The glass-transition behaviour of wheat gluten proteins

The glass-transition behaviour of four hydrated wheat gluten proteins (α-gliadin, γ-gliadin, ω-gliadin and high-molecular-weight (HMW) subunits of glutenin) was studied using differential scanning calorimetry (DSC). By fitting the data to the Gordon-Taylor equation, which has previously been used to describe the plasticization of polymers by diluents, the glass-transition temperatures (T_g) for the dry proteins were found by extrapolation. The values for T_g were within the range 397-418 K. Values for the heat capacity increment ACp at T_g for the plasticized proteins were also determined and ranged from 0.29-0.47 J g^-1 K^-1 with no dependence on water content. The differences in glass-transition behaviour of the proteins are discussed in relation to their secondary structure.