Oxygen

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Oxygen

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.

Modified atmosphere is a common technical definition that describes the practice of modifying the composition of the internal atmosphere of a package (commonly food packages, but this technique is also used for drugs) in order to improve the shelf life.

The modification process often tries to lower the amount of oxygen (O2), moving it from 20% to 0%, In order to slow down the growth of aerobic life forms and the speed of oxidation reactions. The removed oxygen can be replaced with nitrogen (N2), commonly acknowledged as an inert gas, or carbon dioxide (CO2), which can lower the pH or inhibit the growth of bacteria.