Characterisation of glass transition of durum wheat semolina using modulated differential scanning calorimetry
2001
Cuq, B. | Icard-Verniere, C.
The glass transition of wheat durum semolina was characterised at different moisture contents using modulated differential scanning calorimetry. The total, reversing and non-reversing heat flows were quantified during heating, cooling and re-heating. An endothermic peak was observed on the non-reversing heat flow during first heating and was not greatly affected by changes in moisture content (below 20 g water/100 g dry matter). This peak was associated with endothermic relaxation of the protein fraction in wheat semolina. An endothermic baseline shift was observed on the reversing heat flow during first heating, cooling and re-heating. The temperature at baseline shift decreased (from 110 degrees C to 27 degrees C) when moisture content increased (from 6% to 27% db). The measured heat capacity change (0.10-0.25)J/g/degrees C) was not significantly affected by moisture content. This endothermic baseline shift was presumed to be the glass transition of amorphous polymers in wheat durum semolina. The plasticising effect of water on the glass transition temperature (Tg) was described using Gordon Taylor and Kwei models and compared with Tg of the main wheat components.
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