Glass transitions in starch,gluten and bread as measured

Dielectric Spectroscopy (DS) and Thermomechanical Analysis (TMA) were used to identity the glass transition temperature (T _g) of native wheat starch, vital wheat gluten and a commercial bread, in response to changes in moisture content. An open-ended coaxial probe technique was used to measure the permittivity or dielectric constant (?′) and the loss factor (?″) as functions of moisture, for 2.45 GHz frequency, at constant density and temperature. Plots of ?′ and ?″ as functions of moisture content showed dramatic changes in mobility-based dielectric properties, which occur upon transition from the glassy solid to the rubbery liquid state. The modified TMA method can measure the change in viscoelastic properties aroundT _g. This study further confirms that synthetic polymer science principles can be applied to food systems.