Milk is the principal source of lactose (milk sugar), which represents a very large energy potential. Lactose has a number of unique properties which can be used in a variety of products.
Some of the food products in which lactose is used are listed below:
- Baked products
- Canned fruit
- Dairy products
- Dry soups, sauces
- Infant formulas
- Instant drinks
- Jams, marmalades
- Mayonnaise, salad dressings
SPX FLOW's in-depth knowledge and active involvement in the development of the world's whey processing industry, combined with proven experience in project management of major capital projects, makes SPX FLOW the ideal partner for the design and installation of state-of-the-art lactose processing equipment.
SPX has experience in the production of lactose from both whey and de-proteinised way. The basic processing steps in the manufacture of lactose are shown below:
Lactose from whey
The first step in preparing the whey for lactose production is to separate the cheese fines and to remove the fat as whey cream. Then the whey is evaporated to a TS content of 50-65%. The most important considerations are that the lactose content should be as high as possible and that the evarporation temperature is sufficiently low to avoid protein denaturation. The next step after evaporationis crystallisation (see below).
Lactose from deproteinised whey
After the whey has been clarified, the proteins must be removed. This can can be accomplished in two different ways: (1) denaturation of the proteins, and (2) ultrafiltration. Denaturation can take place by heating the whey to 90-95¸C for 15 minutes or more at a pH of 4.5, followed by a pH adjustment to 6.2. However, ultrafiltration is now a more popular method. After denaturation, the whey is evaporated to 60-65% TS.
When ultrafiltration is used to deproteinise the whey, the premeate is suitable for lactose production. If required, the permeate can be pre-concentrated in a nanofiltration plant during which a number of salts are also removed. The permeate is evaporated to a TS content of 60-70%. Even if the main part of the permeate is lactose, it still contains a certain amount of calcium phosphate. It may therefore be necessary to pre-treat the permeate in order to prevent excessive scaling of the evaporator.
Alternatively, the evaporation process may take place at a lower temperature and pH.
The evaporated concentrate is fed to crystallisation tanks, and after seeding and slow cooling, the lactose will become sufficiently supersaturated to crystallise. For crystallisation, the lactose solution must contain either a crystal seed or an impurity such as precipitated calcium phosphate.
The cooling rate should be slow enough to allow the formation of large crystals. The crystals should be tomahawk-shaped and their size should range from 200 to 600my.
Decantation and drying
When the crystallisation process is complete, the crystals are separated from the rest of the concentrate, the so-called mother liquor, in a decanter. The crystals are then washed, separated from the wash water in a special lactose centifruge. The crystals are dried in a stationary lactose fluid bed dryer. The drying temperature in the first section is 110-120°C. Depending on the intended application, the lactose is dried to a content of less than 0.5% free moisture. Finally, the crystals are ground to the required size, typically between 50 and 150my.
The processing parameters most important for the yield include:
- a high lactose content in the concentrate
- slow cooling during crystallisation
- low temperatures at the end of the crystallisation process
- large crystals
- low volume of wash water
A realistic target is a yield of approximately 65% of the total available lactose.
Utilization of mother liquor
Mother liquor from whey can be evaporated to a TS content of almost 50% and subsequently dried.
Process Diagram and Benefits
- SPX FLOW's global experience as a supplier of APV processing technology and equipment for whey products is a key factor in our ability to deliver cost-effective solutions tailored to individual customer requirements.
- Weoffer an enormous range of resources to the dairy industry in process engineering, equipment manufacturing, project management - for both large and small projects - and world-class development facilities.
- SPX FLOW turns losses into profits: efficient production of lactose from the by-products of whey processing, provides a viable and valuable end product.