Technology for twice extrusion of instant rice with twin-screw extruder

A central composite rotatable design was adopted to analyze the effects of cooking temperature, moisture content and screw rotating speed on degree of rehydration ratio, and the quadratic regression model of rehydration was deduced. Then a response surface method was employed to obtain the following optimal parameters: cooking temperature was 120℃, material moisture content was 33%, and screw rotating speed was 200 r/min. The rehydration characteristics of the instant rice produced in this condition is good. After rehydration in boiled water for 3min, the rehydration ratio was up to 285% and the hardness and elasticity were similar to those of fresh hybrid rice.