Freeze-dried food
Technology -

24.12.2004

Freeze-dried dish before and after hydration

Freeze-drying is a process of dehydration of substance by freezing it, and afterwards the sublimation of ice crystals. Sublimation means converting ice in vacuum from the solid state directly to vapour by heat. This way freeze-dried food is prepared; as well as some ingredients used in food industry.

It is possible to freeze-dry any food product – vegetables, meats, fruits, mushrooms, fish, cheese or yoghurts. The process of freeze-drying removes almost 100% of the water they contain. That is why they become very light, what makes them perfect for a racing yacht, canoe, bike trip or expedition into high mountains where
each kilogram of weight is important.

Products dehydrated become very crisp and feel like light Styrofoam. For example, freeze-dried fruit, which you can eat after hydration, is great dry as well- just like fruit chips.

The interesting thing is how dinner dishes are prepared this way. First the dish is prepared in a traditional way, using the best quality ingredients - e.g. meat must be very lean, as freeze-drying does not perform very well on fat, and fat gets bad quickly. After the dish is ready, all of its components (rice, buckwheat groats, noodles, meat or vegetables) are separated from each other, as they have to be freeze-dried in different conditions (temperature and pressure).

In the freeze-drying process all products loose water, keeping their taste, smell, vitamins, proteins and minerals as well as colour and shape. Research has proven freeze-drying reduces the amount of bacteria in food products. Minor water content of a few percent allows long storage of products. Well kept cell structure permits fast hydration.

Food prepared this way is packed in hermetic bags. This way it can be stored for a long time. It is impossible to give the expiry date, because the product in its original package cannot go bad or loose its nutrition. Freeze-dried food can survive in any condition – damp, high and low temperatures – keeping its nutrition and taste.

Preparing the food for eating takes only minutes. Just put the dry product in a bowl, add hot water and wait a few minutes as all components are hydrated and soft. After hydration the dish is tasty and nutritious. Often, to save on washing up, member of extreme expeditions have added water to the bags, and ate food directly from them.