Water Sorption and Dielectric Relaxations of Wheat Dough (Containing Sucrose, NaCl, and their Mixtures) |
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| Authors: | T J Laaksonen Y H Roos |
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| Institution: | a University of Helsinki, Department of Food Technology, P.O. Box 27, (Latokartanonkaari 7), FI-00014 University of Helsinki, Helsinki, Finland;b University College, Cork, Department of Food Science and Technology, Cork, Ireland |
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| Abstract: | Dielectric relaxations of wheat doughs with different water contents and effects of sucrose, NaCl, and their mixture on relaxation temperatures were investigated using dielectric analysis (DEA). All ingredients were dissolved in distilled water used to prepare wheat flour doughs to optimum consistency. Before analysis, samples were stored at room temperature in vacuum desiccators over aw range of 0·225–0·753. Dynamic DEA measurements were made at a heating rate of 2 °C/min from 40 °C below and above the observed relaxation zone. The frequencies used were 0·1, 0·5, 1, and 5 Hz. Steady state water contents varied from 3·21 to 10·89 g H2O/100 g dm over aw range used for the plain dough (flour+water). Added ingredients increased sorption of doughs. The tan δ of DEA showed an α-relaxation (glass transition) in all doughs at all frequencies used. The relaxation peak temperature, taken as Tg, increased with increasing frequency. Added sucrose decreased the Tg of doughs, as well as added NaCl. A dramatic depressing effect of NaCl on Tg was probably due to an increase in conductivity of doughs. |
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| Keywords: | dielectric analysis (DEA) glass transition relaxation water sorption wheat dough |
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