The effect of ultrasound on the physicochemical and emulsifying properties of soy proteins

In this study, the effect of ultrasound application on the physicochemical and emulsifying properties of soy protein emulsions was investigated. Ultrasound was treated to a soy protein isolate (SPI) solution at 5, 10 and 15 amplitude. Results showed that the ultrasound treatment reduced the droplets size of emulsions and caused an increase in the emulsifying activity and stability of emulsions at 15 amp. The effect of pre-heating and pH treatment on the ultrasound treated SPI emulsion was also analyzed. Increased heat treatment from 60 to 70 and 80°C showed better emulsification properties. The best functional properties were observed at pH 9 in comparison to pH 5 and pH 7. On the other hand, CaSO4-induced SPI gel-like emulsions were prepared by the cold-set and heat-set method. Ultrasound pre-treatment of SPI emulsions caused an increase in functional properties ofCaSO4-induced SPI gel-like emulsions. Gel-like emulsions were heated at 95°C for 20 min. Heat treatment, due to the structural changes in SPI molecules, led to smaller droplet size and uniform microstructure. And also, water holding capacity (WHC) and fat holding capacity (FHC) of gel-like emulsions increased.