Modified atmosphere

Modified atmosphere is the practice of modifying the composition of the internal atmosphere of a package (commonly food packages, drugs, etc.) in order to improve the shelf life.

The modification process often tries to lower the amount of oxygen (O₂), moving it from 20.9% to 0%, in order to slow down the growth of aerobic organisms and prevent oxidation reactions. The removed oxygen can be replaced with nitrogen (N₂), commonly acknowledged as an inert gas, or carbon dioxide (CO₂), which can lower the pH or inhibit the growth of bacteria. Carbon monoxide can be used for preserving the red color of meat.

Re-balancing of gases inside the packaging can be achieved using active techniques such as gas flushing and compensated vacuum or passively by designing “breathable” films known as equilibrium modified atmosphere packaging (EMAP). Packets containing scavengers may be used.

Controlled Atmosphere Storage (CAS) was used from the 1930s when ships transporting fruits had high levels of CO₂ in their holding rooms, thus increasing the shelf-life of the product. In the 1970s MA packages reached the stores when bacon and fish were sold in retail packs in Mexico. Since then development has been continuous and interest in MAP has grown due to consumer demand. This has led to advances, for example in the design and manufacturing of Bacon films. New techniques have been designed, such as the use of anti-fogging layer to improve product visibility. From MAP a new packaging technique, EMAP, has been developed.

The three major commodity types are fruits and vegetables, meat and meat products, and seafood. Many products such as red meat, seafood, minimally processed fruits and vegetables, pasta, cheese, bakery goods, poultry, cooked and cured meats, ready meals and dried foods are packaged under MA. It has been estimated that 25-40% of all fresh produce harvested will not reach the consumers table, due to spoilage and mishandling that occurs during distribution.

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