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Modified Atmosphere Packaging (M.A.P) The method of controlling post harvest changes in fruit and vegetables during storage in a gas-tight storage room which is regulated by means of monitors and whose environment (temperature, gas content and humidity) is closely controlled is known as controlled atmosphere packaging or storage (C.A.P). This method has been available for some time. A related method, known as modified atmosphere packaging (M.A.P), is also used in extending shelf life of certain food products. This method involves packaging a food into a container and then replacing the air present in the container with a mixture of pure gases specifically formulated to inhibit or retard chemical changes in the food, affect the rate of ripening or the color of fresh product and reduce or stop the growth of micro-organisms. M.A.P has been successfully used in the presentation of fresh meat products in retail outlets where color is a major factor influencing the consumer's decision to buy a particular product. In this case, various gas mixtures can be used to retain the red color and 'sheen' of meat to improve its appearance. Poultry and fish products can also have their shelf life extended, and in some cases, their appearance enhanced by use of M.A.P The below table shows typical gas mixtures for some meat and fish products
Fresh vegetable products can have an extended shelf-life in the retail outlet by being packaged in a container within which the local atmosphere is designed to prolong the normal metabolic processes of the live plant material. In all cases oxygen is present in the gas mixture. However, it is also possible to use the method to exclude oxygen from the package containing cooked, chilled foods by replacing it with other gases. Carbon dioxide has been shown to be a powerful inhibitor of the growth of micro-organisms. Also micro-organisms do not use nitrogen and other inert gases in their metabolic processes. Thus, the mixtures of carbon dioxide and nitrogen have been used to replace air within containers. In addition, carbon dioxide can be added to enrich the air already present in the container. The former method, which requires prior vacuumising of packaged food, removes all oxygen and thus inhibits oxidative changes whereas the latter does not. History
of cook-chill
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