Structural modification of quinoa seed protein isolates (QPIs) by variable time sonification for improving its physicochemical and functional characteristics.

High intensity ultrasound treatment (HIUS) by probe method is a novel technique to impart desirable physical, structural and functional characteristics to the native proteins structures. In this concern, effect of HIUS treatment at variable intervals from 5 to 35 min on quinoa seed protein isolates (QPIs) characteristics was analyzed. A typical dynamic rheological characteristic curve of QPIs had been obtained as a result of HIUS treatments at variable time intervals. Higher sonication resulted in the formation of large protein aggregates with higher particle size which increased QPIs turbidity. Temperature and frequency sweep tests had shown dominance of storage modulus over loss modulus, thus described strong gelling behavior of treated QPIs. HIUS treatment reduced particle size of QPIs with improved its flow properties. No splitting of bands had occurred due to sonication, whereas, more intensity of bands of treated QPIs depicted its greater water solubility. HIUS treatment decreased fluorescence intensity of QPIs whereas, no significant changes in Amide-II & III regions of QPIs occurred except decrease in wave number. The effects of HIUS on QIPs isolates had shown completely different response than those of results of quinoa protein extracts. Moreover, the studies conducted on quinoa protein extracts provided detailed information about the effect of HIUS on structural changes and its impact on physicochemical, functional and rheological characteristics.