In the UK MAP mainly involves the use of three gases - carbon dioxide, nitrogen and oxygen - although other gases are in use around the world. Products are generally packed in combinations of the gas trio, with the mix dependent on the physical and chemical properties of the food.

Perhaps nowhere can rival the UK in its extended use of MAP. Food producers here have taken to the technique in droves, with the logistical, demographic and cultural structure of the British Isles making them so ideal for MAP use that few companies with a fresh or chilled food operation can carry on without it.

These are some of MAP’s benefits:

SHELF LIFE EXTENSION: Depending on the product, the time an item can remain on display in a supermarket or shop can usefully be extended by between 50 and 500 per cent using MAP techniques. This means waste is minimised and ordering and restocking are more flexible.

MINIMISATION OF WASTE: If there is a greater chance of a product being sold, as there is with MAP because food can be displayed longer, there is obviously less chance of having to throw it away at the end of its life - which will come no matter how effective MAP has been in prolonging it.

QUALITY: There are obvious advantages for both retailer and consumer in having food, which deteriorates at a slower rate as it makes its journey from place of production to the domestic kitchen, fridge or freezer.

PRESENTATION: Because MAP products can’t merely be wrapped in film - they have to be encased, usually in a tray - retailers have every opportunity to package more attractively. So visual display becomes another key component in MAP's story of effectiveness.

REDUCING THE NEED FOR ARTIFICIAL PRESERVATIVES: In a world where we are all intent on becoming 'greener' in our outlook, with a determination to do all we can to protect the environment, there are advantages to getting rid of as many additives as possible. The goal is food, which is NATURALLY fresh and in some cases using MAP means that no artificial preservatives are required at all to achieve a reasonable shelf life.

All these benefits have wide-ranging applications but they are particularly pertinent to those engaged in production of ready meals and cook-chill products. MAP can significantly extend the shelf life of a whole range of such products. Apart from delaying microbial spoilage, the use of a carbon dioxide/nitrogen gas mix (in a 2:1 ratio) has also been found to delay the development of oxidative warmed-over flavour.

Cook-chill means food is hygienically prepared, pasteurised and rapidly chilled to between zero and three degrees centigrade. Food is then stored at similar temperatures before being reheated to 70 degrees C for a period prior to consumption.

Under Department of Health guidelines issued in 1989 for cook-chill for the catering industry, the maximum recommended shelf life for products is five days. But this period can be extended if the food is packed under modified atmosphere conditions or cooked under vacuum for the retail market. Tests have shown that for ready meals and cook chill products with a shelf life of two to five days, modified atmosphere packaging can increase this to between five and 10 days - a hugely worthwhile life extension.

Among ready prepared foods which can benefit are those containing fish, game, meat, pasta, poultry and vegetables as well as casseroles, soups and sauces.

The Advisory Committee for Microbiological Safety of Foods has looked into this whole topic and has concluded that chilled foods with a shelf life shorter than 10 days should, if kept at chilled temperatures, present a minimal risk of the growth of toxin production by clostridium botulinum. The principal method of spoilage of ready meals and other cook-chill products is microbial growth, caused primarily by post cooking contamination, poor temperature control or a combination of the two. Strict control over temperature, handling and hygiene should obviously be maintained throughout so that MAP can play its full part.

If all the guidelines are adhered to ready meal producers, packers and retailers anxious to join the trend towards convenience, both for packing and display, will find rich rewards coming from any venture into MAP. Many have tried and few have failed. Indeed, the majority of the system’s devotees find it hard to contemplate what life was like without it.

Suppliers of MAP gases