POLYMERIZATION AND MECHANICAL DEGRADATION KINETICS OF GLUTEN AND GLUTENIN AT EXTRUDER MELT-SECTION TEMPERATURES AND SHEAR RATES

Thermal polymerization and mechanical degradation rates were measured for wheat gluten and glutenin at 25-30% moisture. Changes in soluble protein and disulfide bonds were measured at 85 degrees C to 180 degrees C, residence times of 2-60 sec and shear rates of 10-275 sec(-1). Polymerization rates without shear were evaluated using isothermal analysis. An extrusion rheometer was used to simulate extruder conditions to determine the combined polymerization-degradation rates. Molecular weight distributions of soluble reaction products were determined using liquid size exclusion chromatography. Activation energies were 0.60-2.1 kcal/mol, 2.0-8.2 kcal/mol, and 0.50-0.90 kcal/mol and reaction orders were 0.5-2.0, 0.8-1.5, and 0.6-0.7, respectively for polymerization without shear, polymerization with shear, and degradation.