Published Date
Received 23 December 2013, Revised 13 February 2014, Accepted 15 February 2014, Available online 22 February 2014.
Author
Highlights
Abstract
The impact of heating rate on the glass transition (Tg) and melting transitions observed by differential scanning calorimetry (DSC) on starch and a starch/gluten blend (80:20 ratio) at low moisture content was examined. The results were compared to those determined by thermo-mechanical analysis (TMA). Comparison with dynamic mechanical thermal analysis (DMTA) and phase transition analysis (PTA) is also discussed. Higher heating rates increased the determined Tg as well as the melting peak temperatures in both starch and the starch/gluten blend. A heating rate of 5 °C/min gave the most precise value of Tg while still being clearly observed above the baseline. Tg values determined from the first and second DSC scans were found to differ significantly and retrogradation of starch biopolymers may be responsible. Tg values of starch determined by TMA showed good agreement with DSC results where the Tg was below 80 °C. However, moisture loss led to inaccurate Tgdetermination for TMA analyses at temperatures above 80 °C.
For further details log on website :
http://www.sciencedirect.com/science/article/pii/S0144861714001775
Received 23 December 2013, Revised 13 February 2014, Accepted 15 February 2014, Available online 22 February 2014.
Author
- CSIRO Animal, Food and Health Sciences, 671 Sneydes Road, Werribee, VIC 3030, Australia
Highlights
- •
- Heating rate affects the temperature of transitions in starch as measured by DSC.
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- The optimum heating rate for starch Tg measurement by DSC was 5 °C/min.
- •
- Tg of starch changes upon ageing and is lowered by use of an initial heating scan.
- •
- Gluten plasticises starch and results in a lower Tg compared to starch alone.
- •
- TMA is a useful alternative to DSC for determining Tg in starch up to 80 °C.
The impact of heating rate on the glass transition (Tg) and melting transitions observed by differential scanning calorimetry (DSC) on starch and a starch/gluten blend (80:20 ratio) at low moisture content was examined. The results were compared to those determined by thermo-mechanical analysis (TMA). Comparison with dynamic mechanical thermal analysis (DMTA) and phase transition analysis (PTA) is also discussed. Higher heating rates increased the determined Tg as well as the melting peak temperatures in both starch and the starch/gluten blend. A heating rate of 5 °C/min gave the most precise value of Tg while still being clearly observed above the baseline. Tg values determined from the first and second DSC scans were found to differ significantly and retrogradation of starch biopolymers may be responsible. Tg values of starch determined by TMA showed good agreement with DSC results where the Tg was below 80 °C. However, moisture loss led to inaccurate Tgdetermination for TMA analyses at temperatures above 80 °C.
Abbreviations
DSC
differential scanning calorimetry
TMA
thermo-mechanical analysis
DMTA
dynamic mechanical thermal analysis
PTA
phase transition analysis
Tg
glass transition temperature
Tr
relaxation temperature
Keywords
Starch
Gluten
DSC
TMA
Glass transition
Heating rate
For further details log on website :
http://www.sciencedirect.com/science/article/pii/S0144861714001775
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