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Gas flushing, storage under gas
Gas flushing is a process in which products are stored in an artificially produced atmosphere, normally within a plastic container such as a hermetically sealed tray or pouch. The process is also referred to as MAP or Modified Atmosphere Packaging, and is used to enhance colourretention of, for example, fresh meat or cured meats such as bacon and cooked ham, especially in sliced form. Storage with inert gas is applied to wines in tanks, in order to preserve an adequate CO2
content in the wine, and their organoleptic qualities, to protect them from oxidation, and to prevent bacterial deviations in place of the use of sulphur dioxide (SO2
). This technique is above all applied to white wines, rosés and red primeurs. It also allows one to prevent the alteration of tanks which would be emptied, for example in the case of bulk sale to private individuals. Finally, it permits the conservation of sterile fruit juices.
Field of application
Gas flushing is mainly used for meat and meat products is also used for others products, such as bakery products.
Techniques, methods and equipment
a) Gas flushing
The gas mixtures used will vary depending on whether the meat to be protected is fresh or cured. The desirable bright red colour of fresh meat can be prolonged by storage in an atmosphere with some oxygen, whereas the purple-red colour of uncooked cured meat and the pink colour of cooked cured meat is better preserved in an atmosphere completely free of oxygen. In all types of meat or meat products, gas mixtures are used which also contain carbon dioxide (CO2
). This inhibits bacterial growth on the meat and marginally extends the storage life.
Normal air contains:
Nitrogen 78%, Oxygen 21%, and CO2
less than 1%.
In comparison, typical gas mixes for use with meats and meat products are:
Another use of gas is the use of solid CO2
, usually in pellet form, which is added to meat during comminution. This has the effect of rapidly reducing the temperature of the meat mixture and creating a “blanket” of inert gas over the surface of the meat, thereby enhancing the colour retention. Again a temporary increase in the CO2
content of the atmosphere surrounding the equipment will occur, but this dissipates rapidly. Solid or liquid nitrogen or CO2
is sometimes used to par-freeze meats prior to slicing. This involves passing the pieces of meat to be sliced through a tunnel in which they are sprayed with the liquefied gas to reduce their temperature to about minus 8°C. In such instances, extractor fans are located near the ends of the tunnel in order to expel surplus gas to atmosphere, and no adverse effects have been reported.
b) Storage under gas
The technique consists of putting a gas – which can be either nitrogen (quality R) or a nitrogen/CO2
mixture – into a tank under very slight overpressure (0.1 to 0.2 bar). Nitrogen is delivered in a compressed state in steel containers. The carbon dioxide is in a liquefied form under pressure.
empaquetado por modificación de la atmósfera
Gas flushing is a process in which products are stored in an artificially produced atmosphere, normally within a plastic container such as a hermetically sealed tray or pouch. The process is also referred to as MAP or Modified... read full description