The document discusses various drying technologies used in the dairy industry. It describes spray drying, drum drying, freeze drying, and foam mat drying. Spray drying involves atomizing milk concentrate into a heated chamber to evaporate water quickly into a powder. Drum drying applies milk to a heated drum to dry into flakes. Freeze drying freezes and then sublimates water to preserve nutrients. Foam mat drying forms a stable foam to increase surface area for drying at low temperatures. Drying removes water, improves shelf life, and makes transportation and packaging easier.

1. KAMDHENU UNIVERSITY
College of Dairy Science
Amreli
Topic :- Drying Technology
kishor jadav

2. Drying means……
 Drying is commonly the last stage in a manufacture process.
 Drying is the final removal of water from material.
 Drying: the removal of all or most of the liquid by supplying latent heat
to cause thermal vaporization.
 Most pharmaceutical materials are not completely free from moisture
but contain some residual water, which may vary with the temperature
and humidity

3. Why we use drying???
 Drying makes materials more convenient in
 Packaging,
 Transporting,
 Preserving,
 Improves quality of products.

4. Drying curve

5. DIFFERENT TYPES OF DRYING
Spray Drying
• Pasteurized milk is first concentrated in
an evaporator to approximately 50% milk
solids. The resulting concentrated milk is
then sprayed into a heated chamber
the water almost instantly evaporates,
leaving fine particles of powdered milk
solids.
Drum Drying
• Milk is applied as a thin film to the
surface of a heated drum, and the dried
milk solids are then scraped off.
powdered milk made this way tends to
have a cooked flavor, due
to caramelization caused by greater heat
exposure.
Freeze Drying
• Same as drum drying
but involves freezing
which retains more
amount of nutrition.

6. Spray drying
Spray drying involves atomising the milk
concentrate from the evaporator into fine droplets.
Done inside a large drying chamber in a flow of hot
air (up to 200˚C) using either a spinning disk
atomiser or a series of high pressure nozzles.
The milk droplets are cooled by evaporation and
they never reach the temperature of the air.

7. Contd….
The concentrate may be heated prior to atomisation to
reduce its viscosity and to increase the energy available
for drying.
The remaining water is evaporated in the drying
chamber, leaving a fine powder of around 6% moisture
content with a mean particle size typically of < 0.1 mm
diameter.
Secondary drying takes place in a fluid bed, or in a
series of such beds, in which hot air is blown through a
layer of fluidised powder removing water to give
product with a moisture content of 2-4%.

8. SPRAY DRYER
The spray dryer provides a large surface area for heat
and mass transfer by atomizing the liquid to small
droplets.
These are sprayed into a stream of hot air, so that each
droplet dries to a solid particle.
The drying chamber resembles the cyclone ensuring
good circulation of air, to facilitate heat and mass transfer,
and that dried particles are separated by the centrifugal
action.
Spray dryer can be operated efficiently at various feed
rates.

9. Essential Processes
Heating of the air
Atomizing the concentrate in the air
Mixing hot air and atomized liquid
Separating powder and consumed drying air
Aggregation of powder particles

10. SPRAY DRYER

11. SPRAY DRIER NOZZLE ROTARY SPTAY NOZZLE

12. COMPACT SPRAY DRYER
 F:STUDYDairy TechnologyCondesing and DryingCompact-Dryer-GEA-
Niro.exe

13. Advantages of the spray drying process
 The droplets are small, giving a large surface area for heat transfer, so that
evaporation is very rapid.
 The actual drying time of a droplet is only a fraction of a second, and the
overall time in the dryer is only a few seconds.
 Because evaporation is very rapid, the droplets do not attain a high
temperature, most of the heat being used as latent heat of vaporization.
 The characteristic particle form gives the product a high bulk density and, in
turn, ready solubility.
 The powder will have a uniform and controllable particle size.

14. Contd….
 The product is free-flowing, with almost spherical particles, and is
especially convenient for tablet manufacture.
 Labour costs are low, the process yielding a dry, free-flowing powder from
a dilute solution, in a single operation with no handling.
 It is possible to operate spray driers aseptically using heated filtered air
to dry products such as serum hydrolysate.

15. Disadvantages
The equipment is very bulky, connected to
accessories, fans, heaters.
 That is make it expensive.

16. Drum Dryer (Film Drying)
 Milk or milk products can be dried in a thin film (~ 0.1 mm)
on an internally steam heated rotating drum.
 Often, two drums are set up side by side at a very small
distance apart.
 The water evaporates within a few seconds, which is possible
due to the high drying temperature (>100°C).
 On a drum drier, the product enters as a liquid and leaves as
a solid.
 The product is removed from the exterior of the drum by a
"doctor" blade. The dried film is scraped off from the drum
by means of a steel knife, collected, and ground.

17.  The major disadvantage of drum drying is that the dry
product may have a scorched flavor and solubility is much
lower because of protein denaturation.
 Considerable product damage due to heating occurs, mainly
because scraping off is always imperfect and, accordingly, a
part of the milk is repeatedly wetted and dried.
 Now a days the roller drying process is little used.
Contd….

18. IN A DRUM DRYER……
 Vacuum: For vacuum drum drying, the vacuum between the drum and
the housing surrounding the drum is maintained at 68.5 to 73.6 cm Hg
vacuum.
 Size & Speed: The drums used for a drier are 61 to 122 cm in diameter,
and up to 3.6 m in length.
 The speed of the drums is adjustable usually being from 6 to 24 rpm;
however, the range of speed may be from 1 to 36 rpm.
 Product Contact: The product is removed after 3/4th to 7/8th of a
revolution of the drum has taken place. The product is in contact with the
drum for about 3 s or less.
 Spacing: The spacing between drums of a double cylinder drier is about
0.05 to 0.1 cm when the drums are cold.

19. DRUM DRIER

20. Advantages of the drum dryer
 The method gives rapid drying, the thin film spread over a large area
resulting in rapid heat and mass transfer.
 The equipment is compact, occupying much less space than other
dryers.
 Heating time is short, being only a few seconds.
 The drum can be enclosed in a vacuum jacket, enabling the
temperature of drying to be reduced.
 The product is obtained in flake form, which is convenient for many
purposes.

21. Freeze Drying
 Freeze drying is a process used to dry extremely heat – sensitive
materials. It allows the drying , without excessive damage, of proteins,
blood products and even microorganisms, which retain a small but
significant viability.
 In this process the initial liquid solution or suspension is frozen, the
pressure above the frozen state is reduced and the water removed by
sublimation.
 Thus a liquid –to-vapour transition takes place, but here three states of
matter involved: liquid to solid, then solid to vapour.

22. Condt….
 Technically known as lyophilisation.
 The food material is placed in a vacuum chamber and frozen
until the water crystallizes. The air pressure is lowered,
creating a partial vacuum, forcing air out of the chamber; next
heat is applied, sublimating the ice; finally a freezing coil traps
the vaporized water.
 Freeze drying, which preserves many nutrients in milk,
compared to drum drying.

23. Advantages
Damage due to heating does not occur but that is
also true of spray drying if skillfully performed.
Suitable for processing in small quantities and is
applied to lactic starters, etc.

24. Disadvantages
The method is expensive.
The fat globules are subject to partial
coalescence; this causes freeze-dried whole
milk powder to show segregation after its
reconstitution. Freeze drying costs about 5 to
10 times the conventional drying for foods.

25. Freeze dryer production type
Loading a freeze dryer

26. Foam mat drying
 Foam-mat drying is one of the simple methods of drying in
which a liquid food concentrate along with a suitable
foaming agent is whipped to form a stable foam and is
subjected to dehydration in the form of a mat of foam at
relatively low temperature .
 Rate of drying in this process is comparatively very high
because of an enormous increase in the liquid-gas interface,
in spite of the fact that the heat transfer is impeded by a
large volume of gas present in the foamed mass.

27. Foam Spray Drying
 Foam spray drying, is new and has caused interest in new
products. Common dairy products, skim milk, whole milk,
buttermilk, sweet and sour cream (up to 3:1 fat to SNF)
 whey and emulsified cheese slurry can be foam spray dried.
 Air is commonly used as the added gas for making foam
spray nonfat dry milk.
 Nitrogen is commonly used for making foam spray dried
whole milk.

28. Thank you…