Milk is collected and tested before being stored in silos at the processing plant. It is then standardized, preheated to destroy bacteria and enzymes, and high temperature pasteurized. The milk is evaporated and concentrated to 40-50% before being homogenized and slightly heated. It is pumped at high pressure through an atomizer to create droplets that are dried in a chamber by hot air. The dried powder is separated and packaged in multi-wall bags for storage. Spray dried milk powder has applications in foods, pharmaceuticals, and various industries.

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