The freeze drying process was first applied to food products after the Second World War, in order to preserve and store foods without the need for refrigeration. Coffee was one of the first freeze dried food products to be produced, but now vegetables, fruits, meats, fish, dairy products, herbs and food flavourings can be successfully freeze dried.
Food Freeze Drying Process
Freeze drying food uses a process called lyophilization to lower the temperature of the product to below freezing, and then a high-pressure vacuum is applied to extract the water in the form of vapour. The vapour collects on a condenser, turns back to ice and is removed. Finally, a gradual temperature rise extracts all remaining 'bound' moisture from the product. This process retains the physical structure of the food product and preserves it for re-hydration at a later date.
Advantages of Freeze Drying Food
With freeze drying, foods and liquids can be dried at low temperatures without damaging their physical structure. Freeze-dried foods don’t need to be refrigerated or preserved with chemicals and can be reconstituted quickly and easily by adding water.
Conventional drying methods also have a major disadvantage as the high temperatures used can cause chemical or physical changes. Changing the taste or texture of a food product could make it inedible or less palatable which would be very undesirable.
Food Types Suitable For Freeze Drying
- Fruit and juice
- Fish and Seafood
Cuddon freeze dryers are very popular in the production of freeze dried food. Freeze dried food is lighter and more compact, making it ideal for situations where space is at a premium.
Freeze dried food can be used for:
- Backpacking and camping
- Mountaineering and hiking
- Military rations
- Survival food storage
- Space exploration
Typical Freeze Dried Food
- Instant foods such as noodles and powdered soups
- Ready meals such as bolognaise, stroganoff etc.
- Seafood such as mussels
- Fruit in breakfast cereals
- Fruit juices and instant coffee
- Extracts from blackcurrants and other fruits
- Ice cream
- Culinary herbs
- Extracts from cows’ milk used in baby formulas
Some foods freeze dry very well, but not all food is suitable for freeze drying. Small fruits and vegetables can be easily freeze dried, whereas whole fruits and large vegetables would not be suitable, although they can be freeze dried if cut into small pieces first. This also applies to meat; small chunks of meat freeze dries well, but larger fillets need to be cut into pieces. Meat and seafood also require cooking before freeze drying. For some foods freeze drying is not cost-effective.