GLASS TRANSITIONS IN STARCH, GLUTEN AND BREAD AS MEASURED - DIELECTRIC-SPECTROSCOPY AND TMA METHODS

Dielectric Spectroscopy (DS) and Thermomechanical Analysis (TMA) were used to identity the glass transition temperature (T-g) of native whea t starch, vital wheat gluten and a commercial bread, in response to ch anges in moisture content. An open-ended coaxial probe technique was u sed to measure the permittivity or dielectric constant (epsilon') and the loss factor (epsilon '') as functions of moisture, for 2.45 GHz fr equency, at constant density and temperature. plots of epsilon' and ep silon '' as functions of moisture content showed dramatic changes in m obility-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 around T-g. This stu dy further confirms that synthetic polymer science principles can be a pplied to food systems.