Separating profits

Membrane processing has been used in the dairy industry for years - to concentrate whey, reduce evaporator or drier loads, and remove water, lactose and minerals from whey to make whey protein concentrate (WPC). Now, current advances in membrane technology are modifying standard uses and creating new opportunities for dairy processors.

Ultraosmosis is permeable to water, monovalent ions, and other small molecules but retains proteins and sugars. It is applied to demineralize, fractionate (in combination with other membrane types), or clean process streams. It can often partially or completely replace ion exchange and electrodialysis processes.In searching for a way to clarify the low-solids juices, Clermont considered all the alternatives. It pilot-tested diatomaceous earth, ceramic filtering, zirconia membrane and reverse osmosis before selecting an ultrafiltration system engineered and manufactured by APV Crepaco, Lake Mills, Wis.Ultrafiltration was the second of the membrane separation processes to be developed. Ultrafiltration membranes, which retain proteins and fats, and are used to manufacture whey protein concentrates (WPCs), gelatins, meat protein concentrates, delactosed whey, clarified wines and juices, and a wide selection of cheese.Inorganic membranesThe European process uses microfiltration (MF) to remove fat from the whey before it is concentrated by UF. The MF system uses membranes with pore sizes that allow the protein to pass through but retain the fat. One problem with the process is that the fat molecules plug up the membrane's pores. Only careful control of flow rates and cross-membrane pressures minimize clogging.The futureMembrane filtration's originsAnother developmental frontier is being opened up by Dr. Kris Berglund, associate professor of chemical and agricultural engineering at Michigan State University (East Lansing, Mich.). Berglund is studying the potential application of glassy coatings to inorganic membranes as a means of increasing their selectivity. The technology's potential extends beyond food processing applications to include the development of highly-selective in-line chemical or food ingredient sensors.

In addition to eliminating traditional plate and frame diatomaceous earth filters, membrane clarification typically provides 96 to 98 percent juice recovery compared with 85 to 95 percent for other filtering methods. Membrane concentration, done by RO, can increase juice concentration from its original level of 11 to 12 brix to as high as 60 or 70 brix, although this produces a thick and viscous product. To overcome this problem, systems that remove half the water with membranes and then finish the concentration with an evaporator can be installed. This partial concentration by membranes enables processors that already have an evaporator to double its output for a relatively small expenditure.

Author: Jack Mans