DAIRY TECHNOLOGY

2. TOPIC
SPRAY DRYING OF
MILK

3. SPRAY DRYING
Spray drying is a method of producing a dry powder from a liquid or slurry by
rapidly drying with a hot gas

6. Collection
 Milk is mostly collected in insulated tankers transferred to processing units
 Raw milk on arrival at the factory is rapid tested for
 Temperature
 Hygiene
 Antibiotics
 Water addition
 Adulteration
 On acceptance
 The milk is pumped into a silo storage tank at the processing plant
 Held at temperatures below 7 C and usually below 5 C.

7. Separation & Standardization
 In Preheating, standardized milk is heated to temperatures between 75 and 120C
 For a specified time
 Preheating causing
 Denaturation of whey protein
 Destroys bacteria
 Inactivates enzymes

8. Pasteurization
 The milk is high temperature short-time pasteurized (HTST) by
 Heating at 72 C for 15 seconds

9. Preheating
 In Preheating, standardized milk is heated to temperatures between 75 and 120C
 For a specified time
 Preheating causing
 Denaturation of whey protein
 Destroys bacteria
 Inactivates enzymes

10. Evaporation
 Boiling the milk under a vacuum at temperatures below 72C in a falling film on the inside of
vertical tubes, and removing the water as vapor
 For spray drying, milk is concentrated to 40-50%

11. Homogenization
 It is not mandatory.
 During homogenization free fat is transformed into globules due to protein
adsorption.
 Pressure is 5-15 MPa
 Homogenization of highly concentrated milk (more than 3:1) destabilizes protein
and decreases powder solubility.

12. Heating
 Before entering the drying chamber
 Concentrated milk feed is slightly heated
 To reduce its viscosity
 To increase the energy available for drying

13. Air Filtration
 Air filter is used to prevent contamination due to dust or any other particulate
matter

14. Feed Pump
 Three piston pump with pressures upto 300-400 bar is used for pumping feed

15. Atomization
 Atomization of the concentrated milk is the principle of the spray drying process
 The atomizer may be either
 A pressure nozzle or
 A centrifugal disc

16. CONTINUE...
 By atomization the concentrate is converted into droplets of size10-200 um, with
the greatest portion in the range 40-80um
 The concentrate is converted into droplets of size10-200 um
 With the greatest portion in the range 40-80um

17. Drying Chamber
 Concentrated milk feed comes in contact with hot air here and is dried
 Co-current flow of hot air is preferred
 By controlling the size of the droplets,
 The air temperature
 And the airflow
 It is possible to evaporate almost all the moisture while exposing the solids to
relatively low temperatures
 External hammers are used on the cone to avoid buildup of dried particles

18. Cyclone Separator
 The principle of cyclone separation is based on the centrifugal force exerted on
a particle
 It separates particles based on their density. Fines are sent forward to the filters.

19. PACKAGING AND STORAGE
 Milk powders are immensely more stable than fresh milk but protection from
moisture
 Milk powder is packed into either plastic-lined multi-wall bags

21. APPLICATIONS
 Food: Milk powder, coffee, tea, eggs, cereal, spices, flavorings, blood, starch and
starch derivatives, vitamins, enzymes, stevia, colorings , animal feed, etc.
 Pharmaceutical: Antibiotics, medical ingredients , additives
 Industrial: Paint pigments, ceramic materials, catalyst supports, microalgae