MAP gases – The basics

Oxygen should not be used in concentrations over 21% unless the packaging machine is compatible *

MAP describes the gases, gas mixtures and services that bring the benefits of Modified Atmosphere Packaging to food manufacturers and suppliers. Food Grade gases from Air Products are a range of high purity gases delivered either as a liquid in stainless steel micro bulk or bulk containers or as a gas in high pressure cylinders all dedicated for use only in the food industry.

Selecting the correct mixture of gases for the Modified Atmosphere is not always simply a matter of choosing a combination that is proven to provide the longest shelf-life. MAP of red meat demonstrates the balancing act that retailers are sometimes obliged to carry out in order to squeeze the best results from this technology. Once it is accepted that it can, in certain cases, make economic sense to sacrifice some shelf-life to ensure enhanced visual appearance it is then necessary to establish which mixtures produce the best results for each different product. Fortunately, the research and trials for most food products have already been carried out and the best balance established. Research in this prime area, however, is being carried out on an almost continuous basis in an effort to produce increased benefits. The balance of gases required for different types of fish, for example, is virtually a study in itself although the chemical and bio-chemical mechanisms at work for all the main food categories, including fish are now well understood. In all cases where presentation is enhanced by the presence of a carefully balanced mixture of gases the retailer benefits because customers find the product so visually attractive.

  The effects of each gas on food products are as follows:

  Carbon dioxide (C02)

Carbon dioxide inhibits the growth of most aerobic bacteria and moulds. Generally speaking, the higher the level of C02, the longer the achievable shelf-life. However, C02 is readily absorbed by fats and water - therefore, most foods will absorb C02. Excess levels of C02 in MAP can cause flavour tainting, drip loss and pack collapse. It is important, therefore, that a balance is struck between the commercially desirable shelf-life of a product and the degree to which any negative effects can be tolerated. When CO is required to control bacterial and mould growth, a minimum of20% is recommended.

  Nitrogen (N2)

Nitrogen is an inert gas and is used to exclude air and, in particular, oxygen. It is also used as a balance gas (filler gas) to make up the difference in a gas mixture, to prevent the collapse of packs containing high-moisture and fat- containing foods, caused by the tendency of these foods to absorb carbon dioxide from the atmosphere. For modified atmosphere packaging of dried snack products 100% nitrogen is used to prevent oxidative rancidity.

  Oxygen (O2)

Oxygen causes oxidative deterioration of foods and is required for the growth of aerobic micro-organisms. Generally, oxygen should be excluded but there are often good reasons for it to be present in controlled quantities including:

•  Maintain fresh, natural colour (in red meats for example)
•  To maintain respiration (in fruit and vegetables)
•  To inhibit bit the growth of anaerobic organisms (in some types of fish and in vegetables)

  Novel gases

Argon Carbon, monoxide , Ozone

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