Ultrasound-assisted pH shifting modification of Euryale ferox protein: physicochemical, structural and functional properties

Abstract

The impacts of integrating ultrasonic treatment (560 W) with pH shifting at pH 2, 3, 7, 11, and 12 on the physicochemical, structural, and functional attributes of Euryale ferox protein were investigated. The results indicated that the ultrasound-assisted pH 11 modified Euryale ferox protein exhibited an increase in the absolute zeta potential from 5.802 mV (pH 7 control) to 9.283 mV, solubility from 17.88% to 50.68%, surface hydrophobicity from 22.27 μg to 40.87 μg, foaming capacity from 52.78% to 70.55%, and emulsifying activity from 10.81 m2/g to 13.69 m2/g, along with the maximum UV absorption peak intensity. Meanwhile, the particle size, turbidity, and intrinsic fluorescence intensity of Euryale ferox protein under this condition were reduced. FT-IR profiling provided evidence that the combined treatment altered the secondary structure of Euryale ferox protein, as evidenced by increased β-sheet and random coil contents alongside decreased α-helix and β-turn fractions. Rheological results demonstrated that the combined treatment reduced both the shear stress and apparent viscosity of Euryale ferox protein. Therefore, ultrasound combined with pH shifting modification conferred considerable improvements upon the functional characteristics of Euryale ferox protein by inducing structural modifications, thereby enhancing its prospective applications in food processing.