Structure and emulsifying properties of whey protein isolate: Effect of safflower yellow concentration

The effects of different concentrations of safflower yellow (SY) on the structure and emulsifying properties of whey protein isolate (WPI)-SY complexes were investigated at 25 degrees C for 0, 3 and 6 days. About 92.6%, 93.75%, and 95.47% of the free sulfhydryl groups from the WPI-SY complexes were lost over 0, 3 and 6 days, respectively, in the presence of 2% SY. Meanwhile, the fluorescence intensity of the WPI-SY complexes also weakened obviously, indicating that the tryptophan residues micro-environment underwent certain changes. Furthermore, fourier transform infrared spectroscopy demonstrated that SY increased the proportion of WPI beta-sheets and decreased the proportion of beta-turn structures. The particle size of the WPI-SY complexes increased as the SY concentration was increased from 1 to 4%. Compared with SY or WPI, the antioxidant activity of the WPI-SY complexes was enhanced with SY ranged from 0.25 to 4%. SY triggered emulsifying activity of WPI initially increased and then decreased. Therefore, SY could enhance the emulsifying properties and antioxidant activities of WPI-SY.