Freeze drying food is a way of preserving food by removing any liquid content. While the process does involve freezing, food that is freeze dried can be stored at room temperature. It needs to be kept in a sealed container so no moisture gets absorbed back into the product.
The art of freeze drying or lyophilisation has been around since the beginning of the last century. Products are frozen and then the liquid is directly transformed into a gas. This is done by putting the object into an air tight chamber and freezing it. Then the air is removed from the chamber using a vacuum. After that some heat is slowly applied. The removal of the air from the chamber allows the water to transform directly into a gas. This gas then leaves the product and passes over the refrigeration coils freezing on the coils.
Freeze drying is superior to other preservation methods because it preserves the structure of the food and generally does not change the taste. However, there are a few exceptions, for example vinegar does not stand up well to freeze drying. Once the food is ready to be eaten all that needs to be done is add water.
Freeze dried food is popular among survivalists due to its long shelf life. For this reason, it is also used by NASA to provide food to the International Space Station. Also, the military uses freeze dried food to make MRE’s, the food they take out on the field. Backpackers are another group of people that find this food attractive, mainly because freeze dried food has an added benefit in that it is lighter than regular food.
Besides food preservation freeze drying is used in other industries such as drug manufacturing. It is used to prevent various chemicals from degrading and therefore increasing the shelf life of the drugs. It has been tried with less success in restoring documents that have been water damaged. However, this has not always been successful since it is ineffective in restoring inks that run when water is introduced.
Freeze drying is not the same as dehydrating. In dehydrating food is dried out using heat However, some water is left behind since not all of the product can be exposed to air which is necessary for evaporation. This process does help preserve food but does not provide the shelf life that freeze drying does since bacteria will eventually grow even in a little water Also, unlike freeze drying, dehydration can change the taste of food since heat changes the composition of the molecules in food.
In conclusion, if you are looking for a way to preserve food, consider freeze drying.