Ultrafiltration (UF) is the main membrane process used for cheese milk concentration; it leads to an increase in protein content while keeping the composition of the serum phase constant. Reverse osmosis (RO) and nanofiltration (NF) techniques could be used for milk concentration before cheesemaking but their selectivity toward milk salts is likely to lead to different characteristics in terms of soluble: colloidal equilibria and impair the cheesemaking properties of concentrates. The objective of this work was to compare the composition of milks concentrated using UF, RO and NF. Batch lots of pasteurized skim milk (SM) were concentrated by means of a pilot-scale filtration system (GEA NIRO) operated at 50°C until a volume concentration factor of 3× using 3 different spiral-wound membranes (Synder Filtration): UF (10kDa), RO (99.4% rejection of NaCl), and NF (99 and 40% rejection of MgSO₄ and NaCl respectively). The skim milks and their corresponding concentrates were characterized for protein and salts soluble: colloidal distributions and viscosity. Phase separation was done by ultracentrifugation at 10000g for 1 h; and milks and their respective supernatants were analyzed for protein and main salts (K, Ca, Mg, Na, P). Totals solids and apparent viscosity were significantly higher for NF and RO milks (P > 0.05) compared with UF. Both divalent and monovalent ions were significantly higher in the serum phase of RO milk while only divalent ions were concentrated in NF (P > 0.05). Despite the increased ionic strength for RO and NF, ionic activities of the salts were still higher in RO and NF milks than in UF milk and SM (P > 0.05). Milk concentrates composition and milk salts soluble: colloidal distribution are significantly affected by membrane selectivity. These differences may lead to impaired cheesemaking properties of RO and NF concentrates.