Today whey is a valuable, reasonably priced raw material for the production of a wide variety of products. It is evaporated and dried without further selective separation to give whey powder.
Whey powder is relatively expensive to produce because the whey has a low dry matter content – approx. 6–6.5% - and lactose crystallisation is required.
Since amorphous lactose is sticky and very hygroscopic and would cause problems during drying, the lactose has to be crystallised following evaporation and prior to drying.
The qualities of whey powder are classified by the degree of lactose crystallisation. This may vary between 0 and 95% and gives caking tendencies of between 0 and 100%.
In order to crystallise lactose, the whey is concentrated to 42–60% dry matter by evaporation or reverse osmosis and evaporation. The concentrate is initially cooled to 30°C and the lactose crystallised out over 4–24 hours. Crystallisation is set in motion by inoculation with fine lactose crystals. During crystallisation the temperature is further reduced to 10°C. Lactose crystallises as alpha-lactose monohydrate. After crystallisation the concentrate is spray dried.
Whey concentrate and whey powder are used as ingredients in the food, pharmaceutical and cosmetic industries. Whey powder can replace skim milk powder in various products. Whey powder is used in baked goods because it improves the taste, especially of white bread and biscuits. It also gives better crust browning and keeps baked goods fresher for longer. Whey concentrates and whey powder are used to a certain extent in the beverage industry.
The opportunities for using whey are improving dramatically as a result of modern membrane separation technology. Modern processes can overcome the dominance of lactose (72 to 74%) and the high minerals content (8%) restricting the use of whey powder. See membrane separation methods.