Membrane filtration is often used to supplement conventional centrifugal separation processes based on gravity differences.     Alfa Laval nanofiltration spiral membranes use membranes with pores that are very small - down to 300 daltons. Operating at pressures of up to 50 bar, small ions pass through, whereas larger ions and most organic components do not. Alfa Laval nanofiltration spiral membranes are used for the high-yield concentration and demineralization of products such as whey and ultrafiltration permeate. These special membranes are used for filtering out large salts with a divalence in excess of 2, while small monovalent salts pass into the permeate. They can also be used in producing low-alcohol beverages, because the alcohol component passes through the membrane, while the colour and aroma remain in the retentate.