# A Short Lesson On Oxygen Absorbers
> 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.
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. 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. Number of oxygen absorbers needed: We sell 750cc absorbers. They will absorb 750+ 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 the 750cc absorbers in the #10 cans as we'd rather have a bit of overkill than a little oxygen left in the can should the absorber become loaded.) Checking the same thing with a full 6 gallon bucket of grain or beans, you will have 1890cc oxygen left in the container at sea level. You will need three absorbers. We can get away with using two absorbers because 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. Be aware that absorbers are over rated a little bit to give you a fudge factor if you should leave them out in the air a bit too long. Generally, you have about 20 minutes before you 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 5 minutes of operation. The absorbers you are about to use should be laid out side by side so they are not touching each other. The reason for this is because as they work they generate heat and the hotter they are the faster they will absorb oxygen. (No, I don't suggest you keep them in the refrigerator.) The goal is for them not to absorb any more oxygen than is necessary before they are sealed into the storage container where you want them to do their thing.
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