Generally speaking, carbon dioxide (CO2) has a strong inhibiting effect on the growth of bacteria in meat and poultry. The aerobic genus Pseudomonas is the largest problem for fresh meat.
Discolouration caused by oxidation of the red pigment in meat is a particular challenge. In order to retain the red colour, the atmosphere for fresh meat should contain high levels of oxygen (60 - 80%). This maintains high oxygen levels in the meat's myoglobin. Highly pigmented meats, such as beef, require higher oxygen concentrations than meats with low pigmentation levels such as pork.
With the right MAPAX mixtures, the practical shelf life of consumer-packaged meats can be extended from 2-4 days to 5-8 days at +3.33oC (37.99oF). If master packs are used in distribution, high CO2 levels can further increase shelf life.
Protective Atmospheres - MAP Mixtures - Meats
| Product | Red Meat | Poultry |
| MAPAX gas mixture | 20% CO2 and 80% N2 |
50-80% CO2 and 20-50% N2 |
| Gas volume on weight basis | 100-200ml per 100g meat | 100-200ml per 100g meat |
| Typical shelf life | 2-4 days in air 5-8 days with MAP |
7 days in air 16-21 days with MAP |
| Typical material* | OPET/PVdC/PE-PVC/PE | OPET/PVdC/PE-PVC/PE |
| Typical machine | Deep-draw machine | Deep-draw machine |
| Storage temp. | +1.66oC to +3.33oC |
+1.66oC to +3.33oC |
| *PVC is being replaced by APET or PS/EVOH PVdC is being replaced by WVOH or OPA |
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Protective Atmospheres - MAP Mixtures - Prepared Meats
| Product | Sausages | Sliced cooked meat products |
| MAPAX gas mixture | 20% CO2 and 80% N2 |
20% CO2 and 80% N2 |
| Gas volume on weight basis | 50-100ml per 100g product | 50-100ml per 100g product |
| Typical shelf life | 2-4 days in air 4-5 weeks with MAP |
2-4 days in air 4-5 weeks with MAP |
| Typical material* | OPET/PVdC/PE-PVC/PE PA/PE | OPET/PVdC/PE-PVC/PE |
| Typical machine | Deep-draw machine |
Deep-draw machine |
| Storage temp. | +4.44oC to +7.22oC |
+4.44oC to +7.22oC |
| *PVC is being replaced by APET or PS/EVOH PVdC is being replaced by WVOH or OPA |
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Poultry
Poultry is very susceptible to bacterial spoilage, evaporation loss, off-odour, discolouration and biochemical deterioration. Sterile poultry tissue quickly becomes contaminated during the evisceration process.
The practical shelf life of gas-packed poultry is somewhere between 16 and 21 days. The head space volume should be nearly as large as the product volume. In contrast to red meats, poultry does not undergo irreversible discoloration of the meat’s surface in the presence of oxygen.
The spoilage of raw poultry is mainly caused by microbial growth, fuelled by the Pseudomonas and Achromobacter genera in particular. These aerobic bacteria are effectively inhibited by modified atmospheres containing CO2. Levels of CO2 in excess of 20% are required to significantly extend the shelf life of poultry.
To avoid problems associated with collapsed packaging and excessive dripping with raw poultry, the gas/product ratio should be increased if higher levels of CO2 are used. Where package collapse is not an issue (e.g. bulk or master bags), 100% CO2 is recommended. In both retail and bulk modified atmosphere packs, nitrogen is used as an inert filler gas.