A packaging method that replaces the air around a food with a controlled gas mix to extend shelf life.
A packaging method that replaces the air around a food with a controlled gas mix to extend shelf life. Modified atmosphere packaging, or MAP, is a technique where the ordinary air surrounding a food inside its pack is replaced with a controlled mixture of gases, usually some combination of carbon dioxide, nitrogen and sometimes oxygen. By changing the atmosphere, MAP slows the growth of spoilage organisms and chemical changes such as oxidation, extending the shelf life of products like fresh meat, fish, salads and bakery goods. While MAP controls spoilage, it does not make a food safe on its own and can change which organisms are of concern. Reducing oxygen can suppress some aerobic spoilage bacteria while creating conditions that favour anaerobic pathogens, so the safety of MAP foods still depends on refrigeration, the intrinsic properties of the food such as pH and water activity, and appropriate date marking. A manufacturer using MAP needs to select a gas mix suited to the product, validate that it delivers the intended shelf life, and control refrigeration through the supply chain, because low oxygen does not remove the need for temperature control. The extended shelf life claimed on the label must be supported by validation and the product kept at the labelled storage temperature. For a retail or food service business receiving MAP products, the key points are to check the pack is intact and gas-flushed, store it at the correct temperature, and observe the use-by date, discarding any pack that has been opened or damaged since opening breaks the modified atmosphere. Extra care is warranted for chilled, long shelf life MAP foods where anaerobic pathogens are a consideration. A processor packing fresh chicken portions flushes each tray with a carbon dioxide and nitrogen mix to slow spoilage, validates a shelf life at 4 degrees Celsius or below, marks the trays with a use-by date and storage instruction, and a supermarket then keeps the trays refrigerated and pulls any pack whose seal has failed.
Frequently asked questions
What gases are used in modified atmosphere packaging?
MAP typically uses a controlled mix of carbon dioxide, nitrogen and sometimes oxygen, chosen to suit the particular food and slow spoilage.
Does MAP make food safe without refrigeration?
No. MAP slows spoilage but does not remove the need for temperature control, and many MAP foods still require refrigeration and a use-by date.
Can MAP create new safety risks?
Reducing oxygen can suppress some spoilage bacteria while favouring anaerobic pathogens, so safety still relies on refrigeration and the food's pH and water activity.
How is the shelf life of a MAP product decided?
It must be validated for the specific product and gas mix, and the labelled shelf life is only valid if the food is kept at the stated storage temperature.
What should a business do if a MAP pack is damaged?
A damaged or opened pack has lost its modified atmosphere, so it should be treated as an ordinary chilled food and used quickly or discarded if in doubt.
