in extrusion of corn meal of various particle sizes are presented in Table 3. The SEM is a good quantitative descriptor in extrusion processes and the amount of mechanical energy delivered to the extruded material determines the extent of macromolecular transformations and interactions that takes place, i.e. starch conversion, and consequently, the rheological properties of the melt. The calculated specific mechanical energy (SME) of corn meal extrusion ranged from 528 to 719 kJ/kg. These findings show that SME input was significantly affected by the particle average size (p < 0.05) and that increasing particle size decreased the SME input. Similar results were also reported by Altan et al. (2009) who showed the reduction in SME during extrusion of barley flour when compared to that of barley grits attribut- ing the influence of particle size on melt viscosity during the process. Large particles have less contact area both in relation to particle to particle and to the barrel and, consequently, are less affected by barrel temperature than finer particles as reported by Konstance and Onwulata (2006) and Desrumaux et al. (1998). The finer particles would heat more rapidly and reach the melt