The document discusses a lyophiliser or freeze dryer, which uses a three step process to freeze-dry materials for preservation. The process involves prefreezing the material to form ice crystals, primary drying where heat and low pressure allow water to sublime from the frozen material, and secondary drying to remove remaining bound water molecules. A lyophiliser is commonly used in industries like pharmaceuticals, biotech, diagnostics and tissue culture to dry materials while retaining their porous structure and physical form with minimal residual moisture.

1. LYOPHILISER
Dr Sumitha
J
Associate Professo
r
JBAS College for Women, Chennai-18

2. LYOPHILISER
• Lyophiliser or Freeze Dryer is used to freeze-dry the materials used
mainly for preservation of microbes and other biological material
s
• The principle it operates is the removal of Water from frozen
product
s
• The process has three steps- Prefreezing, Primary drying &
Secondary drying.

4. FREEZING PHASE
• A lyophiliser uses various methods to freeze the product. Freezing is done on a shelf
in the lyophiliser.The lyophiliser cools the material below its triple point to ensure that
sublimation, rather than melting, will occur. This preserves the material’s physical form
.
• A lyophiliser most easily freeze-dries large ice crystals, which can be produced by slow
freezing or annealing.
• However, with biological materials, when crystals are too large they may break the cell
walls, and that leads to less-than-ideal freeze-drying results.To prevent this, the freezing
is done rapidly.
• For materials that tend to precipitate, annealing can be used.This process involves fast
freezing and then raising the product temperature to allow the crystals to grow.

5. PRIMARY DRYING (Sublimation) PHAS
E
A lyophilizer’s second phase is primary drying (sublimation), in which
the pressure is lowered and heat is added to the material in order for
the water to sublimate.
The lyophilizer’s vacuum speeds sublimation.
The lyophilizer’s cold condenser provides a surface for the water
vapour to adhere to and solidify.The condenser also protects the
vacuum pump from the water vapour.
About 95% of the water in the material is removed in this phase.

6. SECONDARY DRYING (Adsorption) PHASE
A lyophilizer’s
fi
nal phase is secondary drying (adsorption), during which the
ionically-bound water molecules are removed.
By raising the temperature higher than in the primary drying phase, the bonds are
broken between the material and the water molecules
.
Freeze-dried materials retain a porous structure. After the lyophilizer completes its
process, the vacuum can be broken with an inert gas before the material is
sealed.
Most materials can be dried to 1-5% residual moisture
.

7. Applications of Freeze-Dryer
Pharmaceutical
s
Biotech Industr
y
Diagnostic
s
Tissue Cultur
e
Nanotechnolog
y
Nutraceutical
s