8. Freeze  Drying  ( Lyophylization )


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.