Monday, September 3, 2012

Oxygen Absorbers

Most of us have heard about or already use oxygen absorbers, but for those who haven’t had the opportunity to use them, here are a few facts about them.

What Are and How Do Oxygen Absorbers Work?
Oxygen absorbers simply consist of a small packet made of breathable material containing iron powder which reacts with the oxygen in the air causing the iron powder to rust. It is the rusting reaction that consumes the oxygen molecules.

When the oxygen in the food storage container has been absorbed, the oxygen absorber ceases working because all the oxygen in the container has been absorbed.

Or they become "loaded" when all the iron powder is completely rusted the absorbing action stops. For this reason it is important to select the proper size oxygen absorber for the container or Mylar Bag being used. Selecting an absorber that is too small for the container volume will not have enough iron powder in it to consume all the oxygen in that container and your long term storage may be compromised.

How much oxygen does an absorber absorb?
All absorbers specify the amount of oxygen each packet can consume in “CC’s” (cubic centimeters). Again this is the amount of oxygen the absorber will consume, not the total amount of air in the container. There is only 21% oxygen in the air we breath and the rest is mostly nitrogen and will not harm the food being stored. So you simply calculate how much oxygen in cc’s you need to remove and use the appropriate size absorber. For more information about how to calculate those volumes visit:

I took a photo of new and used oxygen absorber contents of the same manufacturer.
The first photo shows two piles of absorber contents on a plate. The pile on the left is a fresh (black) absorber contents and the pile next to it on the right side (red or rust) is from an absorber taken from the #10 can of Vital Wheat Gluten I recently opened.

This photo shows the two absorber packets I opened and emptied for the first photo.

‘FreshUs’ brand Manufacturers Statement:
FreshUs is oxygen absorber to protect packaged foods and other products against spoilage, mold growth, color change, loss of nutritive values, insect damage and loss of quality. By removing residual oxygen inside packaging to below 0.01% FreshUs effectively preserve packaged foods without use of food additives and preservatives. FreshUs not only extends shelf life but keeps product quality as was.

Compared to other packaging methods FreshUs shows better performance than nitrogen flushing or vacuum packaging. FreshUs can replace or combine with these conventional Gas Flushing or Vacuum and back flushing methods to ensure product quality and extend shelf life.

FreshUs reduces and maintains Oxygen content in packaging to below 0.01%.
Thereby eliminates Aerobic Microbial Growth and Oxidative Chemical Reactions in Packaging.

How Long Does it Take For the Oxygen Absorbers to Work?
Oxygen Absorbers become warm to the touch when they are working. They take about 4 hours to achieve their rated maximum absorption.

Are They Dangerous to Come in Contact with Food?
The packets are made of a breathable material that allows oxygen and moisture to enter but does not allow the iron powder to leak out. The Oxygen Absorbers are safe to place on top of the food. The packet material will not harm the food they are in contact with.

How I use Oxygen Absorbers:
After years of storing dry bulk food for myself, I have simplified the process and size of the absorber (I like simple). I now use and keep in stock the 500cc size only and use multiple packets where needed.

The food amounts I now store in are:
1 quart in quart canning jars.
1 gallon in 12.5 x 18 x 4.3 mills size Mylar Bags.
5 gallons in 20 x 30 x 4.3 mills size Mylar Bags.

The number of absorbers I use:
1-500cc absorber in each quart canning jar.
1-500cc absorbers in each gallon Mylar bag.
5-500cc absorbers in each 5 gallon Mylar bag.

Placing too many absorbers in a container is perfectly fine, because when the oxygen is gone they stop working. This gives an added insurance policy if you are in doubt as to the size of absorber to use for the particular food being stored.

Note: It is recommended that you do not use a desiccant with oxygen absorbers. Absorbers require some moisture to work (rust).

I purchase my absorbers from Honeyville Grain in 75 count packages.


  1. Great advice! I went searching on the internet to determine how many oxygen absorbers I needed for packing up 5 gallons of in mylar bag a while back.

  2. This was such a neat explanation that it jogged my memory back probably 50 year to a bag of Gordon's potato chips. They weren't sealed in plastic like now but some kind of wax paper I guess, anyway they had a small bag of black powder in each chip bag. I got told not to eat the bag as it was poison, everything was poison and to be left alone in those days. So after much research I finally found where the bag contained activated charcoal that kept the chips fresh much in the same way a modern oxygen absorber does though not a good for sure. It was put in to absorb the smell from something they were putting in the cooking oil to keep things fresh but was found to keep the bag fresh on it's own. No wonder everyone got cancer, hard to tell what was in the oil that they didn't want us to smell.

  3. How to you store the rest of the absorbers in the big bag until you need them?

    1. I simply reseal them in the same bag they came in!