Effect of Ultrasound Treatment on Particle Size Distribution and Protein Composition of Soy Protein Isolate & Concentrate Suspensions

Humans can hear the sound which has the frequencies in the range of 20 Hz-20 kHz. Ultrasound is the sound whose frequency is too high for humans to hear, i.e., the frequency of ultrasound is above 20 kHz. In this work both low-intensity ultrasound (40 and 500 kHz) and the high-intensity ultrasound (20 kHz probe) were used. 10 % (on dry matter) protein model suspensions of soy protein isolate (SPI) and soy protein concentrate (SPC) were treated with ultrasound probe (20 kHz for 15 and 30 minutes) and ultrasound baths (40 and 500 kHz for 15 and 30 minutes). 1 The aim of this study was to observe the effect of ultrasound and sonication on particle size distribution and, protein composition of soy proteins. Effect of ultrasound treatment on pH and temperature changes during treatments was also observed. The protein fractions were analyzed by SDS-PAGE electrophoresis, and particle size was determined by laser light scattering using a Mie scattering model. The particle size reduction in protein samples is caused by the ultrasonic cavitation that increases the surface, area of proteins. With results of electrophoresis one can conclude that ultrasound treatment induces protein composition changes in isolates and concentrates, and it depends on used frequency and intensity of ultrasound and also on time of treatment. pH didn't change significantly upon ultrasound treatments. Temperature increased for all treatments with highest increase was observed for 20 kHz/30 minutes treatment.