A Variety of Different Characteristics
As a result of their composition and content (proteins, lactose and minerals), whey products can be difficult to dry. Whey fractions present a variety of different characteristics and, as such, need to be dried and processed according to their varying properties and characteristics. GEA is a market leader in whey drying technologies and offers solutions for whey products and derivatives including demineralized whey powder, lactose, permeate, whey protein concentrates (WPCs), whey protein isolates (WPIs) and sour/sweet whey.
GEA’s product range includes a number of different types of spray dryers, each of which has been designed for specific product compositions and powder properties.
Spray Drying without Crystallization
This process requires the following unit operations/processes: pre-heating, concentration, spray drying and pneumatic cooling in a vibrating fluid bed. Ordinary whey powder obtained using this process is fine, dusty, hygroscopic and susceptible to caking (often influenced by the type of whey and local climatic conditions). The stickiness, caking and associated problems of normal whey powder mainly result from the presence of unstructured crystalline lactose.
When spray drying milk products, lactose particles become amorphous and unstable in atmospheric air at normal humidities. Only alpha-lactose monohydrate is humid-stable. As the lactose content of whey powder comprises more than 70% of the total solids (compared with 30% in whole milk), it makes the spray drying process more challenging. However, it is possible to manipulate the drying process and convert the majority of the lactose to the stable alpha-lactose monohydrate form.
Spray Drying with Crystallization
To facilitate final crystallization, a pre-crystallization step can be included in the whey production process before spray drying. The viscosity of the concentrate is reasonably low, temperatures can be adjusted and controlled, displacement of used solution from the surface of crystals may be accelerated by agitation, and the required amount of suitable lactose crystals can be optimized by proper seeding.
Furthermore, there is normally sufficient time for the pre-crystallization process to reach the optimal (theoretical) degree of crystallization. The subsequent product is non-caking and, being agglomerated, is dustless and free flowing. The agglomerates tend to be small and, as such, the bulk density is relatively high.