Vacuum freeze dryer, which scientists might call lyophilization, uses both a vacuum and a freezing process to remove water from perishable foods and medicines. The result is a product that can be stored at room temperature for years without spoilage, or packed in limited storage spaces and reconstituted with water later. Makers of instant coffee often use a freeze drying process, as do dietitians creating meals for campers, soldiers and astronauts. Freeze drying is also used in the pharmaceutical industry to preserve the integrity of air or moisture-sensitive medicinal compounds.

Drying foods with heat for preservation is an ancient concept, but it has certain drawbacks. The water inside the food is in liquid form, but the heat of the sun or other source slowly converts it to a gas. As the liquid passes out of the food drying equipment, the cell walls are often damaged and the essential flavor and texture of the food is lost. Adding water to foods dehydrated with heat does not always restore flavor or texture. This is why freeze drying has an advantage over heat dehydration in the preservation process.