Lyophilization, also called freeze drying, is by far the gentlest product drying method. It is based on the physical phenomenon of sublimation, which means a direct transition from the solid state to the vapour state without passing through the liquid state. The frozen products are dried under vacuum without thawing. This method offers a wide spectrum of potential applications:
- For preserving the characteristics of the original substances (e.g. pharmaceutical products or coffee)
- For preserving the original form (e.g. animal preparations, archaeological objects, flowers or books)
- For conditioning the material (e.g. freeze-dried fruit in yoghurt)
- For the sample preparation for chemical or biochemical analysis (e.g. investigation of trace elements in foods, sludge or soil)
Freeze dryers are generally divided into two categories: those for batch operation and those for continuous operation. Systems for batch operation are commercially available with capacities from 2 kg to approximately 1 tonne per drying cycle. Christ focuses on this product segment and is the only manufacturer in the world that covers the full spectrum from standard laboratory units over pilot freeze dryers to large production machines.