Effects of pH Values on Physicochemical Properties and Antioxidant Potential of Whey Protein Isolate-safflower Yellow Complexes

Abstract

Influence of pH values on physicochemical characteristics and antioxidant activities of whey protein isolate (WPI)-safflower yellow (SY) complexes were investigated at 25°C under the aerobic condition for 0, 3 and 6 d. Compared with WPI, WPI-SY had a less particle size at pH 3.5, 6.5, 7.5 and 8.5 from 0 to 6 days. Fluorescence intensity of WPI-SY complexes was appreciably less than WPI, which indicated that the partial tyrosine or tryptophan residues of whey protein had undergone certain changes. Compared with WPI and SY, thermal stability and emulsifying activity of WPI-SY complexes remarkably increased at different pH values. Meanwhile, antioxidant activities of WPI-SY complexes were higher than that of WPI or SY at pH ranged 4.5 to 9.5, kept for 3 and 6 d. Therefore, the interaction of WPI and SY at different pH values, could improve emulsifying activity of WPI and enhance antioxidant activity of SY.