Relaxations below glass transition temperature in bread and its components

Dry glassy bread, cooked gluten, and gelatinized wheat starch-sucrose mixtu res were prepared. Dielectric properties were studied as a function of temp erature at different frequencies ranging from 100 to 1,000 kHz. Both bread and starch samples exhibited a tan delta peak at -53 degrees C at 10 kHz, w hich is associated with a secondary relaxation characterized by an activati on energy of 50 kJ/mol. The gluten sample did not show any relaxation in th e temperature range studied. The magnitude of the relaxation peak was sensi tive to the sucrose concentration of the starch sample. The higher the sucr ose content, the greater the amplitude of the peak. Such an effect is attri buted to a greater beta-relaxation induced by an increasing number of relax ing units or increasing size of the loosely packed regions of the glass. Ho wever, it cannot be concluded whether the relaxation is associated with a g roup present on both starch and sucrose or that the sucrose has an enhancin g effect on starch mobility.