Physicochemical analysis of casein solubility in water-ethanol solutions

Abstract

Due to the change in the apparent acid dissociation constant, when ethanol was added to water solutions of an industrially produced spray-dried sodium caseinate, the solution's pH increased proportionally to the reciprocal relative dielectric constant (1/). The pH increased by 1 unit when the ethanol volume fraction reached about 0.60. The casein solubility profile at 20 C as a function of pH (3-8) and the ethanol volume fraction (0-0.75) was quite well represented by the equation describing the ionisation process. The pH inflection point and the slope coefficient were approximately linearly related to 1/. The evolution of the electrostatic surface potential ( 0 ) and the zeta potential () explained the changes in casein solubility as a function of pH and the dielectric constant of the solvent. The increase in 0 by 37 5.2 mV or in by 8.6 1.4 mV raised casein solubility from 10 to 90%. casein / solubility / ethanol / dielectric constant / electrostatic potential