Originally produced for the U.S. Military and NASA, freeze-dried food has several advantages over frozen or dehydrated foods. Frozen foods retain flavor and nutritional value, but require low temperature storage conditions. Dehydrated/canned foods are shelf-stable, but lose flavor, texture and nutritional content. Freeze-drying is the best of both worlds, preserving freshness, color, and aroma, while being completely shelf-stable.

more about freeze drying

If a freeze-dried substance is sealed to prevent the reabsorption of moisture, the substance may be stored at room temperature without refrigeration, and be protected against spoilage for many years. Preservation is possible because the greatly reduced water content inhibits the action of microorganisms and enzymes that would normally spoil or degrade the substance.

Freeze-drying also causes less damage to the substance than other dehydration methods using higher temperatures. Freeze-drying does not usually cause shrinkage or toughening of the material being dried. In addition, flavors, smells and nutritional content generally remain unchanged, making the process popular for preserving food.

Freeze-dried products can be rehydrated (reconstituted) much more quickly and easily because the process leaves microscopic pores. The pores are created by the ice crystals that sublimate, leaving gaps or pores in their place.