Abstract: The effect of combined treatment with ultrasound and different NaCl concentrations (0, 15, 30, 45, and 60 mmol/L) on the fibrillation of whey protein isolate (WPI) was examined. Changes in the morphology, aggregation process, turbidity, emulsifying activity, and emulsion stability of different WPI fibrillar aggregates were investigated using transmission electron microscopy (TEM), fluorescence spectrophotometry, ultraviolet visible (UV-Vis) spectrophotometry, and laser scanning confocal microscopy (LSCM). The results showed that the combined treatment changed the morphology and polymerization kinetics of WPI fibrillar aggregates. Compared with WPI, ultrasound combined with 15 mmol/L NaCl increased the maximum rate of increase in fluorescence intensity, resulting in maximum fluorescence intensity of 985.213. Ultrasound combined with 60 mmol/L NaCl reduced the lag time to 0.784 h. The kinetic changes in fibrillar aggregation might be the reason for the morphological changes in fibrillar aggregates. The fibrillar aggregates formed by ultrasound combined with 30 mmol/L NaCl had the best morphology and the highest emulsifying activity index (1.44 m2/g) and emulsion stability index (73.21%). The fibril aggregates could evenly wrap around the surface of oil droplets.

Key words: whey protein isolate; aggregation kinetics; fibrillar aggregates