Whey Products - All types of whey can be spray-dried. Each, however,
requires its own handling techniques.
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 by 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. T
his team's experience can be drawn upon, assisting and advising the
installation of a whey treatment line adhering to the client's specification.