Using & About Oxygen Absorbers
While owner of AlpineAire Foods in the early 1990’s, I conducted significant research and study into the excellent and very effective technology of oxygen absorbers. Developed in Japan, oxygen absorbers insure a very low residual oxygen level in appropriate storage containers. Through this research and the development at AlpineAire foods, I brought the large scale use of oxygen absorbers into the emergency food and outdoor recreational foods industries.
At that time the goal to achieve for the canning of shelf-stable dried foods was a residual oxygen level of 2% or below. This was the level required by military specifications for long term foods. Oxidation and an atmosphere inhibiting microbial growth were 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 be reduced to 0.1% or less – a significant drop in oxygen levels.
The premier manufacturer of oxygen absorbers, and the one I use, is Mitsubishi Gas Chemical Company, Inc. which produces the “Ageless” brand oxygen absorber. While there are numerous types of absorbers for varied packaging conditions, the appropriate “Ageless” absorber for use with dried foods is type Z.
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 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 talk 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. 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 other careful research by the preparedness planner of trustworthy sources, will produce reliable results.
Determining the size of oxygen absorber
Depending upon the container size and the void area (the area that is the space between the food item) in that container, a number of different sized Ageless sachets are available from size 20 to 2000. IMPORTANT: Ageless 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 equals 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 and you get the “absorption capacity” of each size sachet. An Ageless Z100 will absorb 100 ml of oxygen which is 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 beans would be less.
In general, camping food pouches would 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 there will of course still be in the container an approximately 80% inert nitrogen atmosphere. 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 an “Ageless” oxygen absorber (and other quality absorbers)
- Reduces oxygen in an airtight container down to 0.1% or less to prolong a product’s shelf life.
- It prevents oxidation and mold, bacteria, microorganisms, insect infestation and the like, which thrive in an oxygen-rich packaging environment.
- Done properly, it is simple to use.
- Keeps food products from losing their freshness, color, taste, flavor, wholesome goodness, and important nutritional value when exposed to oxygen.
- 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.
- The oxygen absorber is 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 major component of “Ageless” is powdered iron oxide, an odorless material that in its sachet has no effect on the foods in the container.
- 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.
- A pouch with an aluminum foil barrier as one of the layers is the best.
- 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.
Here is the issue with pouches
Inadequate or faulty seams and rough handling can cause what is known as pin holing or seam breakage. 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 more, can contribute to large or even minute holes and tears. Pouches with oxygen absorbers – for the longest possible shelf life – must be stored and handled properly.
Also keep in mind, 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 has equalized 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 – 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. It is economical and safe to use oxygen absorbers that offer an option to creating an oxygen-free environment that helps 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 used 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 proper size glass container will work.
- Do not pile up absorbers in the tray or holding container. This may cause excessive heat build up.
- Do not remove and use an absorber 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 can not live and 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.
Questions and Answers about the Ageless oxygen absorber from their brochure (may apply to other absorber brands also)
1) Can absorbers be used at low temperature?
A. Lower temperatures slow oxygen absorption rates. However, since product deterioration usually slows down at low temperature while activity of microorganisms also slows down – slower oxygen absorption does not create a problem.
2) Can absorbers be used with vacuum packages?
A. Since the amount of air is already decreased in a vacuum package, a smaller size absorber can be selected. In the case of a strong vacuum ratio, place the absorber into a free air-flow stream, with some distance between the product and packaging film. You use an absorber even in a vacuum package because not all vacuum packing can reduce the residual oxygen as low as an absorber can.
3) Can absorbers be used with gas flushing packaging?
A. Absorbers can be used with a nitrogen gas replacement system. However, this combination will result in a slow rate of oxygen absorption due to the low initial oxygen concentration; therefore, select a larger size absorber to compensate for the delay in oxygen absorption. In addition, gas replacement will tend to result in a fluctuating replacement rate. This is another reason to use a larger size packet. Carbon dioxide gas replacement and mixed carbon dioxide-nitrogen gas replacement are not recommended for use with absorbers, as carbon dioxide will inhibit oxygen absorption.
4) Will the deoxygenation rate be affected by the location in which the absorber is placed in the container?
A. Yes. Generally, an absorber will eliminate oxygen more quickly when placed directly on the product. If available, testing will indicate the best location for an absorber.
5) Sometimes absorbers will heat up during production packaging – is this normal?
A. If the master bag containing a self-reacting type of absorber is left open, or if the individual packets are taken one by one from the master bag, heat generated from the reactions of the absorber may accumulate in the bag, causing the bag to feel hot. Always spread out the packets on a tray to avoid decreased performance. As stated above, 4 hours is the maximum time a Z type (for dried foods) Ageless packet should be exposed to the room atmosphere.
6) I use only a small quantity of absorbers at a time. Will opening and closing the master bag affect the performance of the absorber?
A. Repeated opening and closing of the master bag is not desirable, as it will cause the absorber to repeatedly come into contact with air. We recommend that you divide the packets into small quantities and place these bags – constructed from a high gas barrier material – so as to reduce the frequency of contact between the absorber and the atmosphere.
I hope this article has given you a better understanding and knowledge base on the applications and use of oxygen absorbers. They can be a valuable addition to your overall food storage resources and help keep your investment in emergency and bulk foods fresher and more secure.
Since 1975, Denis Korn has been a leader and trendsetter in the emergency preparedness industry. Mr. Korn is an acknowledged authority on food and water emergency planning and his knowledge of specialty foods and preparedness resources is extensive. He is the creator of PrepareDirect, which specializes in essential emergency and outdoor adventure supplies, and Learn To Prepare, his blog of important and crucial information. He has studied extensively the philosophical, psychological, sociological, and biblical issues that parallel the emergency planning process.
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