The R-O process is usually carried out at relatively high pressures. FDA has recognized these processes, when applied to whey, and they are currently being used in Grade A plants to process Grade A sweet and acid whey to produce dry and whey protein concentrate which are then utilized as ingredients, where permitted by the Standards of Identity, to add to Grade A milk products. Some of the resulting food, although it may look and taste like cheese, does not have the same physical and chemical properties as the cheese defined in Part 133 and may or may not be nutritionally equivalent. This may be as long as 10 to 12 hours in duration. The process generally takes place at temperatures of 75x-95xF. These temperatures are favorable to bacterial growth.
Most membranes are very delicate in nature.
They must be kept continually wet. The backing upon which they are cast is open and porous in nature, usually it is a woven plastic fiber. All of these factors make cleaning, sanitizing and maintaining a sanitary condition very difficult. Most plants, working with their equipment and detergent supplies have been able to obtain satisfactory conditions. Some people have suggested that UF or RO units be placed on dairy farms.