The primary role of a membrane is to act as a selective barrier. It should permit passage of certain components and retain certain other components of a mixture. Membrane is a phase that acts as a barrier to prevent mass movement but allowing restricted and/or regulated passage of one or more species through it (Lakshminarayanaiah, 1984). In the dairy industry, membrane processes used are microfiltration, ultrafiltration, nanofiltration and reverse osmosis. The use of reverse osmosis and ultrafiltration was first started in 1960 for desalination and water treatment. The process gained entrance in food industry, particularly the dairy, in the seventies and its application increased dramatically in the 1980s. The first pilot studies on microfiltraion of whole milk were reported in 1987 while the nanofiltration has been in use in dairy industry only very recently. What distinguishes the membrane processes is the application of hydraulic pressure to speed up the transport processes. The nature of the membrane controls which component permeated and which component is retained. Reverse osmosis is a dewatering technique while ultrafiltration is a method for purifying, concentrating and fractionating macromolecules or fine colloidal suspensions. Microfiltration is a loose ultrafiltration and allows separation of suspended particles, i.e. fat globules, microorganisms’ etc. from dissolved substances in a feed stream. The principle application of nanofiltration is in partial demineralization of whey. The membranes are made up of different types of materials-naturally available materials such as cellulose, or synthetic polymers such as polycarbonate, polyethylene, polysulfone, or modifications of existing polymers, such as sulfonated polysulfones or entirely new polymers developed specifically for membrane application. Most membranes are manufactured in the “flat sheet” form and in some cases they may be cast directly on to the module itself e.g. in tubular modules or may be extruded or spun into hollow fibers directly. In India, the use of membranes presents several limitations such as high initial capital cost of the equipment installation, lack of indigenous backup support for replenishment of membranes, inadequate technological expertise of the plant operators, fouling of the membranes, etc.