Extrusion Cooking of Corn Meal With Sodium Bicarbonate and Sodium Aluminum Phosphate

Sodium bicarbonate and sodium aluminum phosphate (0–0.45%) were mixed with corn meal and extruded in a twin-screw extruder at screw speeds of 200–400 rpm and initial moisture contents of 19.5–21.5% (wb). Increasing NaHCO3 and NaAl3H14(PO4)8 level increased product specific length and volume and decreased apparent bulk density and the expansion ratio. Increasing screw speed showed similar trends. An increase in initial moisture content decreased product specific length, specific volume and the expansion ratio and increased the bulk density. Product yellowness and lightness increased when the NaHCO3 and NaAl3H14(PO4)8 content was increased. Product cell size decreased and cell number increased when the NaHCO3 and NaAl3H14(PO4)8 level or screw speed was increased. Chemical analysis showed the amount of bicarbonate remaining in the finished product depended on the NaHCO3 and NaAl3H14(PO4)8 content. Product shear strength was not affected by the 3 and NaAl3H14(PO4)8 level.