Small angle neutron scattering and viscoelasticity study of the colloidal structure of aqueous solutions and gels of a globular protein

Small-angle neutron scattering and viscoelasticity measurements were performed on β-lactoglobulin solutions and heat-set gels at pH 9 and low ionic strength. The rheological properties of the solutions were characterized by antithixotropy and viscoelasticity.In the case of aggregates and gels, a peak in the scattering curves was observed; qmax varied as C0.5. This correlation peak vanished with increasing ionic strength. The dilution of the aggregates showed that the correlations were lost and that the aggregates displayed the same internal structure as the gels. Gels formed at low ionic strength indicated a liquid type viscoelastic behaviour. At high ionic strength, fractal structures of the aggregates would be observed between 400 and 40 Å with df= 1.3 at low protein concentration and 1.75 at a higher concentration. Subsequent dilution did not change the fractal dimension of these structures