The aim of this contribution is to show some important physical-chemical parameters that must be taken into account during the crystallization of proteins. For this purpose, we have calculated the overall free energy, the chemical potential, the entropy, and the enthalpy for a model protein. Dynamic light scattering techniques were used in order to study how far the system was from the equilibrium after obtaining single crystals. Additionally, we show the solubility plot of the model protein in order to explain the plausible crystal growing zone. We have also presented the first experimental approach to infer the equilibrium state by using light scattering techniques. Classical thermodynamic measurements were obtained and compared with our approach. It has also been possible to explain the role of ionic strength and temperature in the crystallization of thaumatin. Finally, we have demonstrated how our crystal quality predictions obtained from dynamic light scattering and X-ray diffraction analyses can be compared with classical predictions.