Journal of Cereal Science 37 (2003) 319–326 doi:10.1006/jcrs.2002.0506 Water Sorption and Dielectric Relaxations of Wheat Dough (Containing Sucrose, NaCl, and their Mixtures) T. J. Laaksonen*² and Y. H. Roos‡ ²University of Helsinki, Department of Food Technology, P.O. Box 27 (Latokartanonkaari 7), FI-00014 University of Helsinki, Helsinki, Finland; ‡University College, Cork, Department of Food Science and Technology, Cork, Ireland Received 13 March 2002 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 a w 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89g H 2 O/100 g dm over a w range used for the plain dough (flour  water). Added ingredients increased sorption of doughs. The tan d of DEA showed an a-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. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: dielectric analysis (DEA), glass transition, relaxation, water sorption, wheat dough. INTRODUCTION One of the most common techniques in determining the phase and state transitions of various cereal materials is differential scanning calorimetry (DSC) 1–12 . Baked products often show a broad glass transition with a small change in heat capacity. Therefore, it has been concluded 8,9,11 that DSC, as used in those studies, is not sensitive enough to observe state transitions, such as glass transition, in wheat doughs. Other more sensitive techniques have been used to measure phase and state transitions of cereal foods, such as dynamic-mechanical (thermal) analysis (DMA/DMTA) or dielectric (thermal) analysis (DEA/DETA) 3,8,9,11,13–20 . According to Wetton 21 and Rotter and Ishida 22 DMA/DMTA is about 1000 times more sensitive in observing thermal transitions than DSC. Moreover, we have previously shown that dielectric analysis is even more sensitive in observing the phase and state transitions in wheat doughs than is DMA 8,9,11,19 . In our previous study 20 , DMTA was used to measure the effects of moisture on relaxations in wheat doughs with added ingredients. DMA/DMTA and DEA/DETA differ in how they measure relaxations occurring in poly- mers. DMA/DMTA measures three major proper- ties of material: (1) the storage modulus, G 0 , which is a measure of the amount of energy stored in the material per cycle; (2) the loss modulus, G 00 , which is proportional to the amount of energy dissipated per cycle; and (3) the loss tan d, which corresponds to the ratio of energy lost to the energy stored per cycle, as a function of time, frequency, and temperature. By 0733–5210/03/030319  08 $35.00/0 # 2003 Elsevier Science Ltd. All rights reserved.  Corresponding Author. E-mail: tommi.laaksonen@helsinki.fi