Cereal Chem. 70:471-475   |  VIEW ARTICLE

Thermal Behavior of Annealed Acetic Acid-Soluble Wheat Gluten.

J. W. Lawton and Y. V. Wu. Copyright 1993 by the American Association of Cereal Chemists, Inc. 

The effect of annealing acetic acid-soluble wheat gluten at temperatures below its glass transition temperature (Tg) was investigated using differential scanning calorimetry (DSC). Acetic acid-soluble wheat gluten was annealed at 10 C below its Tg for various lengths of time. Subsequent DSC of the annealed gluten revealed an endothermic peak near its Tg. The area of this peak, which depended both on the time annealed and the DSC heating rate, appears to be associated with the relaxation of glassy gluten toward a lower energy state and can be explained by retardation kinetics. Thus, there is no need to invoke first-order thermodynamic processes to explain the energy absorption of amorphous gluten observed in the DSC after annealing. The calorimetric data obtained with isolated gluten fit a theory of enthalpy relaxation used to explain endothermic peaks in amorphous synthetic polymers. Energy absorption and peak temperature from the thermogram can be used to estimate the relaxation rate and activation energy for enthalpy relaxation.