[7]. In addition, a lower transmembrane pressure (TMP) than that applied to RO can be used to obtain comparable fluxes. NF membranes wears ionogenic groups, and, consequently, their separation mechanisms involve both steric (sieving) and electrical (Donnan) effects. Partial loss of electrolytes is advantageous to several applications. A typical example is whey concentration: the use of NF yields partially demineralised INTRODUCTIONNanofiltration is a relatively new pressure-driven membrane process with growing applications to various fields such as food industry and water treatment. A peculiar feature of NF membranes is their low retention towards monovalent ions, whereas retention of higher ions and sugars is comparable to that obtained by reverse osmosis Original articleThe pre-concentration of milk by nanofiltration in the production of Quarg-type fresh cheeses Abstract -Milk pre-concentration by nanofiltration (NF) was proposed for fresh Quarg-type cheese manufacturing. NF process modelling by means of model solutions showed that transmembrane pressure and flow velocity had a clear effect on both permeation flux and lactose retention, that a rise in temperature resulted in an increase in permeate flux and a decrease in lactose retention, and that monovalent ion retention depended heavily on the concentration. Milk was concentrated 2 to 3 times by NF. Permeation fluxes were in a range of 10 to 41 kg·h -1 ·m -2 and solute retentions were in accordance with the results from model solutions. Quarg obtained using milk NF retentates was naturally sweeter (61.52 ± 4.30 g·L -1 lactose) than traditional fresh cheese and had a high calcium content (2.01 ± 0.33 g·L -1 ) and no bitter taste. Whey had a higher total solids and lactose content and, therefore, required an easier treatment than normal Quarg acid whey.