MAP gases – the basics

Freshline® Food Grade gases from Air Products are a range of high purity gases delivered either as a liquid in stainless steel microbulk or bulk containers or as a gas in high pressure cylinders all dedicated for use only in the food industry.

Before choosing a gas mixture, many factors should be considered. A product trial is the most effective method of identifying the optimum gas mixture for your process. Contact one of our Freshline® specialists for more information.

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

Carbon dioxide (CO₂)

Carbon dioxide inhibits the growth of most aerobic bacteria and moulds. Generally speaking, the higher the level of CO₂, the longer the achievable shelf-life. However, CO₂ is readily absorbed by fats and water - therefore, most foods will absorb CO₂. Excess levels of CO₂ 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 CO₂ is required to control bacterial and mould growth, a minimum of 20% 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 the growth of anaerobic organisms
  (in some types of fish and in vegetables)