SPRAY DRYING IN MILK PROCESS

DAIRY TECHNOLOGY

1. TOPIC

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

3. 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.

4. 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

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

6. 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

7. Evaporation B oiling 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%

8. 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.

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

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

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

12. 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

13. 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

14. 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 A nd the airflow I t 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

15. 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.

16. 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

17. 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