Variability of melting behavior of commercial granulated sugar measured by differential scanning calorimetry

The melting point and endothermic curve analyzed by differential scanning calorimetry (DSC) of commercial granulated sugars were different according to the maker. Three endothermic peaks occurred at around 153°C, 160°C and 172°C, when the sucrose crystal (grain size between 100 and 200 mesh) recrystallized in purified water sucrose solution was analyzed at a heating rate of 10°C/min by DSC. However, when the sucrose crystal recrystallized in sucrose solution containing potassium chloride (KCl) as impurity, the two endothermic peaks at around 153°C and 160°C diminished and the endothermic peak around 172°C intensified and shifted to a region of higher temperature, and the melting point was higher. Furthermore, when the sucrose crystal recrystallized in raw sugar solution, only one endothermic peak appeared at more higher temperature and the melting point was the highest. It is clear that a very small amount of impurities in fine liquor in sugar refinery causes the difference of the melting point of prepared sucrose crystal (commercial granulated sugar).