Freeze Drying 101
Freeze-drying, explained simply.
Freeze-drying is a food preservation method that removes moisture from food after it has been frozen. The food is first frozen and then placed under low pressure. The frozen water turns directly into vapour and is removed from the food.
The result is a lightweight, dry product that can be stored for longer when properly packaged and stored.
The four-part process
How does freeze-drying work?
Freeze
The prepared food is frozen at a low temperature.
Dry
The frozen moisture is removed under low pressure.
Pack
The dried food is sealed in protective packaging.
Rehydrate
Water is added when you're ready to eat the meal.
That's freeze-drying in four simple steps.
Why it matters
Why remove the moisture?
Moisture plays an important role in food spoilage. Removing much of the moisture helps create a food product that can be stored without refrigeration when properly packaged and stored.
It also makes the food much lighter, which is one reason freeze-dried food is useful for travel.
A useful distinction
Freeze-drying vs dehydration
They're similar, but they're not the same.
Dehydration
Uses heat to remove moisture from food.
Freeze-Drying
Freezes the food first and then removes the frozen moisture under low pressure.
Because the processes are different, the resulting food can also differ in texture, appearance and rehydration.
The result
What happens to food during freeze-drying?
Weight
A large amount of the food's water is removed, making it considerably lighter.
Texture
The structure of the food changes during drying. Once rehydrated properly, much of the original eating experience can return, although it may not be identical to freshly cooked food.
Taste
Freeze-drying is designed to preserve the food's flavour, which is why it works well for preserving familiar meals.
Nutrition
Freeze-drying can help retain much of the nutritional value of food, although some nutrients can be affected during processing.