Effect of pH on turbidity, size, viscosity and the shape of sodium caseinate aggregates with light scattering and rheometry.

Abstract

The characterization of sodium caseinate solutions as a function of pH was determined using titration with HCL through turbidimetry in different concentrations (0.03wt.%, 0.045wt.%, 0.06wt.%, 0.09wt.%, 0.2wt.%, and 0.3wt.%). Additionally, the coupling of slow in situ acidification of the solution and rheometry was utilized to gain deeper insights into pH-induced structural transitions during the self assembly process and particle size distribution analysis have been used to determine the behavior of sodium caseinate solutions in different pHs. The formation of aggregates during the acidification process was clearly visualized using microscopy. Surprisingly the viscosity of sodium caseinate solution at pH 4.64 was maximum and decreased by lowering pH. Particle size analysis confirmed the onset of big aggregates on decreasing pH but further acidification led to formation of smaller aggregates. A small concentration effect on pI was seen where at sodium caseinate levels of 0.03wt.% the pI occurred at 4.29, where at sodium caseinate levels of 0.30wt.% pI value was 4.64.