About Oxygen Absorbers
submitted by Denis Korn
I introduced the use of oxygen absorbers into the emergency food and outdoor recreational foods industries in the early 1990s. I did it because oxygen absorbers offer an excellent and very effective technology, developed in Japan, to ensure a very low residual oxygen level in appropriate containers, and it was very easy and relatively inexpensive to use.
At that time, the goal was to achieve a residual oxygen level of 2% or below for the canning of shelf-stable dried foods. This was the level required by military specifications for long-term foods. Oxidation and an atmosphere inhibiting microbial growth are significantly reduced at these low levels. The military specified the #10 can for their long term storage of dried products. By utilizing the appropriate size oxygen absorber, the residual oxygen levels could actually be reduced to 0.1% or less – a significant drop in oxygen levels.
It is important to note that oxygen absorber sachets were designed to be used by industrial manufacturers and packers of food products with the necessary expertise in working with the absorbers. While simple to use, if the absorbers are not handled properly or sized correctly, you have wasted your time and money and have not achieved the expected outcome. I have seen and heard of numerous situations where individuals have inappropriately utilized oxygen absorbers, and they will unfortunately not accomplish the results anticipated. If you are going to use these devices, I recommend following the instructions in this article and talking to those who are educated in their proper use.
Why use an oxygen absorber?
There are essentially two reasons one would use an oxygen absorber – the prevention of oxidation, and the prevention of food damage by infestation. This, of course, helps to increase the shelf life of most foods one chooses for food storage. We'll start by discussing oxidation; infestation is addressed further on in this article.
Oxidation is responsible for the deterioration of foods, including the loss of flavor and taste, discoloration, deterioration and rancidity of fats and oils, texture change, and nutritional loss. Some foods are more susceptible to oxidation deterioration than others. It is important to know how susceptible the foods you are storing are to oxidation, because, as you will see, the type of container you store your foods in may at some point no longer be an adequate oxygen barrier. Unfortunately, the issue of keeping foods in an oxygen-free environment is not easily understood by the do-it-yourself preparedness planner. There is so much misinformation, speculation, confusion, and factual error that the average planner is at a disadvantage in learning the proper techniques. Hopefully this article and others, along with the preparedness planner's careful research of trustworthy sources, will produce reliable results.
Determining the size of oxygen absorber
A number of sachet sizes are available, and the correct sachet will depend upon the container size and the void area (the empty space between the food item particles) in that container. IMPORTANT: The Ageless brand of oxygen absorbers assigns their sizes with numbers that correspond to the oxygen “absorption capacity” in milliliters (ml) – this is the actual amount of oxygen that can be absorbed by the sachet. Other companies may designate their sizes by the “equivalent air volume” in milliliters – this is the total air volume you have in the void area that includes oxygen, nitrogen, and a very small amount of other gases. These are two different figures that it is important for you to know. For your information, 1 gallon is equal to 3,785.4 cubic centimeters.
After you ascertain the void area of your container, you will have determined the equivalent air volume. Since oxygen is approximately 20% of the normal air volume, divide the equivalent air volume by 5 to find the “absorption capacity” of each size sachet. An Ageless Z100 will absorb 100 ml of oxygen contained in 500ml of air volume.
Obviously, a food item that has a large volume or irregular size will produce a larger void in a container; dried mushrooms, large beans, and certain dried vegetables would be an example of this. The void in a container of powders, flours, small grains, and small beans would be less.
In general, camping food pouches use a Z30 or Z50, a #10 can a Z300 or Z500, and a 5 to 6 gallon bucket a Z1000 or Z2000, depending on the size of the food products and the void area.
Because only oxygen is absorbed by these packets, there will still be an approximately 80% inert nitrogen atmosphere in the container. This will cause a partial vacuum effect, meaning that pouches will shrink slightly and become more compact, and in buckets there will be concave effect (top and sides will move slightly inward).
Advantages of quality oxygen absorbers
* Reduces oxygen in an airtight container down to 0.1% or less to prolong a product’s shelf life.
* Prevents oxidation and mold, bacteria, microorganisms, insect infestation and the like, which thrive in an oxygen-rich packaging environment.
* Simple to use (when done properly).
* Keeps food products from losing freshness, color, taste, flavor, wholesome goodness, and important nutritional value.
* Conventional preservatives, antioxidants, gas flushing, and vacuum packing often are not effective because they do not completely eliminate oxygen.
* Conventional and artificial preservatives may be undesirable to many and may produce adverse health affects.
* Oxygen absorbers are safe to use. They have been tested and found to be practically non-toxic. The LD50 Value of the contents is safer than salt.
* The sachet can be discarded through ordinary disposal methods, with no special treatment required.
Selection of a packaging container for use with an oxygen absorber
Of all the issues relating to the use of oxygen absorbers, this is the most confusing and misrepresented among the do-it-yourself group. Remember, absorbers were designed with specific instructions for use by manufacturers and commercial packers.
Points to consider:
* Oxygen absorbers were designed to work when inserted into cans, bottles, and film that offer a variety of airtight characteristics.
* When using cans, make sure there is no leakage along seams. While this container is not as practical to use for the do-it-yourself group, it is without a doubt the most reliable.
* Glass bottles should have a tight seal between the bottle and closure.
* Film pouches must be designed to have a negative to very low oxygen permeability.
* Films have both an oxygen and vapor permeability rating.
* The permeability or rate at which oxygen is transmitted through a film or material determines the length of time the container will remain oxygen free.
* The permeability of metal and glass is zero. It is the seams and closures that determine any leakage.
* The permeability of aluminum foil is zero.
* There are hundreds of combinations of various films for pouches. No single barrier material is adequate for a pouch; it requires a combination of barrier materials to be laminated together.
* Film materials with the proper barrier characteristics must be laminated together to create a pouch that will have a low permeability for an oxygen absorber to work properly.
* The best pouches will include an aluminum foil barrier as one of the layers.
* Pouches with evaporated or coated aluminum are not as good as solid foil.
* While there are various plastic and nylon barriers that have a low permeability, they all will eventually allow the transmission of oxygen, and the oxygen levels in the pouches will increase.
* The oxygen absorber can only absorb so much oxygen, and it too has a limited shelf life.
* A general rule of thumb for a non-solid foil, laminated, high barrier pouch is a 3 year barrier viability life.
* Low barrier pouches have a viability of 3 to 6 months depending on the film material. Think “mylar” balloons filled with helium.
* A laminated pouch with a solid foil barrier is generally between 4 and 7 years.
The issue with pouches
Inadequate or faulty seams and rough handling can cause what is known as pin holing or seam breakage in pouches. The pouch has lost its integrity, and its low permeability rate has been compromised. Excessive folding and squeezing pouches into buckets, too much handling, too much weight on a pouch, sharp food products within the pouch poking through, and other factors can contribute to large or even minute holes and tears. Pouches with oxygen absorbers must be stored and handled properly to achieve the longest possible shelf life.
Also keep in mind that, because the container now has an oxygen absorber, an atmospheric pressure differential has been created (this is the tendency for the inside pressure to want to be equal to the outside pressure). This means there will be an extra “pulling effect” on the seams and closures of the containers to “absorb” the outside atmosphere. This is another reason for proper handling.
Plastic buckets and oxygen absorbers
While plastic buckets are much thicker (70 to 90 mil) than plastic laminated pouches, they are still plastic (polyethylene). Oxygen will eventually be transmitted through the bucket. Depending upon the thickness and seam stability of the bucket, the general rule would indicate a 2 to 5 year barrier viability life. This means that in this period of time, the atmosphere in the bucket will equalize with the atmosphere outside the bucket. Plastic bucket seams are susceptible to the “pulling effect” mentioned above and can cause oxygen seepage into the container. Also, depending upon the environment, plastic buckets will eventually absorb moisture and odors.
TAKE NOTE: Without proper testing and industrial controls, residual oxygen levels in do-it-yourself packaging are based on assumption, speculation, guessing, and probability! If you have access to equipment that tests residual oxygen levels in your container, you may want to consider some spot checking.
How to use an oxygen absorber
Using an oxygen absorber is relatively easy. Make sure you are aware of all the procedures and characteristics of storage, sizing, containers, handling, and other fine points covered in this article. Economical and safe to use, oxygen absorbers offer a way to create an oxygen-free environment, helping to improve shelf life.
Simply put your food in a high gas barrier film package, metal can, or glass bottle, put the appropriate size absorber in the container, and seal the container properly.
Points to consider:
* Depending on the size of absorber, it will take 1 to 4 days to have produced an oxygen free (<0.1%) atmosphere.
* Absorbers are packed in master high barrier bags of various quantities (depending on their size). Check the tightness of the vacuum packed master bag. If you hang the master bag from one end, the packets should not slip. If they do, do not use that master bag.
* After opening the master bag, spread out the needed quantity of packets. The sachets that are not used should be resealed in a master bag or discarded if their exposure to air exceeds 4 hours.
* Remaining sachets should be resealed in the master bag, or another high barrier film pouch or container, after pressing out the air. A well-sealed glass container will work.
* Do not pile up absorbers in a tray or holding container. This may cause excessive heat build up.
* Do not remove absorbers one by one, leaving the master bag open.
* Handle master bags properly and store in a cool (below 85 degrees [F]) and dark place.
* Do not use zip-lock plastic bags or other flimsy containers to store unused absorbers.
* Ideally, if you obtain your absorbers while relatively fresh, use them no later than 6 to 12 months after receipt.
Prevention of damage by microorganisms (mold and aerobic [oxygen dependent] bacteria), insects, worms, and their eggs
* By producing an oxygen-free (<0.1% for the Ageless absorber) environment, live organisms cannot grow and are eradicated.
* Oxygen absorbers prevent the growth of microorganisms.
* The oxygen-free packaging allows you to prevent both adult insects and their eggs from spoiling and damaging foods.
* Testing that utilized the Ageless absorber found that all of the eggs, larvae, pupae, and grown insect of the Rust-red flour beetle, Weevil, Azuki weevil, and Almond moth were killed within 14 days – at 77 degrees (F). The proper container with a zero to very low permeability rate and no holes or seam damage must be used.
The information contained in this article is general and should not take the place of the user’s own application tests. Conditions of use vary depending on the specific applications of each user. The user is responsible for the proper calculations and techniques of absorber application.