Freeze Drying
By Laura,Irene, Naomi
CONTENTS
01
Definition
02
Process
03
Problems need
t o b e avo i d
04
Application
What is Freeze drying?
Freeze drying (also known as lyophilization) is a
water removal process typically used to
preserve perishable materials, with the goal of
extending their shelf life and/or preparing them
for transport.
History of Freeze drying
Freeze-drying was invented by Jacques-Arsene
d’Arsonval at the College de France in Paris in 1906.
Later, during World War II, it was widely implemented to
preserve blood serum. Since then freeze-drying has become one
of the most important processes for preservation of heatsensitive biological materials.
During the 1950s, industrial freeze-drying of foods began.
Freeze-drying is currently used as a preservation method for
foods and a wide range of other products.
Freeze drying occurs in three phases
1st phrase
Freezing Phrase
2nd phrase
Primary Dring
Phrase
3rd phrease
Secondary
Drying Phrase
Freezing Phrase
·most criticize phase
·done in a freezer, freeze dryer,
shell freezer
·sublimation instead of melting so:
preserves its physical form
·quickest way: using ice crystals
Primary Drying Phrase
·lowed the pressure and added
heat (in order to let water to
sublimate)
·vacuums speed up the process
·cold condenser: water vapor
to adhere and solidify.
·95% water is removed
Secondary Drying Phrase
·ionically-bound water
·molecules are removed
·materials remain in a porous structure
·vacuum broken by inert gas before the
material is sealed
·can be dried to 1-5% residual
moisture
Problems that need to be avoid
Heating the product too high in temperature can cause melt-back or
product collapse
Condenser overload caused by too much vapor hitting the condenser.
• Too much vapor creation
• Too much surface area
• Too small a condenser area
• Insufficient refrigeration
• Vapor choking – the vapor is produced at a rate faster than it can get
through the vapor port, the port between the product chamber and the
condenser, creating an increase in chamber pressure.
More Application
·People also use freeze-drying to preserve
other sorts of material, such as
pharmaceuticals.
·Similarly, research scientists may use freezedrying to preserve biological samples for
long periods of time.
·Freeze-dried roses are growing in
popularity as wedding decorations.
·Restore water-damaged materials, such as
rare and valuable manuscripts.
Thanks for watching!
PPT制作：Naomi, Laura, Irene
资 料 寻 找 ： L a u r a
演讲： Naomi, Laura, Irene