Freeze drying is a dehydration process used to remove water and lock in color, flavor, and nutrients. Food is frozen to -40° or below and then the atmospheric pressure is reduced to a few milibars. The frozen water in the food sublimates directly from a solid to a gas and is removed.
Removing the water from food makes it much lighter and causes the food to retain its flavor, color, and nutrients. Since there is no water in the food it can be vacuum sealed and preserved for long periods of time without requiring chemicals or preservatives. Many freeze dried foods have a shelf life of 25 years.
Freeze Dry vs. Dehydrate
May people use the terms “freeze dried” and “dehydrated” interchangeably. These are completely different processes. In freeze drying water is removed by freezing the product and then decreasing the atmospheric pressure to remove water. In dehydrating heat is used to remove the water. The heating changes the tasted, characteristics, and nutritional value of the product. Dehydrating can reduce the nutritional value of the food by up to 40%.