It’s better without water!
In the days before refrigerators and freezers, people already preserved their food. The oldest method is probably drying. Fresh foods such as fruit were left to dry in the sun and were then available deep into the winter and beyond. The shelf life was guaranteed, because water is not only the basis of life, but also of perdition. The water contained in the food contains bacteria, fungi or chemically particularly active substances such as enzymes that make the food go bad. These decay, processes are dependent on water, similar to the processes in a living cell.
An optimization and acceleration of the drying process occurs when the food is heated. Modern technologies such as the freeze-drying process also known as lyophilization or sublimation drying, as well as vacuum evaporation, today ensure an enormously long shelf life. These preservation methods are the basis of many food products and are also used for emergency food products.
Good examples for daily use are coffee powder and packet soups. Freeze-drying is also the basis of shelf life here. Quickly infused with hot water and the original condition is restored. The drinks and food are ready to enjoy.
But how does freeze-drying actually work?
Foodstuffs that undergo a freeze-drying process are subject to strict controls and official supervision. Only the best quality is used. The freeze-drying process itself consists of several stages.
To preserve fresh color, taste and nutritional values, fresh or cooked food is shock frozen.
Afterwards they are dried in frozen condition at extreme vacuum near the vacuum.
The escaping water vapor is deposited on an even colder cooling surface in the vacuum chamber. This so-called condenser simultaneously ensures that the air in the freeze-drying plant remains dry. In an extremely dry environment, the water evaporates directly from the ice without first becoming liquid. However, this sublimation takes place very slowly, much slower than, for example, boiling water evaporates. Freeze-drying reduces the water content of food to a few percent.
Now the food and dishes are ready for packaging in air- and watertight Tins. During filling, the oxygen contained in the Tins is replaced by nitrogen. Once the Tins are sealed, the high quality of the food is guaranteed for a long time. This delays the decay, sometimes for years, without the need for additional cooling or chemical post-treatment.
Reversing the process is easy
After opening the tins it is enough to add hot or cold water and the original condition is restored. The food is ready to eat after a short time without losing its taste or nutrients.