Samira Feyzi - Department of Food Science and Technology, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.

This study aimed to probe the structural changes of whey protein isolate (WPI) as a function of pH (4-9) and NaCl concentrations (0-0.5M) using fluorescence, 3D-fluorescence and circular dichroism (CD) spectroscopies. Findings of UV-Vis spectroscopy and atomic force microscopy (AFM) confirmed the aggregation of WPI at pH 4, indicating associations in whey proteins. WPI had looser secondary and tertiary structures at acidic (pH 4 and 5) and basic (pH 9) conditions compared with pH 7.2 and 6; as well as at 0.1 and 0.3 M NaCl compared with other NaCl concentrations.

Aggregation, Circular dichroism, Fluorescence spectroscopy, Ionic strength, pH, Secondary structures, Tertiary structures