We’ve put together a list of some of the most frequently asked questions our customers have asked us over the years. Our hope is they shed some light on a widely used but not always well understood product.

What is an oxygen absorber?

An oxygen absorber or oxygen scavenger is a porous sachet that removes the oxygen from the atmosphere. The absence of oxygen prolongs the shelf life of food products. They are commonly used in food packaging to:

    • help retain the original flavour, colour, smell and texture,
    • inhibit oils in foods from becoming rancid, and
    • prevent the growth of oxygen-loving microorganisms such as bacteria, mould and fungi which leads to food spoiling.

What does an oxygen absorber do?

Oxygen absorbers use the available moisture in the food and air to cause the iron particles in the sachet to ‘rust’, thereby removing the available oxygen in the air. The food packaging is then left with a higher concentration of nitrogen, which are better conditions for a longer shelf life.  Trapping the oxygen usually generates a small amount of heat.

When would I typically use oxygen absorbers?

Oxygen absorbers are used in many products, including but not limited to:

    • Pasta and noodles
    • Rice, grain, pasta, seeds & nuts
    • Dried fruits & vegetables
    • Spices, seasonings & herbs
    • Coffee, tea, cocoa & confectionary
    • Processed, smoked & cured meats
    • Bakery goods such as flat breads, cakes, pastries
    • Pharmaceuticals, vitamins & herbal medicines
    • Diagnostic kits & devices
    • Pet foods & Birdseed
    • Stationery and artwork preservation

How do I know if my oxygen absorber is working?

A new oxygen absorber will have a loose powdered feel when pinched. It should feel free of clumps and may feel warm (a by-product of the absorber working in a moist environment).  Spent (or expired) absorbers can feel hard or clumpy to touch.

How long does it take for them to work?

Oxygen absorbers once exposed to the atmosphere begin to get to work immediately. That is why, we suggest that unused oxygen absorbers should be resealed within 15 minutes to ensure the integrity of the product is maintained.

How can I be assured that the oxygen absorbers I received are new and ready to use?

We understand that Protection Experts Australia customers should feel confident they are receiving the best quality products. And that is why all our oxygen absorbers are packaged with a quality check, called the ‘eye’. 

The indicating eye is packaged with the oxygen absorbers and will appear pink showing that the package is sealed and oxygen-free.  Should the eye appear purple, this indicates that oxygen has penetrated the packaging through possibly a puncture or poor seal and the oxygen absorbers have been compromised.  In this instance, we ask that you contact our office immediately so that the problem can be rectified.

Oxygen-free & compromised absorber indicator

I don’t need to use them all, how can I store my oxygen absorbers, so they last?

Store oxygen absorbers at room temperature (5C to 30C), away from direct sunlight. They should be stored in their sealed package or a glass jar with a gasketed lid. Select the smallest glass jar possible to minimise the oxygen the absorbers will remove from the jar. Oxygen absorbers in a well-sealed container will cause the lid to pop down.

The shelf life of an oxygen absorber is up to 18 months.

How long will it take an oxygen absorber to remove all the oxygen from my sealed bag/container?

How quickly oxygen absorbers remove oxygen from the atmosphere will depend on the conditions. In dryer climates, it may take up to a week for absorbers to fully activate.  Warmer, humid climates however accelerate the process and may take only 48 hours for the same result.

I’m using oxygen absorbers, why aren’t my bags getting hard?

Oxygen Absorbers trap oxygen. Given that air comprises 20% oxygen and 80% nitrogen, the absorber will only be removing the 20% of the atmosphere that is oxygen. The volume of nitrogen remaining will mean your bag will not deflate to the extent of the bag becoming hard or rigid.

If I use vacuum packaging or nitrogen flushing to package my goods, do I still need to use oxygen absorbers?

Both these methods are used to remove the oxygen content from a package. Vacuum packaging achieves this by sucking out all air and then sealing the package. Nitrogen flushing forces the heavier nitrogen gas into packaging pushing out the oxygen content.  In both instances, some oxygen remains. It is estimated that when these methods are used there can be 2 – 3% of oxygen remaining. Oxygen Absorbers can then be used to capture the residual oxygen present.

I need to freeze my product. How will that affect the effectiveness of my oxygen absorbers?

Oxygen Absorbers more rapidly capture oxygen at room temperature.

Under normal room conditions (20C) packages will be oxygen-free within 24 hours.  At a temperature of 6C, packages will be oxygen-free within 48 hours.  In 0C to 4C conditions, packages will be oxygen-free within 72 hours.  Given the content moisture levels can differ widely, we suggest customers test for their own unique circumstances.

How many oxygen absorbers do I need?

The factors to consider when calculating how many oxygen absorbers you require are:

    • The volume of the sealed package
    • The volume occupied by the food product.

The oxygen absorber calculation isolates the volume of the food packaging void – sealed package volume less food weight – multiplied by 20%. The factor of 20% reflects that our atmosphere comprises 20% oxygen and 80% nitrogen.

For those who like the numbers, the formula is:

And for those who prefer a shortcut (who doesn’t), check out our online Oxygen Absorber Calculator to find out how many you will need at the click of a button.

What does the expiry date mean on my oxygen absorber?

The expiry date provided is a guide to indicate that for optimal results, the oxygen absorber should be put to use or ‘activated’ by the expiry date. These expiry dates can be up to 18 months from date of production.  Oxygen absorbers can be safely used right up to the date of expiry as they will only be activated once opened and then it will immediately start to oxidise.

The expiry date assumes that over the time of storing the oxygen absorbers they have not been compromised, having remained in the original sealed package away from high temperatures and direct sunlight.

For those instances where you use only a portion of your absorber sachets, the remaining oxygen absorbers should be resealed immediately in a vacuum bag and stored away from high temperatures. It is recommended that these re-sealed packages of oxygen absorbers should be activated within 6 months.

Click here to view a statement from our supplier.

Once placed in position, how long does an oxygen absorber continue to work?

Oxygen Absorbers once exposed to oxygen will immediately start to oxidise, capturing the surrounding oxygen.  This activation period can last between 4 hours to 24 hours.  Once the absorber has completely oxidised, the absorber is no longer working.  This might sound like a problem, however bear in mind that the role of the absorber is to remove oxygen within your sealed package.  Should that package remain sealed, then the conditions within the package will remain oxygen-free. Re-open a package and you will be exposing the contents to oxygen. In this case, the original absorbers should be discarded and replaced with new oxygen absorbers.

There are a couple of variables to consider.

Firstly, how permeable is your packaging? A high barrier packaging solution such as mylar will ensure that oxygen does not pass through to package contents. The lower the permeability of the packaging material (eg paper bag) the more often oxygen absorbers will need to be replaced.

Secondly, oxygen absorbers once fully loaded or ‘spoiled’ no longer have the capacity to absorb additional oxygen. It’s important to therefore make sure that you ‘round up’ when calculating your oxygen absorber needs.

Underestimating your oxygen absorber needs will leave a portion of oxygen within your package causing contents to deteriorate faster over time.

Protection Experts Australia supply a range of oxygen absorbers from 30cc to 500cc.  Contact Us today if you would like to learn more about how oxygen absorbers can work for you.