The Freeze Drying Process

Get to grips with the wonderful process of freeze drying with our basics guide

How does the process work?

Freeze-drying is the only way that water can be successfully removed from an organic substance and many other materials without damage to the cell structure and loss of volatile components.

This entails freezing the substance or item, thereby separating out the water as ice crystals, and then under vacuum, introducing controlled heat. This causes the ice to sublimate, slowly coming away as vapour, without actually melting. Eventually the ice will all have vaporised, leaving the material completely dry, resulting in the minimum of change to the cell structure, extra cellular matrix or chemical composition.

The process also requires a condensing surface that is at a lower temperature than the material being dried for the vapour to migrate to. This is usually an area of the machine that is below -50°C and can be as low as -80°C. The vapour turns back to ice as it condenses on the colder surface and is not drawn into the vacuum pump.

So there you have it a purpose built machine costing many thousand's of pounds just to freeze dry and preserve flowers in.