Solubility of systems containing egg yolk proteins and xanthan gum (0.083, 0.042, 0.021 and 0.011% w/v) had been studied in different temperatures (10, 25 and 35 °C), pH (3.0, 4.0, 6.5, 8.5 and 10.0) and concentration of NaCl (0.2, 0.4 and 0.8) mol/L. According to the data, a lesser solubility of the proteins can be observed in the pH system that is more acid. An increase in the solubility of the proteins of the egg yolk can also be observed in high concentrations of xanthan gum associated with the increase of NaCl concentration. The nonlinear model used to adjust gave a good fit adjusted to the solubility data in the studied conditions. The thermodynamic parameters were calculated indicating that the entropic effects in the solubility process are more important than the enthalpic effect. The negative values found for free energy indicate the spontaneity of the process of the solubility of the proteins and their viability. © 2010 Springer-Verlag.