Journal of Food Engineering, Vol.32, No.3, 251-267, 1997
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, whereas the screw speed imparted a lesser effect. Optimum extrusion conditions for obtaining minimum torque, specific mechanical energy (SME) and bulk density were determined. A positive linear (correlation coefficient r = 0.78, significant at a probability level p less than or equal to 0.01) relationship existed between SME and bulk density indicating that low-density extrudate is possible to obtain with low SME. Extrusion 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.