I know that Modified Atmosphere Packaging creates good conditions for the multiplication of anaerobic bacteria, and that some of them can be pathogenic. What is done to guarantee the safety of Modified Atmosphere Packaged (MAP) products?

Germany

MAP is just one way to ensure the safety of a product. It limits the multiplication of aerobic bacteria and moulds by taking the air away which is necessary for their growth. However, there are still microorganisms (also pathogens) that could grow under these conditions, because they do not need air. The multiplication of these is controlled by a number of measures such as refrigeration, limiting the amount of water needed for multiplication, the addition of preservatives, etc. depending on the nature of the product. Still adequate preparation of food for consumption plays an important role in preventing food borne disease, and thus general hygiene rules and specific instructions (if any) need to be applied.

Technically speaking, Modified Atmosphere Packaging (MAP) relies on altering the composition of gases in contact with the food by replacing air with a single gas or a mixture of gases, a unique atmosphere for that product is created, usually enriched in CO2 and reduced in O2. This favourable atmosphere slows the metabolic activity of the produce to a very low level, and thus MAP enables the storage of highly perishable produce for prolonged periods. This is then combined with low temperature storage of less than 3 °C.

Elevated CO2 and reduced O2 levels slow quality loss in a number of ways. High CO2 and low O2 atmospheres can:

• Block the mode of action and biosynthesis of ethylene, a ubiquitous plant hormone which promotes aging and senescence.
• Reduce rots by directly inhibiting the growth of pathogens and by maintaining the health and integrity of the plant tissue, which reduces its susceptibility to infection, low O2 atmospheres work well to inhibit the growth of strict aerobic spoilage bacteria and high CO2 levels have high fungistatic and bacteriastatic effects.
• Slow yellowing of green tissues by preventing chlorophyll degradation
• Maintain the food and nutritional value and flavour of produce by slowing the loss of food reserves, particularly sugars, inhibiting the loss of labile vitamins such as vitamins C and A, and by slowing the accumulation of undesirable secondary metabolites in the plant's tissues, such as free ammonia.
• Slow cell membrane degradation and loss of cellular compartmentation and function.
• Inhibit discolouration of cut surfaces.

Also see:

• http://www.eufic.org/gb/food/pag/food33/food333.htm
• http://rics.ucdavis.edu/postharvest2/pubs/kader_ma_2000.pdf
• http://www.who.int/health_topics/foodborne_diseases/en/