This study proposes a fractionation of proteins using solutions (5%) of Whey Protein Isolate (WPI) and supercritical carbon dioxide (scCO2) in a continuous reactor. The experiments were performed at different values of pressure, temperature, and residence times - 65.4, 34.3, and 32.3 min, respectively. a-lactalbumin (a-LA) and ß-lactoglobulin (ß-LG) levels were determined by HPLC. WPI used without treatment showed an a/ß ratio = 0.40. 16 MPa/55 °C and 16 MPa/60 °C were the conditions that suffered the most positive and negative influence of the increase and decrease in residence time, respectively. In the most severe condition, 24 MPa, 65 °C, and 4.0 mL·min-1, circular dichroism indicated that, despite not having obtained a high level of pureness, the fractionation technique employing scCO2 did not denature the proteins a-LA and ß-LG.