Modified Atmosphere Packaging Up and Coming

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In the fresh produce segment of food retail MAP's market share has risen significantly over the past few years. The benefits of this inert gas packaging obviously include not only longer shelf life for the packaged products but also suitability for merchandise that cannot be placed under vacuum.

Thanks to the MAP process (Modified Atmosphere Packaging) it has become possible to optimise the atmosphere inside packaging units in such a way that the quality of the product is retained for an extended period of time. As the term implies, this modified atmosphere packaging involves film packaging treated with a modified atmosphere. The gases used are usually carbon dioxide, nitrogen and at times oxygen. These shielding gases are not detrimental to health, obtained from the air and have to fulfil high purity requirements.

MAP is manufactured using deep-drawing machines or tray sealers. While deep-drawing machines process films from reels filled in-line, the tray sealers seal pre-fabricated containers. Polypropylene trays offers excellent protection from water vapour. For a fully automatic machineability they must have an even and broad sealing rim, be easy to de-stack and feature excellent bottom and permanent seal flatness.

For this application the oxygen included in the packaging is removed by vacuum or purged – depending on the machine – and then the packaging is re-gassed. For MAP barrier films and/or composite films are used. Depending on the required properties rigid or soft films are used. To ensure the gas does not escape the packaging, barrier films with a barrier effect tuned to the specified shelf life are needed. In addition to high transparency outstanding anti-fog properties are required here to keep water drops from forming inside the film to prevent fogging. The modified atmosphere inside the packaging creates a gas-filled space that counteracts atmospheric pressure to such an extent that even pressure-sensitive products can be packaged with long shelf lives without risk of damage – and without the addition of preservatives.

The Atmosphere Shares and their Effect

Nitrogen serves as a supporting gas, filling the voids and ensuring pressure compensation between inside and outside. This means the merchandise rests loosely in the packaging and is protected against deformation, slices do not stick to each other and release of liquids is minimised. The carbon dioxide (CO2) is dissolved in water and forms carbonic acid (H2CO3). During the packaging process a slightly acidic, preserving film forms on the surface of aqueous products. This acid atmosphere inhibits the growth of most bacteria and mould fungi. The carbon dioxide evaporates as soon as the packaging is opened or the product is heated. Furthermore, a high oxygen concentration prevents meat surfaces from turning brown by de-oxidation under vacuum. This means the fresh colour is retained and foodstuffs – like fruit and vegetable – can “breathe”. In addition this selective supply of oxygen makes for a substantially longer shelf life of many products because it prevents fermentation and excessive anaerobic bacteria counts.

Makes sense for many applications

Therefore MAP makes for a longer shelf life of the packaged products, reduces rejects, makes products look more appetising and renders the use of preservatives superfluous. This means it can increase productivity – and open up new markets. Modified Atmosphere Packaging makes sense for packaging many different products: rolls and pastry products for crisping up again, pasteurized foods such as pasta and instant meals, fresh meat, cold cuts or sliced cheese, sausages, fresh cheese and cut fruit and – needless to say – fresh meat, which keeps its appetising colour, a principal criteria for consumers when purchasing meat. They expect a fresh red to light red colour, brownish grey or darker shades are often associated with “old” or even “perished”.


The thinner the better

The thinner films and trays are the better. Material savings, compensation of higher raw material prices and resource-saving processes are as centre stage as ever. Furthermore, biodegradable trays and films are the 'talk of the town'. PLA has already been enjoying particular success being water-resistant and processable like a thermoplastic. Even the look of such materials has substantially improved now. Packaging materials from renewable raw materials are also up and coming in this segment.