Physical properties of extruded corn grits with corn fibre by CO2 injection extrusion Original Research Article

Corn grits and corn fibre mixed at different ratios (0/100, 15/85 and 30/70) were extruded at different melt temperature (90, 105 and 120 °C) using extrusion with and without CO2 injection. Increasing melt temperature also significantly improved physical properties of extrudates in both non-CO2 and CO2 injection (200 mL/min) extrusion process. The injection of CO2 in the extrusion process showed similar effect on physical properties of extrudates at the lower melt temperature (90 and 105 °C), whereas it exhibited opposite trend at higher melt temperature (120 °C). At the lower melt temperature, the surface of extrudates with the CO2 injection was smoother and lower fracturability, and the cross sectional microstructure was more uniform. The addition of corn fibre decreased the expansion index, bulk density and breaking strength on the same extrusion condition. In addition, non-uniform and more broken cross-sectional microstructure was observed by the addition of corn fibre.