Modified Atmosphere Packaging of Cooked Cured and Processed Meat Products

Extending the shelf-life of raw red meat products

Processed meats such as ham, salami and chorizo (eg. cold cuts and luncheon meats) have a tendency 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.

Main spoilage reasons for meat products include microbial growth, color changes and oxidative rancidity. For cooked, uncured meat products, the heating process will kill vegetative bacterial cells, inactivate degradative enzymes, and fix the color. Problems of the similar products primarily come from post-process contamination and/or poor hygiene and handling practices.

Some uncooked, uncured, meat products, such as beef burgers and British sausages, contains sulphur dioxide (often added in the form of sodium metabisulfite). This additive (use of which is restricted to products having a minimum of 6% cereal content) is an effective preservative against a wide range of spoilage mechanisms.

Cured meat products, whether cooked or not, owe their characteristic pink colour to the use of nitrite which interacts with the myoglobin in the meat to form nitrosylmyoglobin. Although this pigment is fairly stable it is prone to oxidative bleaching, especially when exposed to light. Cured meat products should therefore be packaged with the exclusion of oxygen. The addition of nitrite and salt will inhibit most food poisoning bacteria. This inhibition may, however, be compromised in products formulated with reduced levels of salt, nitrite or other preservatives. Caution must be exercised in assessing the potential effects of any changes in product formulation. Simple cooked meats without any added preservatives may be at risk from growth of Clostridium botulinum under anaerobic MAP and incorrect chilled storage.

Meat products containing appreciable levels of unsaturated fat are liable to be spoiled by oxidative rancidity, but MAP with the elimination of oxygen will inhibit this.

General Information for Modified Atmosphere Packaging of Cooked, Cured and Processed Meat Products