Glass Transition Temperatures Determined using a Temperature-Cycling Differential Scanning Calorimeter

Authors


  • This research was funded through the Alabama Agricultural Experiment Station, Auburn University, AL 36489 and is AAES Journal No. 10–955078.

ABSTRACT

Glass transition temperatures, Tg, 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°C/min with an amplitude of ± 1°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 Tg of complex food systems at low moisture contents, glass transitions were observed for solutions and food systems at higher moisture contents. Tg values from MDSC were reproducible and similar to those from standard DSC.

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