Cryogenic cooling
Cryogenic cooling in oenology uses carbon dioxide (CO2) to cool the harvest and protect it from oxidation, particularly during cold maceration. CO2 is used in the form of snow or dry ice, which cools the product by sublimating, releasing cold. This process is an alternative to more complex cooling systems. Dry ice require safety measures due to the release of gas.
CO2, in the form of ice or snow, cools the product to be treated by sublimating. The use of this system, which is still marginal, is reserved for initial cold maceration and is an interesting alternative to the heavier installations for cooling the harvest using external heat exchangers.
The dry ice is preferably added at the same time as the grapes, which ensures even cooling of the harvest.
Liquid CO2
Gas tank
Liquid CO2, kept under pressure, releases dry ice and carbon dioxide when it reaches atmospheric pressure. As the snow/gas ratio varies according to temperature and pressure (and therefore the container), the exact quantity of dry ice released is not known. It is packaged in bottles or insulated tanks and can be kept for several months, even if the container is opened.
In a bottle:
At room temperature, it takes around 4 kg of liquid CO2 to produce 1 kg of dry ice, which provides 150 Frigories.The cooling power of liquid CO2 is therefore : 150 / 4 = 37.5 Frig / kg
In a tank:
At room temperature, it takes around 2.5 kg of liquid CO2 to produce 1 kg of dry ice.The cooling capacity of liquid CO2 is therefore : 150 / 4 = 37.5 Frig / kg
Carbonic snow
When the pressure of the liquid CO2 drops below 5.5 bars, the liquid vaporises and turns into carbonic snow.At room temperature, the snow is transformed into carbon dioxide, releasing cold.
The cooling capacity of carbonic snow is : 150 Frig / kg
Dry ice
Dry ice is the compacted form of dry ice . It therefore takes up much less space than dry ice. Stored in an insulated container at minus 80°C (portable if required), it should be consumed within two to three days at most. It comes in the form of sticks, blocks, etc., of varying weights depending on the manufacturer.
The cooling power of dry ice is : 150 Frig / kg
Dry ice
Note : Carbonic snow and dry ice release 500 litres of carbon dioxide per kg !
Safety rules must be observed (ventilation, choice of storage location, etc.).