Modified Atmosphere Packaging
Flesch-Kincaid Grade Level: 10.1
What is Modified Atmosphere Packaging?
Modified Atmosphere Packaging (MAP) is a packaging technique used to extend the shelf life of
fresh food. It works by surrounding the food with gases that stop, or at least slow down the growth
of bacteria, yeasts and moulds that spoil food. Without these microbes, food can be kept for longer
periods of time and will take longer to spoil, or may age at a slower rate.
The types of food stored this way include vegetables, salad greens, pasta, meat, fruit, cheese,
seafood and bakery products such as sandwiches. The term MAP is also sometimes used for
vacuum-packaging (often used for cured meats, hard cheeses and seafood).
Foods packaged this way are generally safe because the growth of pathogens is inhibited. However
MAP does not completely eliminate pathogens, and without spoilage microbes, there are fewer
obvious signs of decay (eg, it smells ‘off’ or is discoloured) to indicate the food may be unsafe to eat.
This page outlines how MAP works, what regulations govern MAP and how to choose and store
MAP foods to reduce build up of pathogens.
Has anyone become ill from MAP foods?
No, there are no reports of illness from MAP foods in New Zealand. Overseas, two outbreaks have
been linked to MAP vegetable products:C. botulinum in coleslaw in the U.S.A (Solomon et al, 1990)
andSalmonella in salad vegetables in the U.K. (Public Health Laboratory System, 2001) Luckily
pathogenic C. botulinum has not been a problem in our country to date.
How does MAP work?
Most spoilage micro-organisms are aerobic so they need oxygen (O2) to grow. In MAP foods, oxygen
is commonly replaced with a mixture of ozone (O3), carbon dioxide (CO2) or nitrogen (N2). Nitrogen
is used as a filler gas to displace other gases and to prevent the package from collapsing.
The atmosphere in the package can be created actively (at the time the package is sealed) or
passively develop over time. Selectively permeable films on passive MAP foods allows some gases
to escape and traps others inside. Active and passive methods can be combined.
Keep MAP foods refrigerated
Yes. Most MAP foods need to be kept in the fridge because:

cool temperatures keep pathogen growth in check. Pathogens such
as Clostridium, Listeria and Aeromonas can still grow in packages with little or no oxygen,
and fridge temperatures stop them multiplying to dangerous levels
 cool temperatures make the gas mixtures more effective at controlling bacteria.
Are there regulations for using MAP?
Yes. Under the Australia New Zealand Food Standards Code, packaging must not cause food to be
unsafe or tainted. While there are no regulations about which foods can be stored in MAP, it is up to
the manufacturer to protect the customer from illness and providing storage instructions and date
markings on how to store and handle the product safely.
A date mark is required on all MAP foods
All MAP food must be labelled with a ‘best-before’ or a ‘use-by’ date. The best before date is
recommended for products such as meats that are cooked before consuming and is a guide to when
the product will begin to deteriorate. A use-by date is used when a product can become unsafe
which means once a use by date has expired, you should not consume the food even if the package
is intact. It is illegal to sell food past its use-by date.
Follow storage instructions to prevent pathogen build-up
Most MAP food still requires strict temperature controls, so storage instructions are essential.
Cooler temperatures help control any growth of micro-organisms and also improve the effect of the
MAP gases on bacteria. If the food is kept under the recommended conditions, it is likely to be safe
to eat until the use-by date is reached.
Once the package is opened, the label should instruct you on how to store the food, and how long
the food will remain safe under these conditions (eg, “refrigerate upon opening, consume within
two days”).
Can meat be stored in MAP?
Yes. Different ratios of gas may change the appearance of meat and make it appear less attractive to
the buyer. Producers must balance the need to suppress spoilage microbes with the desirability of
the product. Fresh meat appears red because oxygen interacts with the natural pigments
(myoglobin). But under low levels of oxygen or a high concentration of CO2, meat turns a purple-red
colour which, though still safe to eat, is not as desirable. The bright red colour returns quickly on
exposure to air when the package is opened.
Carbon monoxide (CO) interacts with myoglobin to forms a stable, bright red colour but this
reaction prevents meat from browning naturally with age so it is difficult to tell how fresh the meat
is (Brooks, 2008). For this reason, the use of CO for meats stored under MAP is banned in the
European Union, but is still permitted in the United States and is used in small concentrations
(<1%) for some New Zealand meats.
Producers must formulate a gas mixture and packaging system that keeps the product appealing,
and maintains the product safety.
Treat MAP foods as if it were fresh
Clean

work in a clean kitchen with clean utensils, bowls and boards
prepare MAP foods with the same safety precautions as perishable food. This means

washing fresh MAP salad greens, etc
use before the expiry date, and use within the specified storage time once opened

Cook

if the MAP food requires cooking, make sure it is cooked until steaming hot
Cover


keep raw foods separate from fresh foods
cover food to protect it from contamination
Chill
keep MAP foods refrigerated, or store as instructed on the package
 keep cold foods cold before cooking or eating
 quickly chill hot foods that are to be kept longer
 if you have frozen MAP food intact (eg, pasta), once thawed, use it straight away
References
Solomon H.M., Kautter D.A., Lilly T. & Rhodehamel E.J. (1990) Outgrowth

of Clostridium botulinum in shredded cabbage at room temperature under modified
atmosphere. Journal of Food Protection 53 (10):831-833.
[PHLS] Public Health Laboratory System. (2001) June 28. SalmonellaNewport infection in England
associated with the consumption of ready to eat salad. Eurosurveillance Weekly 2001(26).
Brooks, J.C., Alvarado, M., Stephens, T.P., Kellermeier, J.D., Tittor, A.W., Miller, M.F., Brashears, M. M.
(2008) Spoilage and Safety Characteristics of Ground Beef Packaged in Traditional and Modified
Atmosphere Packages. Journal of Food Protection, 71(2): 293301(9).http://www.ingentaconnect.com/content/iafp/jfp/2008/00000071/00000002/art00007;j
sessionid=1k5v82cf6mjcc.henriet
http://www.foodsmart.govt.nz/food-safety/high-risk-foods/modified-atmosphere-foods/