FREEZE-DRYING

Freeze-drying (also known as "lyophilization") is a water removal process that involves freezing the material, then reducing the pressure and adding a low amount of heat to allow the ice in the material to change directly to a vapor (which is called "sublimation").

​

Phase One: Freezing

The material must be frozen below its triple point, which is the temperature and pressure at which solid, liquid, and vapor/gas phases of a particular substance coexist in equilibrium.  It's not enough to get the material super cold, though - it is also important to freeze the material quickly enough to avoid bursting cell walls in materials that are susceptible to cell wall collapse.

 

Phase Two: Drying

This phase can take a while (sometimes up to 36 hours!).  Once Phase One has been completed, our machine then lowers the pressure in the chamber and warms up the trays just enough for the water to sublimate (the ice turns straight into vapor, skipping the liquid phase).  If it gets too warm, the material's structure (and nutrients) could be drastically altered, so it's a very slow and patient process.  A vacuum in the chamber speeds up the sublimation, and the chamber walls provide a surface for the vapor to stick to so that it can turn back into ice.

​

Phase Three: Packaging

Once the machine has dried the materials, it's time to package them.  We operate as quickly as possible, in a room that has been dehumidified, to avoid the materials soaking up any moisture from the air.  Pieces that aren't fully dry will have a drastically reduced shelf life and can "share" moisture with other pieces in the batch, so they need to be removed immediately.