RHEOLOGICAL BEHAVIOR DURING EXTRUSION OF BLENDS OF MINCED FISH AND WHEAT-FLOUR

The effect of the extrusion process variables, such as length/diameter (L/D) ratio of the extruder, feed ratio (ratio of the solids of fish and wheat flour), temperature of extrusion, and screw speed on the rheological behaviour of blends of partially dried low-cost minced fish and wheat flour were studied. A single-screw, variable-length extrusion cooker, with a barrel bore of 25 mm was developed for this purpose. Pseudoplastic behaviour was observed during extrusion. The shear rate-shear stress data can be fitted (r greater-than-or-equal-to 0.93, p less-than-or-equal-to 0.01) to the power-law model. The L/D ratio of the extruder affects the rheological behaviour of the food dough during extrusion, and hence, the L/D ratio should also be considered as a process variable. A simple mathematical model to predict the rheological properties such as the consistency coefficient, flow behaviour index, and apparent viscosity of blends during extrusion, was proposed.