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°C to 180°C, residence times of 2–60 set and shear rates of 10–275 sec ‐l . Polyrnerization 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 kcaVmo1 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.