Membrane separation processes are based on the principle of concentration-fractionation treatment of solutions without phase change. Ultrafiltration (UF) and reverse osmosis (RO) are well established pressure-driven membrane processes that are widely used in the dairy and other food industries throughout the world. Recent developments in the membrane technology have expanded the range of applicability of these traditional processes offering the processing industry new alternatives to the more traditional technological approaches. One such new development is nanofiltration (NF). Nanofiltration (NF) membrane processing was investigated as a method of deacidifying and demineralizing acid cheese whey as a function of temperature, pressure and pH. This study was focused on improving the demineralization rate achieved by commercial nanofiltration membranes by using laboratory-manufactured membranes. Model solutions of whey were applied as well as model solutions for each salt (single-salt solutions), allowing us in this way to study the performance and transport of salts when each salt is treated alone and when all are together (whey salts) in the feed solution.