Abstract:

The objective of the present study was to investigate the effects of different pH values, temperatures, NaCl concentrations on hydrophobicity of whey protein isolate (WPI) exposed to hydroxyl radical-generating systems (HRGS) with different concentrations of H2O2 (1 — 20 mmol/L) or FeCl3 (0.1 — 2 mmol/L) for 1, 3 and 5 h. The results showed that the hydrophobicity of WPI was significantly influenced by oxidation and various environmental conditions. The maximal hydrophobicity of WPI was 9559.2 when exposed to 5 mmol/L H2O2-0.1 mmol/L FeCl3-0.1 mmol/L ascorbic acid system, which was 4.88 times that of the control and obviously higher than that of WPI exposed to HRGS systems with different concentrations of FeCl3. The hydrophobicity was high at pH values far away from pI 7.0 and was enhanced by the optimal temperature and NaCl concentration. These results suggest that the hydrophobicity of WPI is significantly affected by H2O2 concentration as well as environmental conditions during the oxidation process.

Key words: hydroxyl radical, oxidation, whey protein isolate (WPI), hydrophobicity