|Bietz, Jerold - NCAUR (RETIRED)|
|Wirtz, Denis - JOHNS HOPKINS UNIV|
Submitted to: International Congress on Rheology
Publication Type: Abstract Only
Publication Acceptance Date: August 25, 2000
Publication Date: N/A
Technical Abstract: The linear rheological properties of vital wheat gluten solutions were studied using a strain-controlled rheometer. A series of concentrations of gluten solutions were investigated. The plateau moduli strongly depend on the gluten solution concentration. The storage modulus varied from 1.8 dyne/cm**2 for a 225 mg/ml gluten solution to about 350 dyne/cm**2 for a 325 mg/ml gluten solution. The plateau moduli exhibit a sharp increase between 250 mg/ml and 300 mg/ml. Below 250 mg/ml, the material shows more fluid-like properties. The phase shifts vary from 23 deg at a frequency of 0.001 rad/sec to 65 deg for at 100 rad/sec. The G' and G" crossover frequency is shifted slightly from 0.5 rad/sec for a 225 mg/ml gluten solution to 0.9 rad/sec for a 250 mg/ml gluten solution. However, above 300 mg/ml, the material exhibits solid-like behavior. The phase shifts vary from 23 deg at 0.001 rad/sec to 45 deg at 100 rad/sec. The G' and G" crossover frequencies are all close to 100 rad/sec. The behavior of high-frequency moduli of gluten solutions below 250 mg/ml is totally distinct from the behavior above 300 mg/ml. Below 250 mg/ml, the high-frequency moduli are proportional to w**3/4, which indicates that the material exhibits semi-flexible chain behavior. Above 300 mg/ml, the high-frequency moduli are proportional to w**1/2, which denotes flexible polymer behavior. These results suggest that vital wheat gluten solutions undergo a structure change between 250 mg/ml and 300 mg/ml.