WATER-VAPOR SORPTION BEHAVIOR OF ORIGINAL AND DEFATTED WHEAT GLUTEN

The water vapour sorption isotherms of original and defatted gluten sa mples, prepared from two wheat cultivars (Spring and Taurus) with good and poor baking performance, respectively, were investigated at 25 an d 40 degrees C. The GAB isotherm equation described the isotherms well up to a relative humidity of at least 84% at 25 degrees C and up to 7 5% at 40 degrees C. The GAB constants of Spring gluten indicated an in creased number of adsorption sites and a decreased average interaction energy per binding site at increased defatting (petroleum ether, chlo roform). This tendency was also observed for Taurus, however, here no significant differences were found between the solvents. When comparin g both cultivars the isotherm analysis indicated less available active sites for water adsorption with a stronger interaction energy per sit e for Taurus gluten. This stronger interaction is in accord with the h igher isosteric heat of adsorption (Clausius-Clapeyron analysis) found at low relative humidities. These findings are related to bread bakin g performance.