TWIN-SCREW EXTRUSION OF RICE FLOUR WITHOUT A DIE - EFFECT OF BARREL TEMPERATURE AND SCREW SPEED ON EXTRUSION AND EXTRUDATE CHARACTERISTICS

Rice flour with 14% moisture content was extruded at different barrel temperatures (80-120 degrees C) and screw speeds (200-400 rpm) through a twin-screw extruder without a die. The system parameters as well as the extrudate attributes were mainly dependent on temperature, wherea s the screw speed imparted a lesser effect. Optimum extrusion conditio ns for obtaining minimum torque, specific mechanical energy (SME) and bulk density were determined. A positive linear (correlation coefficie nt r = 0.78, significant at a probability level p less than or equal t o 0.01) relationship existed between SME and bulk density indicating t hat low-density extrudate is possible to obtain with low SME. Extrusio n of rice flour without a die appears to be an alternative approach to produce processed rice flours with high water absorption index and in vitro starch digestibility. (C) 1997 Elsevier Science Limited.