2. OBJECTIVES
• To preserve the biological activity of a product
• To reduce the product weight to lower the
transportation cost
• To extend the shelf life or stability
• To dry thermo labile materials
• To eliminate the need for refrigerated storage
• To get accurate sterile dosing in to the final
product container
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3. PRINCIPLE
• Freeze drying is also known as lyophilization
• lyophilisation is carried out using a simple
principle of physics, sublimation
• Sublimation is the transition of substance from the
solid to the vapor state without passing through an
intermediate liquid phase.
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4. PRINCIPLE
• The entire process is performed at a low
temperature and pressure (usually below the
triple point) by applying vacuum, hence it is
suited for drying of thermolabile compounds
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5. CONSTRUCTION
• A drying chamber in which trays are loaded
• Heat source : radiation source, heating coils
• Vapor condensing or adsorption system
• Vacuum pump or steam ejector or both
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6. CONSTRUCTION
• The distance between subliming surface and
condenser must be less than the mean path of
the molecules
• This increases the rate of drying
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7. CONSTRUCTION
• The temperature of the condenser must be
much lower than the evaporated surface of
frozen substance (to maintain this condition
condenser surface must be cleaned repeatedly)
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8. WORKING
1. Preparation And Pretreatment
2.Prefreezing For Solidifying Water
3.Primary Drying(sublimation Of Ice Under
Vacuum)
4.Secondary Drying(removal Of Residual
Moisture Under High Vacuum)
5.Packing
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9. PREPARATION AND PRETREATMENT
• The solution is pre-concentrated under normal
vacuum tray drying
• This reduces the actual drying by 8-10 times
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10. PRE-FREEZING TO SOLIDIFY WATER
• The sample should be packed in vials,
ampoules, or bottles
• Kept in cold shelves (about-50°c)
• During this stage cabinet is maintained at low
temperature and pressure
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11. PRIMARY DRYING
• After freezing, the product is placed under vacuum.
• Heat is applied to frozen product to accelerate
sublimation
• The temperature and pressure should be below the
triple point of water i.e., 0.0098°c and 0.533kilopascals
for sublimation when water alone is present
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12. PRIMARY DRYING
• Vacuum is applied to the tune of 3mmhg
• The temperature is increased to about 30°c in a
span of 2 hours
• The driving force for sublimation: the
temperature and vapor pressure difference
between evaporating surface and condenser
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13. PRIMARY DRYING
• This enables the frozen solvent in the product
to vaporize without passing through liquid
phase, a process known as sublimation
• Easily removes moisture up to 98% to 99%
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14. SECONDARY DRYING
• Removal of residual moisture under high
vacuum .
• The temperature is raised to 50°c-60°c and
vacuum is lowered about 50mmhg
• Bound water is removed
• Rate of drying is slow
• It takes about 10-20 hrs
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15. PACKING
• After vacuum is replaced by inert gas, the
bottles and vials are closed
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16. CHARACTERISTICS OF FREEZE DRIED
PRODUCT
• Sufficient strength
• Uniform color
• Sufficiently dry
• Sufficiently porous
• Sterile
• Free of pyrogens and particulates
• Chemically stable both in dry and
reconstitution
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17. ADVANTAGES
Removal of water at low temperature
Thermo labile materials can be dried
Compatible with aseptic operations
Sterility can be maintained
Reconstitution is easy
Loss of volatile material is less
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18. DISADVANTAGES
The product is prone to oxidation due to high
porosity and large surface area
Cost may be an issue depending on the product
Long time process
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19. USES
• Used for drying
blood plasma and fractionated products
bacterial and viral cultures
human tissues
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