| The rheological properties of three different cooked corn meal doughs were determined by three different methods (squeezing flow, steady shear, and dynamic shear). Squeezing flow viscometry is the method to detect the variation between corn meal samples. Under biaxial extension, the cooked corn meal dough could be described as a power-law fluid and exhibited a strain thinning behavior, as the flow passed the transient regime. The normal stress difference of cooked corn meal dough could be modeled as a function of moisture content and biaxial strain rate, with a flow behavior index, n, of 0.41-0.47 and consistency coefficient, K, ranging from ;The operating variables (feed rate, feed moisture content, screw speed, and temperature), process variables (product/barrel/die temperatures, zone 4-5/die pressures, power consumption), extrudate moisture content, and color index of a twin-screw food extruder were collected at 0.5 second intervals by two data acquisition systems. The steady-state data were analyzed and mean residence time and average apparent viscosity of melted corn meal were determined.;The relationship between operating variables and product quality attributes (PQA) (bulk density, color b index, moisture content of extrudates) was modeled using multiple linear regression. Results indicated that the regression coefficients of the model became smaller, when one more reverse kneading paddle was added to the shear section of the extruder. This reveals that PQA is less sensitive to the change in operating variables.;The average apparent viscosity of melted corn meal was calculated by using the total mechanical energy consumption method and modeled as a function of operating variables. The average apparent viscosity decreased and the fluid became more shear thinning (0.54 vs 0.44) after one extra reverse paddle was added to the screw configuration. |
