• RO -used for dehydration of whey, UF permeate and condensate.
• NF -used when partial desalination of whey, UF permeate or retentate is required.
• UF -typically used for concentration of milk proteins in milk and whey and for protein standardization of milk intended for cheese, yoghurt and some other products.
• MF -basically used for reduction of bacteria in skimmilk, whey and brine, but also for defatting whey intended for whey protein concentrate (WPC) and for protein fractionation.

The general flow patterns of the various membrane separation systems are illustrated in figure 6.4.3.

Fig. 6.4.3. Principles of membrane filtration.