Physicochemical and antioxidant properties of extruded corn grits with corn fiber by CO2 injection extrusion process

• The CO2 injection increased water absorption index.
• The addition of corn fiber significantly increased antioxidant properties.
• Increasing corn fiber content helped retain total phenolic content during extrusion.
• Color and antioxidant properties stable in CO2 injection extrusion at 120 °C.

Corn grits and corn fiber mixed at different mass 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. The L value, reducing sugar content and antioxidant properties decreased after extrusion with or without CO2 injection. The color and antioxidant properties were relatively stable in the extrusion with CO2 injection at higher melt temperature (120 °C) in comparison with the extrusion without CO2 injection. Higher corn fiber content resulted in less loss of total phenolic content. The b, ΔE values and water absorption index increased after extrusion. The increase of the water absorption index was higher after the extrusion process with the CO2 injection especially at the lower melt temperature. The addition of corn fiber decreased L, b, and ΔE values, but significantly increased antioxidant properties under the same extrusion conditions.