In our article Introduction to Drying Food: the oldest method of preserving food,we talked about the freeze-drying technique as a special variety of drying method to preserve different kind of food.

What is freeze-drying and when is it used?

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.

The basic process of freeze-drying food was known to the ancient Peruvian Incas of the Andes: the Incas stored their potatoes and other food crops on the mountain heights above Machu Picchu. The cold mountain temperatures freeze the food and the water inside slowly vaporize under the low air pressure of the high altitudes.

Today freeze-dried foods are used especially by astronauts, food manufacturers and the military, but you can also purchase freeze-dried foods for home use.

Here the main advantages of Freeze-Dried Food

• Once the water is removed from foods, they become very light.
• It’s easier and cheaper to transport and delivery a large amounts of freeze-dried food.
• Freeze-dried foods tend to retain most of their nutritional quality, taste, shape and size.
• Freeze-dried foods don’t require refrigeration.
• Freeze-dried foods can last for months or years.
• Freeze-dried foods can also be rehydrated very quickly, unlike dehydrated foods.
• It doesn’t contain bacteria because there’s no water

Here the main disadvantages of Freeze-Dried Food

• The equipment needed for this process is quite expensive
• It’s not so common to know how to use freeze-dried food to prepare meals
• Freeze-dried foods also take up almost as much space as fresh foods

You can rehydrate freeze-dried food using either cold or hot water, so you can carry the food you need. Their long shelf life also makes freeze-dried foods a viable option for emergency food stores.

Source: http://www.livestrong.com/article/509074-advantages-disadvantages-of-freeze-dried-food/