Abstract: In order to study the effect of gelatinization by extrusion on physicochemical properties of tartary buckwheat flour, four different gelatinization degree of tartary buckwheat flour, 37.7%, 56.3%, 74.3% and 94.2%, were obtained by a single-screw extruder, and the major chemical constituents, pasting properties, hydration properties, thermodynamic properties and microstructure of the extruded flours were determined. The results showed that the contents of total flavonoids and lipids in flour reduced significantly (P < 0.05) and the color of flour became darker with the increase of gelatinization degree, while the contents of starch, ash and protein showed no significant change (P > 0.05). The proportion of damaged starch, water absorption index and water retaining capacity increased significantly (P < 0.05). The rapid viscosity analyzer analysis indicated that peak viscosity, trough viscosity, trough viscosity, final viscosity, setback, and peak time declined after extrusion. Scanning electron microscope observation showed that tartary buckwheat flour appeared as round or irregular polygon starch granules with smooth surface, while the extruded flour had no definite shape and the surface became rough with cracks and holes. To conclude, the above results provide useful data for insights into the underlying mechanism and for the application of extruded tartary buckwheat flour.

Key words: tartary buckwheat, extrusion, gelatinization degree, physicochemical properties