Milk is spray dried by atomizing concentrated milk into a hot air stream, causing rapid evaporation of the water and resulting in a fine powder. This process is a common method for preserving milk and other liquids.
Here's a breakdown of the spray drying process:
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Concentration: The milk is typically concentrated first through evaporation to increase the solids content. This makes the drying process more efficient.
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Atomization: The concentrated milk is then atomized into a fine spray of droplets. This is achieved using either:
- Pressure Nozzles: High pressure forces the liquid through a small nozzle, creating a fine spray.
- Centrifugal Discs: A spinning disc flings the liquid outward, atomizing it into droplets.
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Drying: The atomized milk droplets are introduced into a drying chamber where they come into contact with a stream of hot air (typically between 180 – 220 °C). The hot air rapidly evaporates the water from the droplets.
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Separation: The dried milk powder is then separated from the air stream, usually by cyclones or bag filters.
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Packaging: Finally, the milk powder is cooled and packaged to prevent moisture absorption and maintain its quality.
Here's a simple table summarizing the process:
| Step | Description |
|---|---|
| Concentration | Milk is concentrated to increase solids content. |
| Atomization | Concentrated milk is sprayed into fine droplets using nozzles or discs. |
| Drying | Hot air evaporates water from the droplets. |
| Separation | Dried milk powder is separated from the air. |
| Packaging | Milk powder is cooled and packaged. |
Spray drying allows for the production of a shelf-stable milk powder that can be easily reconstituted with water, making it a valuable method for preservation and distribution.
