We wanted to explore if the concentration of minerals in milk protein products affected the functional properties such as in acid milk gels. Microfiltration (MF) was used to deplete whey proteins and minerals from acidified milk to create soluble casein isolate (SCI), which was compositionally similar to sodium caseinate. Yogurt gels were made from SCI, sodium caseinate, nonfat dry milk, and 4 commercial milk protein concentrates (MPC) that had some level of mineral reduction. All powders were rehydrated and standardized to 5% protein. Yogurt gels were made by inoculating milk with yogurt culture containing Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus, and fermented at 40°C until pH 4.6 for the MPC, and to pH 4.3 for sodium caseinate and SCI (both of which were supplemented with peptone to aid fermentation). Rheological properties such as gel stiffness and loss tangent were measured during fermentation, and yield stress was measured upon reaching the target pH. Buffering capacity was measured using acid-base titrations to indicate levels of insoluble calcium phosphate. Soluble calcium levels in rehydrated samples were determined in ultrafiltered permeate by performing inductively coupled plasma spectrometry (ICP) on the permeate. Calcium depleted MPC had a lower buffering capacity than nonfat dry milk, sodium caseinate and SCI had similar (very low) buffering capacities. Calcium depleted MPC also had lower soluble calcium levels than nonfat dry milk, whereas sodium caseinate and SCI had similar but very low levels of soluble calcium. Gels made from MPC had similar gel stiffness to nonfat dry milk, but had higher yield stress, indicating a more cross-linked yogurt gel. Sodium caseinate and SCI had similar (weak) gel stiffness during fermentation, but sodium caseinate gels exhibited higher yield stress values than SCI. Overall, this MF process produced SCI with similar acid gelation characteristics to sodium caseinate.