Freeze-drying, also called lyophilization, is a process where food is quickly frozen, and then the ice is turned into water vapor and removed by placing the frozen food in a vacuum, resulting in a dehydrated product. Freeze-drying food requires special equipment, so people do not usually do this at home, instead purchasing products from companies that specialize in this process.
Freeze-dried foods are used by astronauts, campers, backpackers, food manufacturers and the military. You can also purchase freeze-dried foods for home use. Examples include the fruit pieces found in some cereals and astronaut ice cream found in gift shops. You can find entire meals in freeze-dried form, as almost all foods can be freeze-dried.
Once the water is removed from foods, they become very light. This makes for easier portability of large amounts of food and cheaper transportation of the food. Freeze-dried foods tend to retain most of their nutritional quality, taste, shape and size. They do not require refrigeration, and can last for months or years. Freeze-dried foods can also be rehydrated very quickly, unlike dehydrated foods.
The main disadvantage of freeze-dried foods is that they are quite expensive due to the specialized equipment needed for this process. Freeze-dried foods also take up almost as much space as fresh foods, while dehydrated foods take up less space. Unfortunately, many people do not know how to use freeze-dried foods to prepare meals at home.
Although expensive, freeze-dried foods can come in quite handy. You can rehydrate them using either cold or hot water, so you can carry the food you need without worrying about having a way to keep the food cold or to heat it up. Their long shelf life also makes freeze-dried foods a viable option for emergency food stores.