Glass transition temperatures determined via temperature-fluctuating differential scanning calorimetry

摘要

The determination of the glass transition temperature (T_g) has become important due to its ability to explain physical changes that occur in foods. However, the T_g may be hidden by other thermal events occurring simultaneously. Temperature-fluctuating DSC, where the temperature cycles while the net temperature increases at a constant rate, is supposed to separate reversible thermal phenomena (e.g., T_g) from irreversible thermal phenomena. Using temperature-fluctuating DSC, the T_g was successfully separated from irreversible thermal phenomena in simple food ingredients. While the glass transition of more complex food systems at low moisture contents was difficult to detect, glass transitions were observed for solutions and food systems at higher moisture contents. Reversible glass transitions were differentiated from other irreversible endothermic baseline shifts, which could be mistaken for the T_g. Temperature-fluctuating DSC is useful for food scientists who need to determine T_g values. However, experience has indicated that temperature-fluctuating DSC is not a replacement for standard DSC or other types of thermal analyzers, but should be used as a complimentary method.