Oxygen Removal

“Should the cabin lose pressure, oxygen masks will drop from overhead. Please place the bag over your mouth so we can’t hear you scream.”

Introduction.  Oxygen is vital to life, but it can be quite destructive to some foods, especially over time.  This reaction in foods is called oxidation.  In fats or oils oxidation leads to rancidity.  In other foods oxidation destroys their natural color (think browning of fresh cut apples). Nature protects many susceptible foods by providing a skin or peel.  However, once we start to process these foods we often remove their protections. 

Normal air is approximately 21% oxygen or O₂.  So storage of foods in air susceptible to oxidation results in poor quality storage over time.  Oxygen removal from food storage containers is beneficial in several ways.   It prevents food deterioration from oxidation, prevents growth of some microorganisms and minimizes insects¹. When oxygen levels are maintained less than 1 percent, weevils, moths, and flour beetles are eliminated³. There are several methods to remove oxygen from dry food packages.

Vacuum packaging.  Vacuum packaging is used to first remove air from a package by a vacuum and then seal the bag before any air can re-enter.  Generally, the longer the food storage shelf life the greater the vacuum needed.  No credible research could be found related to vacuum packaging machines and food storage.  Without getting into a technical discussion, vacuum food savers are usually priced in relation to their ability to create a better vacuum.  Models costing less than $100 will suffice for shorter term food storage (1-2 years) and models costing $300-$1500 may be needed to remove enough oxygen for quality storage over 5-30 years. 

Modified atmosphere packaging.  This is a more complicated method of vacuum packaging where a replacement gas is added after vacuum removal of air.  The replacement gas can be any mixture of nitrogen or carbon dioxide.  Since this method requires specialized equipment not typically available to home food storers, it is not further discussed here.  Like vacuum packaging, this method should only be used for completely dry foods for emergency food supplies.

Oxygen absorbers/scavengers. Oxygen absorbers are packages of iron powder or filings.  The iron combines with residual moisture and oxygen in the food package to cause rusting or oxidation of the iron⁴.  In this event the oxygen is bound to the iron and can no longer oxidize foods.  With the use of oxygen absorbers, oxygen is removed throughout the product and package being stored.  Oxygen absorbers can reduce the levels of oxygen in packaging to less than 0.01 percent.  However, it must be noted that this low oxygen level can only be maintained in packaging specifically designed to prevent the transfer of oxygen across it.  Examples are metal cans or mylar™-style metal foil-plastic bags.

Oxygen absorbers are not edible, but they are not toxic¹⁰.  In addition to iron, most will contain some activated charcoal and salt.  All of the ingredients are encased in a paper wrapper that can be placed in contact with foods.  Oxygen absorbers are available in many brands and these should be roughly equal for their intended use.

Use. Oxygen absorber packets are made for different moisture levels of foods.  Select one made specifically for use in dried foods (assuming emergency food storage is mostly dried foods).  Once purchased store them unopened in their original package.  Once opened they will begin absorbing oxygen in 20 minutes and quickly lose effectiveness and may be spent in approximately 5 hours¹¹. 

Packets usually come in cubic centimeter (cc) sizes of 100 cc, 300 cc, or 500 cc sizes.  These are meant to absorb oxygen in that number of cubic centimeters.  Typically one 100 cc packet is used for pint or quart jars and small foil bags of the same size.  One gallon foil lined bags or #10 cans may need the 300 cc size.  Five gallon buckets will need 500 cc.  One 500 cc pack or 5 – 100 cc packs will work^8,9.  Keep in mind that plastic buckets will permit oxygen to penetrate over time⁴.  So, oxygen absorbers will work to kill insects, but over time will not prevent food oxidation. Oxygen absorbers cannot be reused.

Dry ice. Dry ice is frozen carbon dioxide.  It is not a very effective method of removing oxygen from food packages.  Instead it is often used an insect treatment^4,9.  This use is discussed elsewhere.   

Hand warmers. At least a few people are recommending hand warmers for oxygen absorption.  They theorize that the ingredients are the same.  However, this is akin to using a toilet plunger for a baseball bat.  They both are wood.  Yes, it will “technically” work somewhat, but it may not work well.  And, the product is simply not made for that use. 

References

[iii] Broderick, S., Lloyd, M., Ogden, L., Pike, O. 2010.  Feasibility of re-using PETE soda bottles to exclude oxygen during storage of low moisture foods. BYU Department of Nutrition, Dietetics and Food Science. Available online at: http://ndfs.byu.edu/Portals/9/docs/research/long/PETE%20bottles%20paper.091910.pdf

[iv]  Thompson, J. Dry-Pack Food Storage: Container Options, Oxygen Absorbers and Other Treatment Methods. Available online at: http://extension.usu.edu/weber/files/uploads/J%20Thompson%20Handout1.pdf

[viii] Packaging Technology. Technology Watch 4 (1). Available online at: http://www.wellnesswest.ca/dmdoc/TW_ActivePackaging.pdf

[ix] Thompson, J. Dry-Pack Food Storage: Container Options, Oxygen Absorbers and Other Treatment Methods. Available online at: http://extension.usu.edu/weber/files/uploads/J%20Thompson%20Handout1.pdf

[x] 2010. Study of the Use of Oxygen-Absorbing Packaging Material to Prolong Shelf-Life of Rations. Defense Logistics Agency Combat Ration Network for Technology Implementation-II. Available online at: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA528259&Location=U2&doc=GetTRDoc.pdf.

[xi] Oxygen Absorbers. The Church of Jesus Christ of Latter-day Saints. Available online at: http://providentliving.org/pfw/multimedia/files/pfw/pdf/109616_OxygenAbsorbers31_MAR_08_pdf.