Effects of twin‐screw extrusion processing variables on physicochemical properties and antioxidant activity of rice incorporated with Agriophyllum squarrosum flour

Agriophyllum squarrosum(L.) Moq (A. squarrosum) with high nutrition was first applied to food extrusion processing to produce rice powders. Response surface methodology (RSM) was used to investigate the effects of processing variables, namely the screw speed (90–130 rpm), moisture content (27%–39%), and extrusion temperature (100–160°C) on system parameters, physicochemical properties, and antioxidant activity of rice extrudates with A. squarrosum addition. Twin-screw extrusion cooking significantly (p < .05) improved the water absorption index (WAI), water solubility index (WSI), color index a* and b* of extruded products, and made the crystalline pattern of blends change from A-type to V-type. The extrusion temperature showed the most significant effect on system parameters, physicochemical properties, and antioxidant activity. These findings that indicated appropriate conditions of twin-screw extrusion to produce rice powders with A. squarrosum were 120 rpm screw speed, 31% moisture content, and 145°C extrusion temperature. The proximate composite of raw blend powder and extruded blend powder showed no evident changes except starch. Practical applications In this study, we mixed rice and Agriophyllum squarrosum flour to produce high nutritional blends and investigated the function properties by response surface methodology. On one hand, the regularity effects of extrusion on the total content of phenolic, flavonoid, and DPPH (2,2-diphenyl-1-picryhydrazyl) free radical scavenging activity were observed. On the other hand, we expanded the application of Agriophyllum squarrosum and provided a twin-screw extrusion method for the production of high protein cereal products.