Ultrasound frequency effect on soybean protein: Acoustic field simulation, extraction rate and structure

This study endeavored to develop a method to evaluate the effect of ultrasound frequency on soybean protein extraction. In the ultrasonic frequencies range from 20 to 52 kHz, 28, 35, and 45 kHz were predicted to be the resonance frequencies in the ultrasound-assisted extraction (UAE) process of soybean protein by simulating the acoustic field distribution. The absolute sound pressure and the relative standard deviation could be wellcoordinated via frequency regulation. The extraction experiment of soybean protein showed that the extraction rate was improved significantly (p < 0.05) with the aid of ultrasound. The extraction effect was optimal at 28 kHz and the extraction rate was improved to 73.35 g/100 g from 46.09 g/100 g of control under the same condition. The structure of the extracted protein was analyzed by the spectrum to further explore the mechanism of the effect of ultrasonic frequency. Spectral analysis showed that 20, 28, and 35 kHz had a significant influence on the structure of protein molecules. Therefore, acoustic field simulation can be used as one effective method for selecting ultrasonic frequency, which could help to optimize equipment and improve efficiency.