Dynamic Viscoelastic Behavior of Wheat Gluten: The Effects of Hydrogen Bonding Modification by Urea and Deuterium Oxide

Freeze‐dried wheat gluten was reconstituted with water, deuterium oxide, and 1M, 3M, and 5M aqueous solutions of urea. Differential scanning calorimetry and photoacoustic ultraviolet spectroscopy studies were conducted to obtain an independent assessment of the effects of these reagents. The storage and loss moduli of gluten reconstituted with water and deuterium oxide at the same frequency were higher for deuterated gluten. It was concluded that deuterium oxide does not cause conformational changes in gluten and that its main effect is a moderate increase in the strength of hydrogen bonding. For gluten reconstituted with urea, increasing urea concentration resulted in reduced frequency dependence of the storage modulus and a large decrease in the magnitude of the loss modulus, especially at the low frequencies. The increase in elasticity caused by urea was interpreted in terms of unfolding of the proteins upon disruption of hydrogen bonding. The interpretation of the rheological changes caused by urea and deuterium oxide is consistent with the results obtained by calorimetry and ultraviolet spectroscopy.