Effects of ionic strength and denaturation time on polyethyleneglycol self-diffusion in whey protein solutions and gels visualized by nuclear magnetic resonance

Pulsed field gradient NMR spectroscopy was used to determine the poly(ethylene glycol) (PEG) self-diffusion coefficient (D-PEG) as a function of NaCl concentration (C-NaCl) and denaturation time (t(D)) in whey protein solutions and gels. D-PEG in the gel decreased with increasing C-NaCl concentrations and increased with increasing t(D); the increase ceased for all PEGs when the gel was fixed. This increase was more pronounced for the 82250 g/mol PEG than the 1080 g/mol PEG. Moreover, the diffusion coefficient of nonaggregated whey protein was measured and an increase for longer t(D) was also observed. Scanning electron microscopy images and H-1 spectra demonstrated that D-PEG were related to the structure changes and to the percentage of beta-lactoglobulin denaturation.