Preparation of quinoa protein with ultrasound pretreatment and its effects on the physicochemical properties, structural and digestion characterizations

This study aimed to investigate the effects of ultrasound pretreatment on the yield and the physicochemical properties, structural and digestion characterizations of quinoa protein (QP). Results showed that under the conditions of ultrasonic power density of 0.64 W/mL, ultrasonication time of 33 min, and the liquid-solid ratio of 24 mL/g, the highest yield of QP at 68.403 % was obtained, which was significantly higher than that without ultrasound pretreatment at 51.26 ± 1.76 % (P < 0.05). Ultrasound pretreatment decreased the average particle size and ζ-potential but increased the hydrophobicity of QP (P < 0.05). However, no significant protein degradation and secondary structure changes of QP by ultrasound pretreatment were observed. In addition, ultrasound pretreatment slightly improved the in vitro digestibility of QP and reduced the dipeptidyl peptidase IV (DPP-IV) inhibitory activity of the hydrolysate of QP by in vitro digestion. Overall, this work demonstrates that ultrasound-assisted extraction is appropriate for improving the extraction efficiency of QP.