Oxygen Absorber Packets
A Short Lesson On Oxygen Absorbers
Within the last ten years the advent of oxygen absorbers has brought a revolution to the food storage industry. Their use has increased the storage life of foods and has made the job of putting away food for long term storage much simpler. There are two types of oxygen absorbers used for the storage of Food, "B" absorbers and "D" absorbers. The "B" absorbers require moisture from the food they are packed with to perform their action. A good example would be beef jerky or dehydrated fruit that hasn't been dried until it is brittle. The "D" absorbers contain their own moisture and are better suited for dry pack canning because there isn't enough moisture in correctly dried food to activate the "D" absorbers. The "B" absorbers will last a year after they are manufactured but the "D" absorbers only last 6 months. This is important for you to know so you won't buy a bunch of absorbers, pack them away for two years, and expect them to do their thing when you finally open them. The "B" absorbers also work much slower as they must first absorb moisture from the food they are packed in before they will absorb any oxygen. You can generally leave them out for 2 hours before they reach their advertised minimum absorbing capacity. Because the "D" absorbers have their own moisture built into them, they start absorbing oxygen immediately when opened and reach their advertised minimum much quicker, generally within 20 minutes. Oxygen absorbers perform their action through a chemical reaction. They contain iron powder which reacts with the oxygen in the air causing the iron powder to rust. When all the iron powder has oxidized, the oxygen absorbers are "loaded" and the absorbing action stops. Remove the oxygen from an active absorber and the chemical reaction stops. Put them back in the air and the reaction starts again until the iron is gone.
Number of oxygen absorbers needed: We sell 500cc absorbers. They will absorb 500+ cc of oxygen. A #10 can holds 13 cups or very roughly 3300cc. Air is 21% oxygen. So that empty 3300cc #10 can actually has about 683cc of oxygen in it. If you take a full cup of beans it takes about 0.375 cups of water to bring the water level up to the top of the cup. I've found this to be true with most of the whole seeds I've measured including wheat and rice. This figure is important because it also tells you how much air is in the can when it is full of seeds - 37.5%. With a #10 can full of these products, you now have about 256cc of oxygen left in the can. If you are canning a powder you probably have less air than this but foods like macaroni would have more. Already you can see that one 750cc absorber should do the job nicely, in fact it's a bit of overkill. A 300cc absorber would also do the trick. We use one 500cc absorber in each of our #10 cans as we'd rather have a bit of overkill than a little oxygen left in the can should the absorber become loaded. Actually, on the cans, this is a lot of overkill as the absorbers we use now actually have more than twice as much oxygen absorbing capacity as what they are rated for. A 6 gal bucket holds 22,740cc. Going through the above calculations, a full 6 gal bucket of grain or beans has about 1791cc oxygen left in the container at sea level. You will need four of our absorbers if you are packing up your food at lower elevations. Our facility is at 6,000 feet and at this altitude there is only an equivalent of 1484 cc of oxygen in the thinner air. Again, because of the oxygen absorber's significant under rating, we only use two 500cc absorbers in the buckets as they will absorb more than twice their rated capacity Oxygen absorbers are over rated to give you a fudge factor if you should leave them out in the air too long. Generally, you have about 20 minutes before they reach this advertised minimum. There are variables that determine how fast the oxygen absorbers work, so you shouldn't leave them out any longer than you absolutely have to. But why not get every bit of absorption you can out of them? May I suggest you leave only enough out in the air to take care of maybe 1 or 2 minutes of operation? The following test was made with Fresh Pax D750 absorbers. How do you know when an oxygen absorber is spent???
The rest of this page is an excerpt from: Use of Oxygen Absorbers in Dry Pack
Canning At the Benson Quality Assurance Laboratory Conclusions: Oxygen absorbing packets are effective in reducing oxygen contents in sealed cans. The ageless Z300 packet has a greater than claimed capacity for absorbing oxygen. Packets abused by 4 hour-exposure-to-air still exceed claimed capacity. It may be economical to use smaller packets based on the dead air volume instead of can volume. Smaller packets would have less tolerance for abuse and personnel would need to be more diligent in protecting the packets. The level of oxygen remaining in the presence of the absorber packets is sufficiently low to greatly retard development of rancidity. The biological consequences are not so easy to predict. Microorganisms range from aerobic to anaerobic, thus no unqualified statement can be made. The energy requirements of anaerobic bacteria are met by reactions between oxygen and more than one other molecule. This makes bacterial energy a higher order of reaction than rancidity. Thus, the rate of bacterial aerobic reaction would be more seriously retarded than rancidity. These matters are not of practical importance because the products to be canned should be too dry to support microbial growth. Insects are aerobic and would like-wise suffer retardation of activity. No comprehensive statement can be made about irreversible inactivation or death of insects. As long as the oxygen level remains low, insect activity will be lower by at least the square root of oxygen content. In a practical sense, these packets are effective in stopping insect activity. USDA does not recognize any method except disintegration as effective for completely killing insect eggs. Table 1: Key to Table 2
Name Description
-----------------------------------------
Blank Air sealed in a #10 can (No product)
Fresh Air + Fresh packet (Exposed less than 5 min)
X Air + Exposed packet (Exposed 4 hours)
O Product sealed in can with no packet
Milk O Dried Milk only
Milk Fresh Dried Milk + Fresh packet
Milk X Dried Milk + Exposed Packet
Mac O Macaroni Only
Mac Fresh Macaroni + Fresh packet
Mac X Macaroni + Exposed Packet
(Exact measurements couldn't be duplicated in subsequent tests) Table 2: OXYGEN AND NITROGEN CONTENT OF ------------------------------------------------------
% of O2 | % of N2
--------- | ---------
48 1 2 | 48 1 2
Sample hours week weeks | hours week weeks
|
Fresh 0.70 0.42 0.43 | 98.36 98.65 98.65
X 2.27 0.40 0.90 | 98.74 98.67 98.55
Mac O 20.05 20.18 19.98 | 79.11 78.81 79.19
Mac X 0.42 0.42 0.42 | 98.64 98.20 98.66
Mac Fresh 0.45 0.41 0.41 | 98.63 98.66 98.65
Milk O 20.33 19.99 20.14 | 78.72 79.02 78.99
Milk X 0.50 0.43 0.27 | 98.57 98.63 98.62
Milk Fresh 0.48 0.44 0.43 | 98.59 98.63 99.27
|
Oxygen absorbers come in a plastic bag. Each
absorber packet has a special barrier to prevent it's contents from making contact with
your food. 
Each bag of oxygen absorbers contains a
light pink capsule. This capsule turns to a light blue color when the bag is opened. It's
there to tell you if an unopened bag has been compromised. It doesn't automatically mean
that all the oxygen absorbers inside are bad as it will change color soon after the bag is
opened.
Generally, oxygen
absorbers have a greater capacity than is listed on the package. This is intentional to
allow for some exposure of the packet to air during your packaging process. None of this
is necessary if you have a new, sealed bag of oxygen absorbers. However, if for any reason
you want to check them, this is one way to get it done.
It’s impossible to see how much
life is left in an absorber by looking at it or feeling it. The only sure way is to
actually see how much oxygen it will absorb. One way to do this is to tape the absorber to
the bottom of a bottle. The larger the bottle the better. In my tests I used a gallon
pickle bottle. Put the bottle upside down inside a pan of water being careful to set it
straight down so no water enters the bottle. As the days pass and the absorber takes in
oxygen, the water level will rise in the bottle. When it stops rising, use a magic marker
and mark the water level, then take the bottle out of the water and fill it with fresh,
new air. I did this by blowing 5 or 6 full breaths of air into the bottle. Then sit it
back down into the water. When the water level stops rising again, mark the level again
then fill it with new air and repeat the process until the absorber won't pull any more
water up into the bottle. 
In my tests it took 3 1/2 cycles for the
D750cc absorber to get loaded using a 1 gallon bottle.