The Melting and Glass Transitions of Carbohydrates by Advanced Thermal Analysis

摘要

The quantitative thermal analysis of crystalline and amorphous carbohydrates such as α-Dglucose, D(-)fructose and sucrose is presented utilizing standard differential scanning calorimetry (DSC) and quasi-isothermal temperature-modulated differential scanning calorimetry (TMDSC). The total apparent and reversing heat capacities of carbohydrates were evaluated on heating and cooling. The results were compared for the melting process of crystal and the glass transition region of an amorphous α-D-glucose, D(-)fructose and sucrose, respectively. The melting temperature shows heating rate dependency with superheating of around 30 K. The stability of carbohydrates was measured by thermogravimetric analysis (TGA) and quasi-isothermal method of TMDSC in the melting region. Results show changes of mass and in the reversing heat capacities with temperature and time, respectively. The experimental heat capacity of α-D-glucose, D(-)fructose and sucrose was analyzed in reference to the solid, vibrational, and liquid heat capacities of carbohydrates which were approximated based on the ATHAS scheme and Data Bank.