Thermal properties of corn gluten meal and its proteic components |
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Authors: | Lodovico Di Gioia Bernard Cuq Stphane Guilbert |
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Institution: | Unité de Technologie des Céréales et des Agro-polymères, ENSA.M/INRA, 2 Place Viala, 34060 Montpellier Cedex 1, France |
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Abstract: | Thermal properties of corn gluten meal (CGM) and of its extracted proteic components (zein and glutelin) at 0% moisture content, is studied by dynamic mechanical thermal analysis (DMTA) and modulated differential scanning calorimetry (MDSC). The glass transition temperature (Tg) on first heating, is measured at 176 and 174°C, respectively, for hot-air-dried and native CGM. For zein and glutelin isolated fractions, the measured Tg values are 164 and 209°C, respectively. The calculated Tg from using Matveev’s method (Matveev YI. Spec Publ R Soc Chem 1995;156;552) is in good agreement with experimental data for zein, a well defined protein. MDSC allows the measurement of change in heat capacity at Tg (ΔCp) with a single heating scan, avoiding sample alteration, and ΔCp values are 0.365 J/g per K for zein and 0.184 J/g per K for glutelin. The differences observed in Tg, relaxation temperatures, ΔCp and tan δ peak height are related to differences in the structure of the proteins, through the cross-linkages and hydrogen or van der Waals interactions. Experimental data from DMTA and MDSC, and the Couchman–Karasz thermodynamic approach indicate that CGM behaves as a miscible blend of its components, with high non-polar interactions between zein and glutelin proteins. |
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Keywords: | protein analysis gluten zein glutenin polymer |
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