28-09-2012, 01:58 PM
FREEZE DRYING
FREEZE DRYING MACHINE.ppt (Size: 458.5 KB / Downloads: 65)
INTRODUCTION
Freeze drying is the process in which water is removed from a product after it is frozen and placed under a vacuum allowing the ice to change directly from solid to vapor without passing through a liquid phase
WHY WE USE FREEZE DRYING
Removing water keeps food from spoiling for a long period of time
Freeze drying significantly reduces the weight of the food
FREEZING
During the freezing phase the goal is to freeze the mobile water of the product
The rate of cooling will influence the structure of the frozen matrix
Another important term related to freezing is eutectic point
PRIMARY DRYING
In this phase the chamber pressure is reduced and heat is applied to cause the frozen mobile water to sublime
It is important to control the drying rate and heating rate during this phase
WORKING PRINCIPLE
Mainly the freeze dryer consists of 3 parts
Freeze drying chamber
Refrigeration coils
Vacuum pump
Place the material to be preserved on the shelf when it is still unfrozen.
Seal the chamber and process begins.
Compressor lowers the temp and freezes the material and water is seperated.
Vacuum pump forces air out of chamber and lowers the atmospheric pressure to 0.06 atm.
Small heat applied for ice to change phase.
Due to low pressure ice turns directly to water vapour and it flows out of chamber.
Water vapour condenses in freezing coil to solid ice.
Process continues till material dries out.
ADVANTAGES
Preserves color, aroma, taste, shape.
Transportation doesn’t require freezers.
Last long.
Easy packing.
Provide high quality product.
DISADVANTAGES
Increased handling and processing time.
Very costlier process.
Fire hazards if the chamber is not in proper vacuum, while heater is on.
CONCLUSION
The process is much cheaper for pharmaceuticals.
Cost mainly depends on engineering skills and techniques.
Quality of the product is very high.