Carbon monoxide and meat
Modified atmosphere packaging and meat
A modified atmosphere which maintains optimal quality and safety is the ultimate goal in MAPpackaging. Consumers often judge meat quality by colour and appearance. The colour of meat is influenced primarily by the condition of a natural pigment known as myoglobin. Exposure to air is a major factor influencing the colour of the pigment. Immediately after slaughter, red meat appears purple, but will turn red upon exposure to oxygen. Prolonged exposure results in a brown or grey colour.
High oxygen MAP systems are most widely used for meat. These systems allow oxygen to attach to myoglobin, forming oxymyoglobin, which gives meat the bright red colour associated with freshness. However, the presence of oxygen allows for potential growth of spoilage and harmful aerobic (oxygen-requiring) bacteria and for lipid oxidation. These cause foul smells, slime and premature browning. Premature browning presents a safety concern as consumers often use colour as an indicator of ‘doneness’ and the meat may turn brown before safe internal temperatures are obtained.
Low oxygen MAP systems usually have high levels of carbon dioxide. This gas is able to effectively prevent bacterial growth (aerobic microorganisms). A disadvantage is that low levels of oxygen cause dominance in myoglobin, which gives meat an unappealing purple colour.
Modified atmosphere packaging (MAP) is a packaging technology that has been used since the ‘70’s to extend the shelf life of fresh produce and other perishables. MAP involves removing gases from or changing gas concentrations of the atmosphere inside the food package. This action serves to reduce natural spoilage processes, and extends meat shelf life. The desired atmosphere is maintained within the package by the use of packaging materials that significantly affect the transfer of gases into and out of the package.
Carbon monoxide in MAP
Carbon monoxide (CO) is a colourless, odourless gas that is used in MAP for meats in theUnited States. When inhaled, carbon monoxide can be fatal. However, ingestion is not harmful to health. The FDA recognizes CO as a GRAS (generally recognized as safe) compound forMAP use at maximum concentrations of 0.4%. CO is a relatively recent introduction to MAP; gases traditionally adjusted in MAP are oxygen, nitrogen and carbon dioxide(CO2).
Carbon monoxide extends shelf life by inhibiting various spoilage bacteria and maintaining a bright red colour in meat for longer periods of time. The bright red colour is caused by the binding of carbon monoxide to myoglobin, forming carboxymyoglobin, which is more stable compared to other forms of myoglobin.
Concerns have been raised over the possibility that the colour-preserving property of carbon monoxide is being used to prevent the potential change of colour of spoiled meat and thus deceive consumers. However, there are other indicators of spoilage, such as foul smells and slime, which are also readily detectable by the consumer. Additionally, the FDA requires the labelling of CO-treated meats with a use-by date, which clearly states the amount of time the product will remain safe for consumption.
In the United States, media attention has been given to the proposal of a complete ban on the use of carbon monoxide in foods by various consumer groups and companies. These parties cited carbon monoxide bans in food in other countries, such as Europe and Canada, as support for their argument.
In 2001, the European Commission carried out a review of the safety of carbon monoxide in foods and determined the application to be safe. The use of carbon monoxide in food packaging had already been established in Norway for 20 years without incident. Despite this, it was determined that most consumers were not ready to accept the technology and the use of carbon monoxide was prohibited. A similar review was conducted by the U.S. Food and Drug Administration (FDA) in the early ‘90’s, and repeated reviews followed at the urging of concerned parties. The conclusion of every review was that carbon monoxide in food packaging does not produce a product that is harmful to human health.
There is a misconception popularized by opposing parties that carbon monoxide use is illegal in the United States, due to a prohibition in Section 173.350 under the Food and Drugs section (Title 21) of the Code of Federal Regulations. This section actually defines the allowable quality and the maximum concentration (4.5%) of carbon monoxide for safe use in food processing and packaging.
In Canada, carbon monoxide is now a permitted as a processing aid under certain conditions. Health Canada issued a letter of "no objection" in 2010 for the use of carbon monoxide at 0.4% with meat in a specific MAP system.
Meat is subject to natural spoilage processes no matter what type of packaging is used. It is, therefore, important to keep meat at refrigeration (4°C or less) temperatures throughout storage, sales and distribution. Consumers should take care to use the meat by the date indicated on the package, and practice safe food handling techniques.
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