Modified Atmosphere Packaging

MAP is food packaging in which the earth’s normal breathable atmosphere has been modified in some way. Usually combined with lowered temperatures, it is a highly effective method for extending the shelf-life of food.

Shelf-life is prolonged in some applications by creating a simple vacuum in the package (vacuum packaging) and in these cases there is almost a complete absence of gas. In others, special permeable films allow naturally respiring produce to form its own atmosphere without the addition of external gases.

Once a fruit, vegetable or animal product is harvested or slaughtered it remains a suitable environment for bacteria which continue to function using the available carbohydrate, protein, fat and nutrients. These continuing processes lead to degradation including undesirable colour changes, loss of flavour and poor texture. The action of enzymes also causes deterioration of foods. In Europe, MAP mainly involves the use of three gases - carbon dioxide, nitrogen and oxygen, although other gases are used where regionally acceptable. Products are packed in a single gas or a combination of these three gases depending on the physical and chemical properties of the food.

History of MAP

The use of gases in the preservation of food products is by no means a new process. Much of the original work was carried out in the early 1930s with the shipment of beef and lamb carcasses from Australia and New Zealand to the UK under carbon dioxide storage. During the 1940s and 1950s, sealed controlled atmosphere storage warehouses were constructed to prolong the effective shelf-life of fresh apples under refrigeration. Hence the commercial applications of gas preservation were largely confined to the controlled atmosphere storage and transport of bulk commodities such as meat and fruit.

 

Now you see MAP used to package anything from fresh salads and individual meat portions, to sandwiches and snacks. Today it is a sophisticated technique with ever-increasing benefits to both supplier and customer.

Adding Value on Food

Food, glorious food - in all its natural, eye-catching colour - is what the customer expects from the food industry. And week in, week out, Modified Atmosphere Packaging techniques help the retailer to deliver. Extended shelf-life, greater choice and a reduction in food-related health hazards are some of the valuable benefits of MAP but are not so apparent to the shopper as the presentation of the food itself. This is where MAP adds even more value for the retailer enabling food to look better for longer.

Tray Lidding

A traysealer uses ready-made trays that are sealed in much the same way as a thermoformer. The top web of packaging material (lid film) covers the filled pockets/trays. The air is evacuated from the sealing die and protective gas is added. This can be done using vacuum pump or through a process called gas flushing. Then the pack is sealed by the application of heat and pressure. Tray lidding machines are available from tabletop (manual) for the small producer, to fully automatic inline versions for larger processors.