Oxygen absorber

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Oxygen supports the growth of microorganisms and causes changes in color and rancid odors in packaged foods. Plastic packaging is less able to exclude oxygen from packaged foods than are the older glass and metal containers. Oxygen absorbers collect any oxygen that might diffuse into a food package.

An oxygen absorber is a packet filled with iron particles and salt that works to retain oxygen. Moisture absorbed by the package combines with iron, salt, and oxygen to rust the iron. This traps the oxygen and usually lets off a small amount of heat. They are used in food packaging to prevent spoiling.

Oxygen absorbers are made in different formulations to match the water activity of the foods they are protecting. The FreshPax Type-D, made by Multisorb Technologies, is designed to be used in dry foods such as nuts and dried grains. The FreshPax Type-B is designed to work with moister foods such as bread and processed meats.

Other technologies are used as well. The Ageless oxygen absorber, as developed by Mitsubishi Gas Chemical, is a sachet of iron (II) carbonate rather than the actual metal powder.