Whey has been known for decades as a product of high nutritional value. Today, the development of markets using whey powder and fractions of whey as ingredients in foodstuffs for human and animal consumption have transformed the previously troublesome by-product whey into a valuable product for the dairy and cheese-making industries.

There are two main groups of whey:

Sweet whey. This is also termed cheese whey and is produced during cheese-making, when rennet is used. Sweet whey forms a very large family of products. Their compositions may vary only slightly but their properties are very different. The pH value of sweet whey can range between 5.2 and 6.7
Sour whey. This can be acid whey, quark or cottage-cheese whey and sour sweet whey. Acid whey, also known as casein whey, originates from the manufacture of casein by means of lactic acid and hydrochloric acid. The origin of quark or cottage-cheese whey is self-explanatory. Lactic acid created through natural fermentation gives the whey a high acidity. The pH values of these types of whey range from 3.8 to 4.6. If insufficient care is given to the cheese whey, it becomes more sour by continued natural fermentation. Such a process is of course undesirable so that soured (not sour) whey cannot be considered a natural product

All types of whey can be spray-dried. Each, however, requires its own handling techniques. Layouts for spray-dried whey can vary from the very simple to the sophisticated. Generally speaking, sweet (cheese) whey is easier to dry than acid whey. The main operations used for the manufacture of whey powder are as follows:

Preheating
Concentration
Flash cooling
Precrystallization
Spray drying
Cooling in a vibrated fluid bed
Spray Drying without Crystallization Treatment
Processing consists of preheating, concentration, spray drying and pneumatic cooling.

Ordinary whey powder obtained by this process is very fine, dusty, hygroscopic and therefore caking. Hygroscopicity and caking are influenced by the type of whey and by local climatic conditions. The hygroscopicity, caking and all the problems associated with the stickiness of ordinary whey powder are mainly due to lactose being present in an amorphous glassy state.

In the spray drying of milk products, lactose is in an amorphous state and is not stable in atmospheric air or normal humidity. The only form of lactose that is stable to humidity is a-lactose monohydrate. Since the lactose content of whey powder comprises more than 70% of the total solids in comparison with 30% in whole milk the problem of the lactose content in whey powder is more severe. However, since the solubility of lactose is 17 g/100 cm3 H2O at 20°C, it is easy to guide the drying process in such a way that a great part of the lactose can be transformed to the stable a-lactose monohydrate form during the drying process.


Precrystallization and Crystalline Treatment

The basic process layout is modified by conducting a precrystallization before spray drying.

During the precrystallization process, it is easy to keep ideal conditions for crystallization. Viscosity of the concentrate is reasonably low, temperatures may be exactly adjusted and controlled, displacement of used solution from the surface of crystals may be accelerated by agitation, and the required amount of suitable crystals of lactose may be ensured by proper seeding. Furthermore, there is normally time enough for the pre-crystallization process so reaching the theoretical degree of crystallization at this stage is no problem.

The product made by this process is non-caking and, being agglomerated, is dustless and free-flowing. The agglomerates tend to be small and thus the bulk density is relatively high.
The drying chamber with integrated fluid bed, is fitted with pressure-release vents and a fire-extinguishing system. Cyclone, bag filter and external vibrating fluid bed have similar safety features. The cyclone(s) and bag filter may today be replaced b y a sanitary bag filter to improve operating costs.

CHOICE OF WHEY PROCESS
The choice of process depends upon the type of whey available, the intended market for the whey powder and the plant location. The ability to handle sweet whey and yet produce a non-caking product permits use of a simpler layout than if sour whey is to be processed. If the dried powder is intended for dry powder mixes, flowability is essential and the process must be equipped with crystallization and cooling stages to ensure that this property is obtained. Local climate should also be considered. If the climate is too humid, it is advisable to use a process that produces a less hygroscopic product with low caking tendencies.

FRACTIONATION OF WHEY
Instead of producing ordinary or pre crystallised whey powder, it has proven worthwhile where large amount of whey is available to install a ultrafiltration plant The whey is divided into two fractions. A retentate for producing WPC (whey protein concentrates in different grades 35, 60 or 80) or even WPI (whey protein isolates with protein content higher than 90% on solid basis) and a permeate.
The permeate can be evaporated further to produce lactose in different grades. During this process, it is also possible to take out the valuable mineral calcium phosphate.

For the production of whey protein, a standard Tall Form Dryer, TFD with Vibro Fluidizer is used. The atomization takes place by means of nozzle atomization at a pressure of up to 350 bar.

WHEY PRODUCT TEAM
A group of GEA companies have solid experience in whey handling in individual segments such as pretreatment, clarification, fractionation evaporation, spray drying and packing. These companies make up the Whey Product Team. This team's experience can be drawn upon, assisting and advising the installation of a whey treatment line adhering to the client's specification.