Effect of hydrophilic plasticizers on thermomechanical properties of corn gluten meal

The glass transition temperature and rheological moduli of plasticized corn gluten meal (CGM) were determined with dynamic mechanical thermal analysis (DMTA). The tested plasticizers were water, glycerol, polyethylene glycols (PEG) 300 and 600, glucose, urea, diethanolamine, and triethanolamine, at concentrations of 10-30% (dwb). The glass transition temperature (T-g) Of CGM, measured at 188 degrees C when unplasticized, was lowered by >100 degrees C at 30% plasticizer content, except by PEG 600 and glucose, which showed limited compatibility with CGM proteins. The highest plasticizing efficiency, on a molar basis, was measured with PEG 300 and was attributed to the large number of hydrophilic groups and the high miscibility of this compound with CGM proteins. The change in T-g due to the plasticizing effect was modeled with the Gordon and Taylor equation, but a better fit of the experimental data was obtained with the Kwei equation.