Effects of die dimensions on extruder performance

Yellow corn grits having 18% moisture content (dry basis) were extrusion cooked in a C. Ui Brabender single-screw laboratory extruder at 140 degrees C barrel temperature and 140 rpm screw speed. Die nozzle diameters ranged from 2 to 6.2 mm and die nozzle lengths ranged from 5.48 to 50.3 mm. Effects of die nozzle L/D on expansion propel-ties were dominated by die nozzle length or diameter separately, rather than by L/D. An increase in die nozzle diameter decreased radial expansion but it had no effect on overall expansion. An increase in die nozzle length increased overall expansion but had no effect on radial expansion. Further effects of die nozzle dimensions on operating pressure and specific mechanical energy also have been discussed. (C) 1997 Elsevier Science Limited.