Freeze-dried vegetables are those which have been frozen and then had all of the water removed from them. This allows them to be stored for long periods without the need for refrigeration. This method of preservation is popular for foods designed for long term storage, such as food intended for emergency preparedness. It is also used to create camping foods that are both easy to carry and simple to prepare.
Although almost any kind of vegetable can be made into freeze-dried vegetables, some types are generally more popular and more commonly prepared this way than others. Potatoes, carrots, corn and onions are often freeze-dried. Other popular choices are peppers, peas and green beans. Still other kinds of freeze-dried vegetables are readily available from different suppliers, and it is possible to find almost anything by shopping around.
The shelf life of freeze-dried vegetables varies greatly by brand, generally due to the process used to package the foods. The process of freeze-drying eliminates most of the potential spoilers of stored food, such as insects and bacteria, but freeze-drying alone does not protect quality over long periods of time. When the food is exposed to oxygen, even in small amounts, the food will begin to degrade.
Removing all oxygen from the packaging is the best way to preserve freeze-dried vegetables and other foods intended for long-term storage. By eliminating the oxygen, the quality and safety of the food is preserved for extended periods of time. This problem is tackled in two main ways.
The first way that freeze-dried vegetables are prepared for long term storage is by the addition of a product that absorbs oxygen. This product is placed in the can along with the food, and it acts to neutralize any oxygen that seeps into the can over time. The container is vacuum-sealed and the oxygen-absorbing material will work to protect the food for an extended length of time, usually about 10 years. After that point it cannot absorb any more oxygen and the food will begin to degrade.
To store freeze-dried vegetables for a much longer period of time, nitrogen flushing is typically used. This process requires that the cans and the foods they contain be filled with nitrogen before being sealed. The nature of nitrogen is such that it creates a positive internal pressure. What this means is that the nitrogen inside the can pushes outward just slightly, making it so that oxygen doesn’t enter. This results in foods that can be stored as long as 30 years and still retain their texture, color and flavor.