Gases
The atmosphere in an MA package consists of N2, O2, CO2. It is the altered ratio of these gases that makes a difference in the prolongation of shelf life. By reducing the O2-level and increasing the CO2-level, ripening of fruits and vegetables can be delayed, respiration and ethylene production rates can be reduced, softening can be retarded and various compositional changes associated with ripening can be slowed down.
Oxygen is essential when packaging fresh fruits and vegetables as they continue to respire after harvesting. The absence of O2 can lead to Anaerobic respiration In the package which accelerates senescence and spoilage. Too high levels of O2 do not retard respiration significantly and it is around 12% of O2 where the respiration rate starts to decrease. So oxygen is used in low levels (3-5%) for positive effect. When packaging meat and fish, the high CO2-levels are effective bacterial and fungal growth inhibitors. In the case of vegetables and fruits, CO2 is not a major factor since CO2-levels above 10% are needed to suppress fungal growth significantly. Unfortunately higher levels than 10% of CO2 are working phytotoxic for fresh produce. Nitrogen is used as a filler gas since it neither encourages or discourages bacterial growth.
In recent years, there has been debate regarding the use of carbon monoxide (CO) in the packaging of red meat. While no risk was found in the use of low levels of CO, the fact that CO maintains the color of the meat and can, in that way, hide visual evidence of spoilage was raised. The European Food Information Council (EFIC) released a report in 2001 reviewing the data.
Read more about this topic: Modified Atmosphere
Famous quotes containing the word gases:
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—Ralph Waldo Emerson (1803–1882)