Cereal Chem 66:268-270   |  VIEW ARTICLE

Correlation Between the Glass-Transition Point and Color Change of Heat-Treated Gluten.

Y. Fujio and J.-K. Lim. Copyright 1989 by the American Association of Cereal Chemists, Inc. 

The color change and the density of heat-treated wheat gluten varies, depending on the treatment conditions. We studied heat treatment of gluten by comparing color changes in samples treated under various conditions. The change in color was dependent on the treatment temperature, up to a critical temperature specific to the sample. The critical temperature was significantly increased when the moisture content of the sample was reduced. For example, the critical temperature at 13% moisture was 30 C, whereas the critical temperature at 5% moisture was 100 C. Below the critical temperature, the degree of color change was found to be proportional to the treatment temperature. The density of heat-treated wheat gluten was proportional to the logarithm of the change in color. Based on differential scanning calorimetric measurement of wheat gluten at various moisture levels, it was confirmed that the critical temperature determined by the color change corresponded to the glass transition temperature of the sample. In fact, wheat gluten was transformed into a glassy material by the heat treatment, indicating the creation of noncrystalline (amorphous) molecular orientations.