New plasticizers for wheat gluten films

Diethanolamine and triethanolamine were selected among several low and high molecular weight polyols and amines tested as potential plasticizers of wheat gluten film. In comparison with glycerol, their use did not significantly affect the solubility in water, the opacity of the film (both increased very slightly) and the water vapor barrier properties. However, significant changes in mechanical properties were observed, i.e., increase in extensibility and elasticity. At 58% relative humidity (RH) and 20 g/100 g dry matter of di or triethanolamine, the elongation was five times higher than film plasticized with glycerol. At 98% RH, water appeared to compete with the amines to act as the plasticizer. Dynamic mechanical thermal analyses showed a glass transition temperature similar to that of the glycerol plasticized film. However, the observed broadening of thermal transition and the decrease in height of tan δ peak in the presence of amines, were related to differences in the type of the interactions with the proteins and to the basicity of the amino compounds.