Membrane separation has become a popular technique used in the food industry. Some of its application includes purification of water, concentration and clarification of fruit juices, milk products and many other beverages. In membrane separation, a fluid containing a mixture of solutes is passed through a membrane. Separation of solutes happens depending on how readily the solute permeates the membrane. The pore size and structure of the membrane affects the separation of the fluid. 

 

The general principle of most membrane separation methods requires the use of an external pressure to create a pressure gradient as the driving force. The mass transport is dominated by the convective flux through the pores. Since ultrafiltration membranes are usually asymmetrical and the pores facing the feed side are usually larger in size, thus molecules which are smaller than the pores will be able to permeate across the membrane whilst the larger molecules remain in the retentate.