A. Principle:
Freeze drying works by a process
known as sublimation which occurs when a product is taken from a frozen to a
gaseous state, bypassing the liquid stage. Freeze drier creates an optimal
environment for sublimation to occur by combining a refrigeration system with a
vacuum system. The vacuum system creates nearly a pressure free environment to
allow the vapour from the frozen product to easily flow towards the cold
condenser surface. The glassware containing the frozen product is exposed to
room temperature which drives the process by adding heat. This causes the
frozen product to sublimate and then freeze on the colder surface of the
condenser walls.
Freeze drying is used as a
preservative or processing technique for a wide variety of products that are
biologically or chemically active at normal temperatures, subjected to physical degradation and that require long
term storage at room temperature above freezing condition.
B. Method :
1.Check all valves, drain plugs,
doors & covers. Check that line voltage is correct for the equipment (
Sentry point Lv )
2.Switch on Refrigerator &
wait until condenser status light indicates "OK" before proceeding.
3.Solidify prefreeze product to
atleast - 40 0C.
4.Turn on vacuum & wait until
vacuum status light indicates "OK" before proceeding.
5.Connect pre-frozen product
containers one at a time to a manifold valve and apply vacuum and allow freeze
drying of sample to be completed.
6.Remove flask from manifold valve
after turning vacuum knob.
7.To Shut down ; release vacuum in
system.
8.Switch off vacuum pump.
9.Remove product.
10.Switch off refrigeration.
Defrost, drain & clean condenser.
Check vacuum pump oil level & clarity. Change or add as needed.