Investigation of fat bloom mechanism in dark chocolate

The effect of shear and cooling rates on the crystallization of cocoa butter has been studied using a differential scanning calorimeter (DSC), X-ray diffraction (XRD) and a rheometer. Three different shear rates (25, 50 and 100 s-1) and two different cooling rates (1 and 10 ºC/min) were tested at 20, 22 and 24ºC. Different polymorphic forms of cocoa butter were produced and identified. Dark plain chocolates were produced in six different compositions and three different temper indexes. Fat bloom was accelerated by repeated two different temperature cycles (20±0.5ºC - 32±0.5ºC and 16±0.5ºC - 32±0.5ºC) using controlled temperature humidity chambers for 3 weeks. Ideally tempered dark chocolate were stored for one year at 10, 18, 22 and 24°C to determine the effect of storage temperature on fat bloom formation. Polymorphic transformations in chocolates were followed by using XRD, DSC and macroscope. Also, textural and image analysis were done at different time intervals. Effect of cooling rate on crystallization of cocoa butter was more significant at low temperatures (p < 0.05). Fast cooling rates caused decrease in viscosity change of cocoa butter. The formation of fat bloom was mostly prevented by storage at low temperatures. Rate of fat bloom development in chocolates was dependent on the composition, temper index value, storage temperature and time. The initial properties of chocolates cycling between 16 - 32ºC changed greater than other chocolates. The rate of fat bloom formation was the highest for chocolates tempered incorrectly.