TWIN-SCREW EXTRUSION OF RICE FLOUR WITH SALT AND SUGAR

The effects of screw speed, salt (0-3%), and sugar (0-8%) contents on the extrusion of rice flour using a corotating, fully intermeshing twi n-screw extruder were studied. Increasing the screw speed, salt, or su gar generally decreased the torque and die pressure. The screw speed w as a more important determinant of the three processing variables (tor que, specific mechanical energy, and die pressure) than was the salt o r sugar content. The extrudate diameters (radial expansion) were affec ted only by the sugar content, not by the salt content or screw speed. The extrudate lengths (axial expansion) were higher at a screw speed of 300 rpm than at 200 rpm; they also increased with the salt and suga r. Significant increases in the specific volume were found with the ad dition of salt and sugar and an increase in screw speed. The breaking strength of extrudates was inversely related to the radial expansion. Raising the screw speed from 200 to 300 rpm resulted in whiter, less g reen extrudates.