EXPANSION CHARACTERISTICS OF EXTRUDED CORN GRITS

Yellow corn grits with 180 g/kg moisture content (dry basis) were extr usion cooked in a Brabender single-screw laboratory scale extruder wit h various combinations of barrel temperature (100-200 degrees C) and s crew speed (80-200 rpm). Bulk densities, solid densities, expansion pr operties, and total, open and closed pore volumes were determined. Ext rudate bulk density, measured by glass bead displacement, was highly c orrelated with the bulk density based on the actual dimensions of the extrudates. Overall and radial expansion increased with temperature an d screw speed whereas axial expansion decreased. Axial expansion was a ffected mostly by surging. The pore volumes had an increasing trend wi th temperature and screw speed.