Glass transition temperatures determined using a temperature-cycling differential scanning calorimeter

Glass transition temperatures, T-g, of polystyrene, polyvinylpyrrolidone, polydextrose, gelatin, corn flakes, pasta, and aqueous glucose/glycine solutions were determined using a differential scanning calorimeter which cycled the temperature while the net temperature increased at a constant rate. Operating conditions of the modulated differential scanning calorimeter(TM) (MDSC(TM)) for optimizing the endothermic baseline shift associated with the glass transition were a scan rate of 5 degrees C/min with an amplitude of +/- 1 degrees C over a modulation period of 60 or 100 sec. The MDSC successfully separated the glass transition from other irreversible thermal changes in simple food ingredients. While the MDSC did not distinctly determine T-g of complex food systems at low moisture contents, glass transitions were observed for solutions and food systems at higher moisture contents. T-g values from MDSC were reproducible and similar to those from standard DSC.