Modified Atmosphere Packaging (MAP) and measuring permeability Modified atmosphere packaging (MAP) is "the packaging of perishable produce in an atmosphere which has been modified, rather than air." The gaseous composition of MAP foods constantly changes due to chemical reactions and microbial activity. Gases flow between the inside of the pack and the external environment via the permeability of the package material.

Traditionally measuring the O2 and CO2 of films for developing packaging or quality control was a difficult and long-winded task.  Fortunately, it can now be done simply and quickly with the new Versaperm MK VI permeability equipment.  The basic instrument measures water vapour permeability (probably the single most important measurement for extended shelf life) and options are available to measure Oxygen (O2), Carbon Dioxide (CO2) and most other important gases. Our instrumental technique for measuring the permeability of modified atmosphere packaging packaging can measure flat samples, entire packs and whole packs with the produce in situ. The equipment has an highly automated computerised control which can cope with several MAP samples at a time giving water vapour results that can be accurate to better than one part per million.  Sensitivities are in the range 0.05 - 3200 g/m2/day. If produce is packed with films where the permeability is too low, Oxygen levels will be below the optimal, and CO2 levels too high. This allows taints to develop and the pack may not smell fresh when opened.  Where permeability is so low that normal respiration cannot be sustained, fresh produce will start to ferment generating “off’ flavours and odours that range from cut grass to alcoholic.  This can greatly reduce shelf life and can even become a food safety hazard. Click here for a MAP Press release Click here for Wikipedia's Modified Atmosphere Packaging (MAP) page A MAP sample testing service is also available from the company - often with a 24 hour turn around