Determination of the thermo-mechanical properties in starch and starch/gluten systems at low moisture content – A comparison of DSC and TMA

Published Date
8 August 2014, Vol.108:1–9, doi:10.1016/j.carbpol.2014.02.049

Title 
Determination of the thermo-mechanical properties in starch and starch/gluten systems at low moisture content – A comparison of DSC and TMA

• Author 

• Stephen Homer ^,
• Michael Kelly 
• Li Day 

• CSIRO Animal, Food and Health Sciences, 671 Sneydes Road, Werribee, VIC 3030, Australia

Received 23 December 2013. Revised 13 February 2014. Accepted 15 February 2014. Available online 22 February 2014.

Highlights

• •
  Heating rate affects the temperature of transitions in starch as measured by DSC.
• •
  The optimum heating rate for starch T_g measurement by DSC was 5 °C/min.
• •
  T_g of starch changes upon ageing and is lowered by use of an initial heating scan.
• •
  Gluten plasticises starch and results in a lower T_g compared to starch alone.
• •
  TMA is a useful alternative to DSC for determining T_g in starch up to 80 °C.

Abstract

The impact of heating rate on the glass transition (T_g) 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 T_g 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 T_g while still being clearly observed above the baseline. T_g values determined from the first and second DSC scans were found to differ significantly and retrogradation of starch biopolymers may be responsible. T_gvalues of starch determined by TMA showed good agreement with DSC results where the T_g was below 80 °C. However, moisture loss led to inaccurate T_g determination 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
• T_g, glass transition temperature
• T_r, relaxation temperature

Keywords

• Starch
• Gluten
• DSC
• TMA
• Glass transition
• Heating rate

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• ⁎ 
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