of the thesis, a novel rheometer-based method was developed to determine the polymorph type formed in chocolate; The experiments were carried out in two main steps in order to determine the amounts and melting points of polymorphic crystals by rheometer. Moreover, kinetic modeling was carried out for each crystallization concept by Gompertz sigmoidal equation with 4 unknowns. Within the scope of the thesis study, the effects of process (strain and temperature applications) and composition (cocoa butter alternatives, differences in milk, dark and white chocolate compositions) based variables were studied along with method development. Additionally, the effect of βv concentration and temperature on the pre-crystallization behavior for the seeding process, where the conventional tempering process was not applied, was examined. An attempt was made to establish a correlation between the results obtained from the rheometer and the results obtained from the polarized light microscope. As a result, a method that allows the determination of crystallization formation and melting points has been developed, going beyond the main purpose of the rheometer device, which is to determine the flow behavior of materials. According to the results obtained, the conditions that allow the formation of the highest amount of βv polymorphic crystals for cocoa butter are; It is 1% strain applied at 26oC and 28oC. For crystallization conditions in chocolate compositions, 22°C for white chocolate, 24°C for dark chocolate, and 28°C for milk chocolate with 0.1% strain.