Water sorption and dielectric relaxations of wheat dough (containing sucrose, NaCl, and their mixtures)

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 a, range of 0.225-0.753. Dynamic DEA measurements were made at a heating rate of 2degreesC/min from 40degreesC 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 a(w) range used for the plain dough (flour+water). Added ingredients increased sorption of doughs. The tan delta of DEA showed an alpha-relaxation (glass transition) in all doughs at all frequencies used. The relaxation peak temperature, taken as T-g, increased with increasing frequency. Added sucrose decreased the T-g of doughs, as well as added NaCl. A dramatic depressing effect of NaCl on T-g was probably due to an increase in conductivity of doughs. (C) 2003 Elsevier Science Ltd. All rights reserved.