THE GLASS-TRANSITION BEHAVIOR OF WHEAT GLUTEN PROTEINS

The glass-transition behaviour of four hydrated wheat gluten proteins (alpha-gliadin, gamma-gliadin, omega-gliadin and high-molecular weight (HMW) subunits of glutenin) was studied using differential scanning c alorimetry (DSC). By fitting the data to the Gordon-Taylor equation, w hich has previously been used to describe the plasticization of polyme rs by diluents, the glass-transition temperatures (T-g) for the dry pr oteins were found by extrapolation. The values for T-g were within the range 397-418 K. Values for the heat capacity increment Delta C-p at T-g for the plasticized proteins were also determined and ranged from 0.29-0.47 Jg(-1) K-1 with no dependence on water content. The differen ces in glass-transition behaviour of the proteins are discussed in rel ation to their secondary structure.