Freeze drying removes moisture from food through sublimation, which turns water molecules into vapor. Freeze drying food affects its texture more than other preservation methods, like canning or freezing, but the nutritional value and flavor stay intact. Since freeze dried food is so light, it’s great for taking on backpacking trips or storing in your emergency preparedness kit.

Freeze-drying—technically known as lyophilisation, lyophilization, or cryodesiccation—is a dehydration process typically used to preserve a perishable material or make the material more convenient for transport. Freeze-drying works by freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to the gas phase.

Engineering ideas

• sublimation, water vapor, texture, preservation, nutritional value, flavor, dehydration, freezing, solid, gas

Do It
Challenges for you to work on…

• astronaut food – find some examples of food that has been taken to space for astronauts to eat. Does this sound tasty?