ppt OF FREEZE DRYING

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					FREEZE DRYING
          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
PHASES OF FREEZE DRYING
 Freeze drying process consist of three
 phases
           freezing
           primary drying
           secondary drying
            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
    SECONDARY DRYING
The length of the secondary drying
process will be determined by the product
The water content may be carefully
cotrolled
THE FREEZE DRYING PROCESS
    Aspects of food stuffs
    Freezing process
    Drying process
       WORKING PRINCIPLE
 Mainly the freeze
  dryer consists of 3
  parts

     • Freeze drying
       chamber
     • Refrigeration coils
     • Vacuum pump
     WORKING (Contd…)
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.
     WORKING (Contd…)
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.
     WORKING (Contd…)
Sublimation process accelerated to avoid
overheating.
Once dried sufficiently – sealed in
moisture free packages.
As long as package is secure it can sit
without degrading for years and years.
         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.
               USES
In pharmaceutical companies.
Food industries.
In flower industries.
For protecting old books.
         CONCLUSION
The process is much cheaper for
pharmaceuticals.
Cost mainly depends on engineering skills
and techniques.
Quality of the product is very high.
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