Consecutive pH-shift and ultrasound treatment modify the physicochemical properties of whey protein isolate

The effect of pH-shifting treatment combined with ultrasound on physicochemical and functional properties of whey protein isolate (WPI) was investigated. After pH 2- or pH 11-shifting (1, 2 and 3 h) and ultrasound treatment (600 W, 30 min), particle size distribution of WPI became narrower and its fluorescence intensity decreased significantly. After WPI was treated with pH 11-shifting for 3 h and ultrasound, it showed the maximum surface hydrophobicity and lowest turbidity (P < 0.05). Meanwhile, pH 2-shifting treatment (3 h) combined with ultrasound could improve emulsion stability of WPI. However, consecutive pH 11-shifting (1-3 h) and ultrasound significantly reduced the emulsifying properties of WPI. Therefore, the combination of pH 2-shifting and ultrasound was a significant method to improve the physicochemical properties of whey proteins. (C) 2021 Published by Elsevier Ltd.