How does the freeze-drying process work?
Freeze-drying foods is an effective way of removing almost 100% of the moisture from foods, extending its potential shelf life whilst simultaneously maintaining its nutritional composition.
Essentially there are three stages to the freeze-drying process and each stage must be strictly controlled in order to ensure that the physical form of the food and its composition are maintained.
The freeze-drying process works by by freezing the food, then increasing the heat and reducing the pressure in order to allow the frozen water in the food to change directly to a vapor; a process known as sublimation. Finally during the secondary drying stage the temperature is raised further in order remove the ionically bound water particles, reducing the moisture level further.
The majority of foods can bring their moisture levels down to under 2% through this process.
Freeze-drying can be seen as similar to placing the food into a state of suspended animation and so once rehydrated the food is as fresh and nutritious as it was the moment it was frozen - and as long as the food is adequately protected from moisture contamination, the food can be stored for extremely long periods of time without any degradation in flavour, texture, colour, aroma or nutritional composition.