Pulsed electric field-induced structural modification of whey protein

Abstract

The objective of this study was to evaluate the effect of pulsed electric fields (PEF) on structural modification and surface hydrophobicity in whey protein isolate (WPI) of different concentrations (3% and 5%) by using fluorescence spectroscopy technique. The increases in intrinsic fluorescence intensity and surface hydrophobicity were positively correlated with functional properties. The effects of PEF treatments (electric field intensities of 12, 16 and 20 kV cm-1 and pulses ranging from 10-30) on intrinsic fluorescence intensity and surface hydrophobicity of WPI for aromatic 1-anilino-naphthalene-8-sulfonate (ANS) probe were evaluated. PEF treatments of WPI resulted in an increase in intrinsic tryptophan fluorescence intensity with a 2-4 nm red shift at electric field intensity of 20 kV cm-1 and 30 pulses, which indicated changes in the polarity of tryptophan residues microenvironment of the whey proteins, changing from a less polar to a more polar environment. The ANS fluorescence intensity of WPI also increased with a 2-4 nm blue shift at electric field intensity of 20 kV cm-1 and 30 pulses, indicating that WPI fractions were partially denatured under this PEF treatment condition. Also, the exposure of more hydrophobic regions resulted in an increase in the ANS fluorescence intensity. These results indicated that PEF treatment of WPI yielded increases in surface hydrophobicity.