Optimization of Extrusion Process of Purple Brown Rice Flour and Its Physicochemical Properties

Using purple brown rice as raw material, the process parameters of twin-screw extrusion was studied buy the response surface method, and the changes of gelatinization characteristics, crystal characteristics and microstructure of purple brown rice flour before and after extrusion were characterized by RVA, XRD and SEM. Results showed that: The optimization of the extrusion process parameters about purple brown rice flour were extrusion temperature 147 ℃, moisture content 18%, screw speed 27 Hz and feed rate 18 Hz, the WSI of the sample was 11.32%, the gelatinization degree was 93.15%, the anthocyanin content was 97.38 mg/100 g, and the comprehensive scorse was 92.43. Under this extrusion condition, compared with the raw materials, the peak viscosity, lowest viscosity, attenuation value, final viscosity and retrogradation value of the extruded purple brown rice flour decreased significantly (P<0.05). The result showed that the starch crystal structure of extruded purple brown rice flour changed from A type to V type, and the crystallinity decreased. The surface of purple brown rice flour becomes smooth, showing more pore structure. The research showed that the use of extrusion technology could better improve the gelatinization properties and hydration characteristics of purple brown rice flour, and provide theoretical and technical parameter basis for the development of purple brown rice instant meal replacement flour products.