Effect of operating conditions on melt rheological characteristics during twin-screw food extrusion

Data on operating (feed rate, feed moisture content, screw speed, and temperature) and process variables (product/barrel/die temperatures, zone 4-5/die pressures, total power consumption) of a co-rotating twin-screw food extruder, and extrudate moisture content were collected at 0.5 s intervals. The steady-state data were analyzed and the mean residence time and average apparent viscosity of melted cornmeal determined. The average apparent viscosity was calculated by using the total power consumption method and modeled as a function of the operating variables. The addition of two extra reverse paddles to the screw (configuration B) caused a decrease in fluid consistency coefficient (16.865 vs 20.130 kPas(n)) and an increase in shear-thinning behavior (0.22 vs 0.44) of the melt.

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