Preparation Of ACE Inhibition Peptide From Rice Protein With Utrasound-Assisted Enzymolysis

Rice protein, as a high-quality protein resource, has huge yield every year. Because of the limited industrialized process, it is not well utilized. The objectives of this study were to prepare ACE inhibitory peptide from rice protein by ultrasound-assisted enzymolysis, evaluate the properties of ACE inhibitory peptide, and describe the mechanism of ultrasound-assisted enzymolysis. The main results are shown as follows:Alcalase was the best enzyme, selected from four commercial enzymes.Based on the singular results, the substrate concentration, enzyme concentration and pH were studied for orthotropic tests.The determined optimum condition was substrate concentration of 4%,enzyme concentration of 7.5%(E/S), pH value of 9.5,temperature of 50℃and time of 40min. Under the optimum condition, the ACE inhibitory rate was 75.1%.This research studied the effect of ult asound treatment on the enzymolysis preparation of ACE inhibitory peptide from rice protein and its mechanism. The optimum condition of ultrasound-assisted enzymolysis was ultrasonic power of 250W/L, time of 10min, on-time to off-time ratio of 1:2 and rotating speed of 30r/s. Under the optimum condition, the ACE inhibitory rate of hydrolysate was increased from 75.1% to 92.8% obtained from the control without ultrasound treatment. The analytical results showed that the fluorescence spectrum of hydrolysate was changed much by the ultrasound treatment and the solubility of rice was also increased greatly.The ultrafiltration results showed that 5k Da is the optimum molecular weight cut-off. After ultrafiltration with 5k Da mebrance,IC50 value of ultrafiltrate was decreased to 1.71mg/ml,which meant that ACE inhibitory rate was increased much by the ultrasound treatment. The rice antihypertensive peptide has good capability of fighting degradation against digestive enzymes and high antihypertensive capability for SHR mice.The research also studied the effect of ultrasound treatment on the activity and free sulfhydryl content of alcalase.The alcalase activity was increased by 3.12% and the increase in alcalase activity was the highest at the ultrasonic power of 750W/L. The free sulfhydryl content of alcalase was increased by 5.6% and its increase was the highest at the ultrasonic power of 1000W/L. In general, the ultrasound treatment has a prominent effect on the enzymolysis preparation of ACE inhibitory peptide from rice protein by alcalase.