Effect of Extrusion and Konjac Flour Addition on the Antioxidant Activity, Structural Properties, and In vitro Digestibility of Extruded Oat-Corn Flour

Oat-corn extruded powder is prepared to explore the effect of co-extrusion with konjac flour on the structural properties and functional properties of the mixed powder for a reduced starch digestion rate. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), antioxidant activity, and in vitro digestibility are applied for analysis. SEM images after extrusion treatment show irregularity of the surface with some cracks and grooves. XRD and FT-IR results show that the A-type crystal structure disappears after extrusion, and the in vitro digestibility is improved but not significantly (p > 0.05). After different amounts of konjac flour and oat and corn mixed powder are added for co-extrusion, the surface microstructure is relatively rough, the pores of the mixed system are reduced, the crystal form is V-shaped. The starch digestion rate is significantly decreased (p < 0.05). The mixed powder with the addition of 5-15% konjac flour is a low GI material. It can be used as a raw material for meal replacement products.