In processed meats such as ham, salami and chorizo (eg. cold cuts and luncheon meats) there is a tendency for the meat to become discoloured over time if it is stored in air. When raw meats are cured they often assume a red colour as the myoglobin protein in the meat, which is a purple colour, reacts with the nitrogen-containing salts that are usually used during the curing process. This reaction results in a red pigment called nitrosylmyoglobin. If this is subsequently heated, it becomes a pink colour.

These red and pink pigments in processed meats can be affected by oxygen in the air and by light, which cause them to turn a browny grey colour. If the products are packaged in an opaque material, this slows down the discoloration by light. If the product is additionally in a modified atmosphere with little oxygen and elevated carbon dioxide and nitrogen, this will further increase the shelf life.

In addition, processed meat can be spoiled by microbes. These microbes are typically different from those found in raw meat because they are usually introduced during the processing stages, such as drying or marinating. The gas composition for modifed atmosphere packaging also takes into account this particular profile of likely microbial deterioration, and dictates the proportions needed of carbon dioxide and nitrogen.

Typically, modified atmosphere packaging (MAP) increases the shelf life of processed meats from between two and four days to two to five weeks.