Supercritical fluid extraction has been demonstrated as a reliable technique to extract triglycerides and volatiles from food. The aim of this work was to study the effect of temperature and pressure of supercritical fluid extraction using CO₂ on the physicochemical properties of buttermilk powder (BP) and whey protein isolate (WPI). The properties studied included triglyceride reduction, solubility, lactose crystallization, heat stability, particle size, particle morphology, foaming, and water activity. Triplicate treatments were applied to Land O’Lakes BP and Hilmar WPI using our supercritical fluid extractor (Waters Inc., Milford, MA). All results were statistically analyzed by ANOVA. Temperature ranges tested were 65 to 80°C, and pressure ranges from 250 to 350 Bar. Our resulting surface-response graphs indicate a much larger triglyceride extraction at 80°C and 350 bar. However, there is not a clear preference on these parameters when measuring solubility indices in either BP of WPI. The increase of solubility of treated BP was significantly higher than that of WPI as compared with untreated samples. This correlated with the lower concentration of triglycerides in WPI initial sample. Foam volume and stability was significantly reduced in BP but not in WPI. One particularly noticeable change was the particle size reduction of both treated powders when reconstituted and analyzed by static laser diffraction. However, this difference was only significant when compared with untreated samples. Other parameters measured were not significantly modified by the treatments tested.