The first cosmonauts ate food supplied in special tubes, but now that type of packaging is almost never used. Now, the cosmonauts’ larder is more likely to be stocked with preserves and freeze-dried food in vacuum packs — which were introduced in the 1970s.

Soups, purees, cream cheese, fruits, vegetables, meat, fish, grain, kisel (a sweet drink thickened with starch) and juices are normally stored in dehydrated form. The foods are dehydrated and then packaged in vacuum sachets. Meat and fish contain up to 80% water, while fruit and vegetables contain 90%. Removing the water makes these foods much lighter and more compact and can extend their shelf life to several years.

At the beginning of the production cycle the food is prepared in the normal way, and then it is poured or spread out on an oven tray in a 2 cm-thick layer. It is then frozen using liquid nitrogen or another gas in liquid form. The food is kept at a temperature of as low as –50° С for 15-24 hours. In the next stage, the food is sent to a vacuum chamber, where the air pressure is just 1.5 mm Hg. The temperature in the chamber is increased to +50 or even +60° C. In vacuum conditions the frozen water is converted to steam immediately, without passing through the liquid stage. The moisture content is reduced to just a few percent of its normal level. This process vegetable does not harm either plant or animal cells, and they retain most of their nutrients, microelements and vitamins. The natural smell and flavor of the food is also preserved.

No preservatives, flavorings or coloring needs to be added during the freeze drying process. The result is a great reduction in the weight of the food: for example, 50 kilograms of cream cheese is transformed into 12 kilograms of “space cheese”.

The freeze dried food is repackaged into sterile soft packs made of polymer plastics, from which all the air is removed. When in orbit, before eating the cosmonaut needs to pour the necessary quantity of water into the pack (warm water for salads and snacks, hot water for drinks, and first and second courses), mix the contents with the water and wait. After several minutes, the food has rehydrated, and is ready to eat Most of the food eaten by cosmonauts (up to 90%) including freeze dried food, in produced by the Biryulevskiy Experimental Food Plant.