Effect of pH and Salts on the Solubility of Egg White Protein

The solubility of 1% dispersions of freeze‐dried (FD) and commercial spray‐dried (SD) (containing less than 0.1% SDS) egg white protein (EWP) was determined in water and in 0.1, 0.3, and 0.5M NaCl and NaI, and 0.01, 0.05, and 0.1M Na 4 P 2 O 7 at pH 3, 5, 7, and 9. Protein solubility generally increased at higher pH and salt concentrations over the ranges studied. Both I and P 2 0 7 ions, but not Cl, substantially increased the apparent solubility of FDEW, but had less effect upon the solubility of SDEW. Both NaI and Na 4 P 2 0 7 changed the character of the solvent in a way similar to that of SDS, a known protein denaturant and solubilising agent. The effect of these two salts upon EWP solubility was more pronounced than for bovine serum albumin.