Ever since the early 1980s, when membrane filtration first began gaining a foothold in the dairy industry, the staff at DSS has been working on the development, sales and design of membrane filtration systems for dairies all over the world.
Membrane filtration is now used in an increasing number of fields, and this technology will play a crucial role in the production of new, innovative dairy products and dairy-based food ingredients in the future.
Technology - Filtration at molecular level
A liquid consists of a number of components with different molecular or particle sizes. By using membranes with pores of different sizes, it is possible to separate exactly the components you wish to concentrate or remove from the liquid stream.
Membrane filtration is a straightforward technology that separates a liquid into two streams using a semi-permeable membrane.
A difference in pressure forces the components that are smaller than the membrane pores through the membrane as "permeate". The remaining components are retained as "retentate". A substantial flow moving parallel to the membrane prevents the membrane surface from getting blocked during the process. This is known as cross-flow filtration.
Depending on the density of the membrane, the process is called reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) or microfiltration (MF).
Benefiting From Whey
The most common application of membrane filtration in the dairy industry is the treatment of whey from cheese manufacture.
If the whey is to be transported for further processing or to be used as animal feed, it is typically concentrated 1.5 to 3 times in an RO plant. The permeate is used as process or CIP water.
If the whey is concentrated using NF, the retentate is simultaneously demineralised. In certain cases, NF can be used as a cost-effective alternative to RO.
Whey that has been concentrated using RO or NF can be processed directly into whey powder.
UF allows the concentration of whey proteins along with the simultaneous separation of minerals and lactose. A standard UF plant typically produces whey protein concentrate (WPC) with a protein content of 34 to 85%.
By using supplementary techniques, such as chromatography and microfiltration, it is possible to isolate the proteins even further to produce whey protein isolates (WPI).
Tailor Made Milk
RO can be used to pre-concentrate the milk before it undergoes evaporation to make milk powder or simply to save on transport costs.
If UF is used to concentrate the milk, the result is a retentate with high protein content, whereas minerals and lactose are removed. The retentate is used for purposes that include the manufacture of different types of cheese and milk protein concentrate (MPC), or it can be refined still further to produce milk protein isolate (MPI).
The protein content of milk varies, but can easily be standardised using UF. Protein standardisation is used extensively in the manufacture of yoghurt, milk powder, cheese and other products.
Microfiltration is a relatively new technology in the dairy industry. It provides opportunities for regulating the casein content of the milk or for removing microorganisms.
High Cheese Yield and Quality with UF
Feta and similar cheese types are manufactured by full concentration of the milk using UF. Culture or acid, rennet, salt and other additives are added to the retentate, and it can then be cast straight into the appropriate packaging.
Fresh cheese types based on fermented milk or cream, such as quark or cream cheese, can also be manufactured using UF. After fermentation, the product is concentrated to the desired level followed by final treatment and packaging. The UF process results in a high, uniform quality and a very high yield. At the same time it is possible to manufacture several different products on the same UF plant.
High-quality cheese with clean brine Microfiltration removes impurities and harmful microorganisms from the cheese brine swiftly and efficiently, while preserving the natural chemical balance of the brine. DSS has developed the special BrineClear™ concept, which has proved to be a supremely good solution, technically as well as financially.
Every Drop Counts
UF permeate from whey or milk mainly contains minerals and lactose. This can be concentrated with RO up to 23% dry matter and be used for animal feed or be processed still further to lactose powder. If a purer lactose fraction is required, the permeate can be concentrated with NF, which will remove some of the minerals.
Streams of process water, such as RO permeate, evaporation condensate and flush water, are cleaned in an RO polisher to such an extent that the water can be reused.
Membranes and Expert Services Go Hand In Hand
The heart in any membrane filtration process is the membrane itself, and choosing the best membrane for a given process is often a difficult task. Membrane type, plant design and processing parameters should be carefully matched to meet the desired performance and cost-efficiency of the overall process.
DSS is one of the worlds´ largest providers of membranes for dairy applications, and we can supply membranes from a range of recognized membrane manufacturers.
We supply replacement membranes for all plant types - irrespective of the previously installed membrane type or the original plant manufacturer. Together with this, we are able to offer the service of a membrane expert to install the membranes and fine-tune the operation of the plant for maximum performance.