Rice Starch Isolation by Neutral Protease and High-intensity Ultrasound

The neutral protease and high-intensity ultrasound were combinedly used to isolate the rice starch,which viscosity was analyzed by Rapid Visco Analyzer(RVA).The results showed that the starch yield was 62.3%-73.8% with 3.74%-4.88% residual protein content by neutral protease alone,and 72.1%-77.2% with 0.68%-1.30% residual protein content by the combination of neutral protease and high-intensity ultrasound.Damaged starch content greatly decreased after sonication.The preferred combination was neutral protease digestion for 3 h followed by sonication at 50% amplitude for 40 min.The protease peak viscosity,setback viscosity and final viscosity of rice starch increased and breakdown viscosity of rice starch decreased after the combinations,which were the same to the alkaline treatment.This indicated that the high-intensity ultrasound produced no damage to starch properties.The combination of neutral protease and high intensity ultrasound was an effective technique for isolation of rice starch.