Optimization of extrusion cooking of corn meal as raw material for bakery products

The objective of this work was the optimization of extrusion process for the production of extruded corn meal that may be used in the production of corn bread by a direct procedure. The extrusion process variables, barrel temperature, Et (111-159 oC), moisture content, Mc (12.10 - 24.77 %) and screw speed, Ss (160-460 rpm) were considered and their influence on moisture content (Mc), Expansion Index (EI), bulk density (BD), Water Solubility Index (WSI), Water Absorption Index (WAI) and Cold Paste Viscosity (CPV) of extrudates was investigated. The influence of extruded corn meal addition on viscosity of wheat flour and corn meal mixture was monitored. The optimimum combination of extrusion conditions was Mc=21.21% / Et=145oC / Ss=263.5 rpm. The properties of extruded corn meal under optimal extrusion conditions were: Mc, 10.97 % ; EI, 4.22 ; WAI, 7.84 g gel/g dm ; WSI, 14.88 % ; BD, 36.35 g/100mL and CPV, 1220 BU. In the quantity of 30 % calculated on the wheat flour quantity, the extruded corn meal can be used for the production of corn breads by a direct procedure.