What
is MAP?
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.
Why use MAP?
In the last 25 years, the change from an industrialised base to a service
economy has seen the emergence of new family structures and work patterns which,
in turn, has led the demand for more convenient food.
The creation of nationwide, European and international supermarket chains,
has led to a highly competitive trading environment, forcing quality up and
operational costs down
For the food industry, one of the important effects of these significant
social, economic and business changes has been to open the door to MAP. Hundreds
of food businesses have stepped through, using MAP to form valuable new trading
relationships with the multiples and other, smaller chains and independents.
Because Modified Atmosphere techniques are ever changing and improving, that
door of opportunity remains open.
Extension of shelf-life
Depending on product, shelf-life can be usefully extended by between 50% and
500% using MAP techniques. This means that waste is minimised and re-stocking
and ordering can become more flexible.
As an example, a store turning over 100% of its shoppers every 10 days will
be able to offer a non-MAP food item with a shelf-life of three days to just 30%
of its customers. But the same food item packaged with a suitable Modified
Atmosphere to give it a 10-day shelf-life will be available for purchase by ALL
the store’s shoppers.
Minimisation of waste
If there is a greater chance that a product will be sold, there is obviously
less chance of it being thrown away. Even with today’s sophisticated
management systems it is still not possible to accurately predict a
supermarket's daily throughput. So having a greater shelf-life available enables
a store to order more efficiently and to reduce wastage.
Quality
There are obvious quality advantages for both retailer and consumer in
having food that deteriorates at a much slower rate on its journey from
production area to store, and then onward to the domestic kitchen, refrigerator
or freezer.
Presentation is another vital quality aspect. Because MAP products cannot just
be wrapped in cling film (they have to be encased, usually in a tray which lends
itself to an element of design on its surface) retailers have taken the
opportunity to package their food stuffs more attractively. The visual appeal of
food is another key quality area and here the industry’s experience with red
meat makes an interesting case study. After slaughter and ageing, red meat
quickly becomes a dullish, brown colour which is unattractive to customers.
Fresh, red colour is maintained longer using a mixture of between 70% and 80%
oxygen, (depending on the meat), and carbon dioxide for the balance. Its
remarkable effect on red meat is undeniable. In the early days it was the
introduction of this technique by Marks & Spencer to its range of red meats
that kick-started the use of MAP in the UK. Today, with red meat coming under
scrutiny by some consumers actively pursuing a healthier lifestyle, the role of
MAP is central to its survival on store butchery shelves.
Reduced need for artificial preservatives
In a world which is becoming increasingly “green” in its outlook, a world
where every consumer is a watchdog for the environment, there are points to be
earned by the retailer who can get rid of as many additives as possible and show
that its food is basically fresh and natural. In some cases, MAP means that
artificial preservatives are no longer required to achieve a reasonable
shelf-life.
Increased distribution possibilities
Because of the extended product shelf-life, increased distribution is one of
those areas in which the introduction of MAP is more than just “another
benefit”. For companies with the right product, the potential to increase the
range of delivery can produce exciting changes and opens the door to a global
market.
MAP
Gases
BOC (www.boc.com.au) has a range of high purity gases delivered either as a
liquid in stainless steel microbulk or bulk containers or as a gas in high
pressure cylinders all dedicated for use only in the food industry.
Before choosing a gas mixture, many factors should be considered. A product
trial is the most effective method of identifying the optimum gas mixture for
your process.
The effects of each gas on food products are as follows:
Carbon
dioxide (CO2)
Carbon dioxide inhibits the growth of most aerobic bacteria and moulds.
Generally speaking, the higher the level of CO2, the longer the
achievable shelf-life. However, CO2 is readily absorbed by fats and
water - therefore, most foods will absorb CO2. Excess levels of CO2
in MAP can cause flavour tainting, drip loss and pack collapse. It is important,
therefore, that a balance is struck between the commercially desirable
shelf-life of a product and the degree to which any negative effects can be
tolerated. When CO2 is required to control bacterial and mould
growth, a minimum of 20% is recommended.
Nitrogen
(N2)
Nitrogen is an inert gas and is used to exclude air and, in particular,
oxygen. It is also used as a balance gas (filler gas) to make up the difference
in a gas mixture, to prevent the collapse of packs containing high-moisture and
fat-containing foods, caused by the tendency of these foods to absorb carbon
dioxide from the atmosphere. For modified atmosphere packaging of dried snack
products 100% nitrogen is used to prevent oxidative rancidity.
Oxygen
(O2)
Oxygen causes oxidative deterioration of foods and is required for the growth
of aerobic micro-organisms.
Generally, oxygen should be excluded but there are often good reasons for it
to be present in controlled quantities including:
- Maintain fresh, natural colour
(in red meats for example)
- To maintain respiration
(in fruit and vegetables)
- To inhibit the growth of anaerobic organisms
(in some types of fish and in vegetables)
