01
the story
The origins of freeze-drying
Humankind has been looking for ways to preserve certain products, especially food products, for many thousands of years.
A technique resembling freeze-drying was first employed on 13th century in Peru, where the Incas, who lived on the high plateaus of the Andes, would expose their food to the cold overnight before leaving it out to dry in the sun the following day. The low atmospheric pressure of the Peruvian Highlands was conducive to the sublimation of water and the preservation of food. The Vikings also attempted to freeze-dry herring, but this process failed due to the low altitude.
The freeze-drying process as we know it was actually invented in 1906 by two French researchers at the Collège de France, Arsène D'Arsonval and Frédéric Bordas, but it was not until 1943 that the term freeze-drying was proposed by Professor Alexander Fleming.
02
The technique
The principle of freeze-drying
Freeze-drying is a cold drying technique which consists in extracting water from a product to make it stable and easier to handle and to extend its shelf life.
Several steps are required :
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- The first step is to freeze the product between -30°C and -50°C, transforming the water present into ice.
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- The ice is then sublimated, i.e. transformed into a gaseous state (water vapour), in a vacuum set to -20°C.
- The final phase is known as ‘final drying,’ a drying process carried out at +37°C to extract all residual water from the product.
Freeze-drying results in dehydrated products with a low moisture content of 1-2%.