Multiscale characterization of whey protein isolates under high NaCl environments

The objective of this study was to examine the influence of high concentration of NaCl on the secondary structure, hydrophobicity and opacity of Whey Protein Isolates (WPI) dispersions. Dispersions were studied at a constant protein concentration (5%) in high NaCl environments (from 0 to 6%). Protein dispersions were characterized as to their color and protein surface hydrophobicity. Additionally, changes in secondary structures upon salt increase were followed by Fourier Transform Infrared Spectroscopy (FTIR). The estimations of secondary structural elements from Amide III assignments were correlated to results obtained from Amide I. Upon salt increase, no differences in secondary structure were observed whereas the protein surface hydrophobicity related to the number of hydrophobic sites available decreased. Concurrently, color differences (Delta E) related to evolution of the protein dispersions containing variable NaCl concentration increased significantly.