Acid-induced gelation behavior of soybean protein isolate with high intensity ultrasonic pre-treatments

High intensity ultrasonic (HUS, 20 k Hz, 400 W) pre-treatments of soybean protein isolate (SPI) improved the water holding capacity (WHC), gel strength and gel firmness (final elastic moduli) of glucono-δ-lactone induced SPI gels (GISG). Sonication time (0, 5, 20, and 40 min) had a significant effect on the above three properties. 20 min HUS-GISG had the highest WHC (95.53 ± 0.25%), gel strength (60.90 ± 2.87 g) and gel firmness (96340 Pa), compared with other samples. Moreover, SH groups and non-covalent interactions of GISG also changed after HUS pre-treatments. The HUS GISG had denser and more uniform microstructures than the untreated GISG. Rheological investments showed that the cooling step (reduce the temperature from 95 to 25 °C at a speed of 2 °C/min) was more important for the HUS GISG network formation while the heat preservation step (keep temperature at 95 for 20 min) was more important for the untreated GISG. HUS reduced the particle size of SPI and Pearson correlation test showed that the particle size of SPI dispersions was negatively correlated with WHC, gel strength and gel firmness.

Graphical abstractThe high intensity (105–110 W cm−2 or 0.33–0.35 W cm−3) ultrasonic (HUS) treated soy protein isolates were used to form GDL-induced gels. Water holding capacity, gel strength and gel firmness of the gels increased after HUS. Rheological properties, microstructure, free sulfydryl content and chemical interactions were changed.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Soy protein isolate (SPI) was treated by high intensity ultrasound (105–110 W cm−2 or 0.33–0.35 W cm−3). ► High intensity ultrasound (HUS) treated SPI was used to form GDL-induced SPI gels (GISG). ► Water holding capacity, gel strength and firmness of GISG increased after HUS. ► Microstructure, rheological properties, free sulfydryl content and chemical interactions were changed.