how to tell if oxygen absorbers are still good

Knowing if oxygen absorbers are still good can help you use them correctly. The truth is that most people may not know what oxygen absorbers are until they see one.

Oxygen absorbers are used to reduce the amount of oxygen present in sealed packages. They aid in preserving the quality and freshness of products for longer storage periods.

But they work only if they are good, and that is why it matters to know, “how long do oxygen absorbers last once opened?”

An oxygen absorber is still good if it becomes warm in your hand or the oxygen indicator on the packet is not purple.  

Learning More about Oxygen Absorbers

Oxygen absorbers are tiny packets filled with salt and iron powder, and are used to keep perishable foods fresh for longer.

pouring salt from glass jar

There has been a dramatic shift in the food storage sector due to the development of oxygen absorbers over the previous decade. Their use has significantly improved the time that food can be stored.

These packets can absorb oxygen and create a 0.01% oxygen atmosphere. And that is why they are quite powerful in so many ways.

For instance:

  • They keep foods from going rancid
  • They maintain their original colors
  • They slow the spread of bacteria and fungi
  • They deter pests from invading food storage containers.
  • They improve the qualities of oils and fats.
  • They prevent discoloration in foods.
  • They eliminate the need for BHA, sulfur dioxide, and additives.

All Are Oxygen Absorbers the Same?

No, they are not.

You can now find wide different varieties of oxygen absorbers, making them useful in different situations. They may contain different stuff based on their intended purpose as well as the moisture present in the product. 

 Types of Oxygen Absorbers

dried fruits in a jar

As mentioned, you can find different types, but two of them are probably more common.

  • B Absorbers
  • D Absorbers

In order to work, “B” absorbers must absorb moisture from the food they are stored with. For instance, you can use them for beef jerky and dehydrated fruit that has not been dried to the point of being brittle.

On the other hand, the “D” absorbers become more suitable in situations where there is not enough moisture to begin with. And that is why they work better for dry-pack canning. 

How Do Oxygen Absorbers Work?

The oxygen absorber might be part of the packing film or structure, or it can be packaged separately.

powdered iron

These absorbers often use a blend of iron powder, activated carbon, and sodium, which is quite useful in improving the quality of most items.

The principal ingredient is iron powder, while salt serves as an activator to initiate the rusting process. This in turn effectively reduces the oxygen content in the environment to around 0.01% when used correctly.

This is not a quick process; the packets may take up to 4 hours to reach their absorption rate.

In other words, they keep absorbing oxygen until the iron has fully oxidized.  The reaction stops after that and oxygen absorbers are no longer useful. 

How to Tell If Oxygen Absorbers are Still Good?

When oxygen absorbers have been opened, it is important to use them right away and not keep them for later.

So, how to tell if my oxygen absorbers are still good? The fact that an oxygen packet warms up indicates it is doing its job.

food storage

Some can get so hot that they are painful to touch when continuously exposed to oxygen, and they frequently generate condensation on the inside of the outer container.

You can check how quickly a bag of absorbers heats up by taking one out and placing it on a flat surface like a table, carpet, or chopping board.

Tip: Keep in mind that absorbers may not always warm up, especially in dry conditions, but the success rate of most oxygen absorbers is absurdly high. 

The Oxygen Indicator Method

When you buy absorbers packs, you will notice that they come with an oxygen indicator.

Paying attention to its color is a good way to tell if they are still good enough.

labelled storage jars

Of course, it is not the most reliable method to confirm if an absorber is working, but it will give you a good idea of the bag’s overall health.

The only real issue is that the manufacturer’s application of dye is inconsistent. As long as they are not a deep purple shade, ones ranging from very light pink to dark pink should work just fine. 

Use in the Package Method

What it means is that you can check if a bag of oxygen absorbers is still good by using one in the food storage bag. 

packed foods

You can tell if they are doing their job because the air within the bag will significantly decrease, giving it a “vacuum-packed” appearance.

Remember, the removal of oxygen is more important than achieving a perfect vacuum seal. Therefore, do not worry too much if the bag does not appear completely sealed. 

But, you have to use enough considering the size of your food bag and the food type to get the best results. 

An Important Consideration

Most of the time, a weakened bag seal is to blame for an “oxygen absorber that fails.”

coffee beans packed in mylar bags

When sealing the typical1 gallon bag, leave at least 2 inches of space. If you iron a Mylar bag, you will find countless tiny seams that could act as “straws” to let air in.

It means it is a good idea to use a thick seal to make sure no air leaks through.    

How Long Will Oxygen Absorbers Last in General?

In most cases, the absorbers come in airtight and moisture-proof packaging that keeps them effective and used for up to two years if they are not opened.

dried apples in a jar

As their efficiency reduces when exposed to oxygen and other pollutants, the absorbers should be utilized as soon as possible after opening.

After being opened, oxygen absorbers only have a limited shelf life (usually a few days).

The shelf life of oxygen absorbers in their original packaging is at least six months, but they may also be usable for up to a year.

Once an absorber’s packaging has been opened, you have around 15 minutes to utilize it.

Tip: It is possible to keep unused packets for up to six months if you store them in a PETE container or a regular airtight glass jar. 

Why Do Oxygen Absorbers Spoil?

When an absorber’s iron has completely oxidized, we say it is “loaded,” or spoilt.

Since oxygen only accounts for about 20% of the composition of air, the oxidation of 1g of iron may be able to absorb 300 cm3 of oxygen from its surroundings. It roughly equals a volume of air of 50oz.

spoiled strawberries

You can save money by using a hand warmer instead of numerous smaller packets in a larger bucket if you want to remove all of the oxygen from the container. 

But, keep in mind that it is not always recommended because hand warmers are not exactly food safe.

Tip: Be sure to utilize oxygen absorbers while storing grains, rice, and wheat to maintain their quality over an extended period. 

What Causes Oxygen Absorbers to Go Bad?

The surrounding temperature and humidity can alter oxygen absorbers’ effectiveness.

moisture from window glass

The thing is that gases can easily travel through activated carbon (C), also known as activated charcoal and react with the available carbon.

Most pollutants and impurities are adsorbed by the carbon as the gases react with it.

If you open an oxygen absorber and do not use it in a container, it will already start to suck oxygen from its environment. 

And remember, it is good for as long as the iron in the package does not oxidize completely. 

Are Oxygen Absorbers Useful in Ziploc Bags?

Technically, you do not need to use oxygen absorbers in vacuum-sealed bags because they are designed to keep air or oxygen out. The same thing happens with Ziploc bags.

packed vegetables in a ziplock bag

But, if you still want to use oxygen absorbers with these bags, you can certainly try. Still, it is important to keep a few things in mind.

For instance:

  • Be sure to use a heavy-duty Ziploc bag.
  • Ensure that the bag is sealed perfectly to keep oxygen out.
  • Consider using several layers of bags to prevent oxygen from entering.

It means that so long as you ensure that oxygen does not enter the bag, the absorbers will do their job just fine.

Tip: It is important to not ingest oxygen absorbers because they are usually safe but are not edible. 


woman packing foods

Learning how to tell if oxygen absorbers are still good can help you store your food longer.

Remember, any dry, home-packaged food should contain oxygen absorbers to improve its shelf-life.

But, these absorbers are only going to work if they are still good. And that usually means using them within minutes of opening them.

Be sure to check if they become warm in your hand to ensure they are working just fine.