Kinetics of Thermomechanical Destruction of Thiamin During Extrusion Cooking

Maize grits were extrusion cooked in a CM45-F conical, counter-rotating twin-screw extruder, at different barrel temperatures (140–200°C), feed moistures (11.8–14.2% w.b.), feed rates (37–51 kg/h), screw speeds (65–81 rpm), and initial thiamin concentrations (9–93 mg/kg). Residence time distribution was measured by a dye tracer technique. A first-order rate equation was used to model the reaction kinetics, which allowed the calculation of the destruction rate constant using residence time distribution curves. The k-values were most dependent on barrel temperature, feed moisture, and screw speed. The destruction rate constant of thiamin during extrusion cooking was a function of product temperature and shear stress.