Oxygen
What it does
Packaging gas.
How it's made
Purified from air.
Oxygen is used as a packaging gas in specific situations — for example, in modified-atmosphere packs for red meat, where a high-oxygen atmosphere keeps the meat looking bright red, and in some packaging for fresh produce. It is the same oxygen that makes up part of the air and that we breathe.
Food-grade oxygen is separated from the air by the same cryogenic distillation used for nitrogen and argon: air is liquefied and then fractionally distilled, with oxygen (which boils at a higher temperature than nitrogen) collected as one of the fractions. It can also be produced by adsorption processes that concentrate oxygen from air.
The purified oxygen is compressed into cylinders for use. Unlike the inert packaging gases, oxygen is used precisely for its reactivity in the few cases where it helps — keeping the red pigment of fresh meat bright, or maintaining respiration in some packaged fresh produce — rather than to exclude air.
Possible reactions
Safe.