The origins of freeze drying can be traced back to the 15th century, where a rudimentary form of freeze drying was used by the Incas. Their crops were stored on the mountain heights above Machu Picchu where the cold mountain temperatures froze their food stores, and the water inside slowly vaporized under the low air pressure of the high mountain altitudes.

Modern freeze-drying techniques were initially developed during World War 2 to conserve blood sent to Europe from the US for medical treatment of the wounded. Shortly thereafter, the freeze-dry process was applied to penicillin and bone, and freeze-drying became recognized as an important technique for the preservation of biologicals.

Since that time, freeze-drying has been used as a preservation or processing technique for a wide variety of applications to include food, pharmaceuticals, restoration of water damaged materials, ceramics, and many others. Freeze-dried foods are closest to their natural composition with respect to structure and chemistry, ensuring essential vitamins and nutrients are maintained. The freeze-drying process became widely popular when it was used by NASA in the creation of freeze-dried ice cream, a popular astronaut food. It is also widely used to produce essences or food flavourings.

The Food Freeze Drying Process

Food products are frozen and then placed in a vacuum chamber. The Vacuum pump connected to the chamber is started and it applies a high vacuum to the chamber. Under the high vacuum conditions in the chamber, evaporation of moisture occurs without thawing or melting of the food item. This process is known as lyophilization. The vapour collects on a condenser inside the vacuum chamber and re-freezes. The condenser is defrosted at the end of the cycle. The Freeze Drying process retains the physical structure and properties of the food product and preserves them for re-hydration or further processing at a later date.

Advantages of Freeze Drying Food

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 have a major disadvantage. The high temperatures used cause chemical and physical changes as well as loss of nutrients. Changes in taste and texture of a food product could make it inedible or undesirable.

Food Types Suitable For Freeze Drying

• Fruit and juice
• Vegetables
• Meats
• Fish and Seafood
• Eggs
• Dairy
• Coffee

More on freeze dried food

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 may need to diced or sliced first to be freeze dried economically. This also applies to meat; small chunks of meat freeze dry well, but larger fillets need to be sliced first. Meat and seafood can be cooked before freeze drying if required.  There are some foods where freeze drying is not cost-effective.

Sizing and Selecting a Freeze Drying Machine

The Freeze Dryer comprises 3 major components

1. Vacuum chamber. The vacuum chamber is equipped with heated shelves to accommodate the food to be dried. The Shelf area will determine the size of the load to be dried in a single cycle.
2. Ice Condenser. The condenser is sized to trap all the vapour extracted from the food. The condenser must be larger enough to handle all the vapour produced in a single cycle.
3. Vacuum Pump. The vacuum pump is sized according to the chamber size. It must provide a fast pump-down and ability to maintain a high vacuum under load.

DYNAVAC has engineered a range of Freeze Dryers capable of all scales of freeze drying, from DIY to full production capacity. Ranging from 1kg to 2500 kg capacities. The name DYNAVAC has been synonymous with freeze drying in Australia since the 1950s. We continue to offer cutting edge solutions to the needs of Australian Freeze Drying customers.