If you want to store dry foods for long periods and don’t want to invest in expensive equipment, oxygen absorbers (OAs) are the best option. Oxygen absorbers are cheap, simple to use, and very effective at extending shelf life.
Here is what you need to know about using oxygen absorbers, which foods can be stored with them, and more.
What Are Oxygen Absorbers?
Oxygen absorbers are little packages containing iron powder. When you put the oxygen absorber (OA) into an airtight container, the oxygen molecules “stick” to the iron. OAs can reduce the amount of oxygen in a container to less than 0.01%. (1)
You can make oxygen absorbers in a pinch, although we don’t recommend it.
How Do They Make Food Last Longer?
Oxygen absorbers remove oxygen from in and around food. There are three ways that this helps food last longer:
1. Prevent Oxidation
Oxidation occurs when molecules in the food react with oxygen. The molecules start to break down, causing the food’s taste to change. Oxidation also causes vitamins to degrade, so they lose their nutritional value.
Because oxygen absorbers remove oxygen from the food, they prevent oxidation. The food lasts longer and retains more flavor and nutrition.
2. Stop Mold and Bacteria from Growing
All mold and most bacteria require oxygen to grow. By removing oxygen from the container, these cannot grow on the food.
3. Kill Pests
Pantry pests like moths and weevils are a common problem when trying to store food long-term. This is because the pest eggs are often already in the food when you buy it. If the food sits long enough, the eggs will hatch, and you end up with an infestation in your food.
Pest eggs cannot hatch without oxygen, nor can insects survive without oxygen. So, storing food with oxygen absorbers is an effective way to prevent infestations.
How to Store Food with Oxygen Absorbers
1. Choose your container.
For oxygen absorbers to work for food storage, you must use them in an airtight container. The three most common options are:
- Mylar bags
- Canning jars
- #10 cans
Some people use oxygen absorbers with buckets or vacuum sealer bags. However, these are not reliable because they are prone to leaking.
2. Put food in the container.
Fill the container with food. You’ll want to give the container a good shake to ensure the food has settled, thus reducing the air pockets between the pieces of food.
3. Add oxygen absorbers.
See the FAQs section below for how many OAs to use.
4. Seal the container.
The moment you remove oxygen absorbers from the package, they will start absorbing oxygen. After around 2-4 hours, they’ll have absorbed their maximum oxygen capacity. Thus, you must work quickly with OAs and seal the container immediately.
5. Label and store.
Write down the type of food in the package and the date you packaged it. If you used Mylar bags with your OAs, putting them in a bucket is recommended to protect the Mylar from puncture.
Tip: Put a piece of clear packaging tape over the label. This will prevent the ink from rubbing off!
How Many Oxygen Absorbers to Use?
You’ll need to remove virtually ALL oxygen to keep food safe for long-term storage. Each oxygen absorber packet can absorb a set amount of oxygen measured in cubic centimeters (cc).
You must add the right amount of cc for your package size and type of food. Most foods use 100-150cc for a quart-sized container or 400-625cc for a gallon-sized container.
Note that these are just guidelines. Some foods may require more oxygen absorbers. For example, cereals aren’t very dense and contain a lot of air inside the actual food.
To know precisely how many OAs to use, you’ll need to do some fairly complex math. I’ve included the math in the dropdown for those who are interested.
As Fresh Pack points out, there can be a surprising amount of oxygen within certain foods. For example, dry foods like TVP contain a lot of air. The same goes for dry beans.
They also point out that there is incorrect information about how density affects air amount. The idea that “items with small particles (like flour) are ‘dense’ and have less air volume” is FALSE. Here is why:
“A pool filled with marbles will have the same interstitial air volume as one filled with basketballs. Yes, the basketballs will have much larger pockets of air, but there are far fewer of them. Think of a checkerboard with just 2 large black and 2 large white squares… ½ of its area is black and ½ white. What if it had 100 small black squares and 100 small white ones? 1000? Even with tiny squares, it is still ½ black and ½ white as long as they are all uniform.
What does matter is particle size distribution, or in other words, whether you have particles that are all a uniform size or if you have a lot of particles of different sizes. If you have a pool filled with basketballs AND marbles, the marbles can fill in all the large air pockets. So, products with uniform particle sizes will have more interstitial air than products with a greater distribution of particle sizes.”
Calculating How Much Air is in the Container
To figure out how much air will remain between the food spaces in a filled container, you can do this test:
- Put 1 cup of product in a large measuring cup.
- Add 2 cups of water.
- See how many cups you get in total (the amount won’t be 3 cups because the water fills the spaces between the product).
- Calculate: 3 cups – (how many cups total you got)
- The answer is how much of the product was air. For example, let’s say you got 2.5 cups total: 3 cups – 2.5 = 0.5 cups. Since 0.5 = 50%, 50% of the product was air.
With this information, you can do a reasonably exact calculation of how many oxygen absorbers you need. This requires some more math:
- Figure out how much air your container holds. For example, a 1-gallon Mylar bag holds 3785 cubic centimeters (cc’s). A pint jar contains 100cc of air when empty.
- Determine how much air will be left in the bag once filled by product. For example, if you determined that 50% of the product was air, you’d have 1893cc of air space.
- Only about 21% of air is comprised of oxygen (the rest is mostly nitrogen). So, calculate 21% of your air space. For example: 0.21x1893cc= 398cc.
*Some products like beans contain a lot of air inside of them. For the water test to work, you have to let them sit for at least 6 hours, so they absorb the water. Beans also require a lot more oxygen absorbers than typically shown in charts.
| Food Type | 1 quart | 1 gallon | 5 gallon |
|---|---|---|---|
| Beans, lentils, split peas | 125-150cc | 500-600cc | 2500-3000cc |
| Rice | 100cc | 400cc | 2000cc |
| Flour | 100cc | 400cc | 2000cc |
| Instant mixes and powders | 100cc | 400cc | 2000cc |
| Coffee beans | 100cc | 400cc | 2000cc |
| Pasta | 125cc | 625cc | 2500cc |
| Cereal | 125cc | 625cc | 2500cc |
| Instant potatoes | 125cc | 625cc | 2500cc |
| Whole grains (barley, corn, wheat, oats) | 125cc | 625cc | 2500cc |
Top Tip
It is always best to play it safe – use more oxygen absorbers than you think you need! Using extra oxygen absorbers won’t impact the food. OAs are cheap; better to spend an extra 25 cents on an additional oxygen absorber than throw away 5 gallons of food when it’s needed most.
What Types of Foods Can Be Stored?
Just about any dry and low-fat food can be stored with oxygen absorbers. This includes foods like:
- Flour
- Whole grains
- Pasta
- Dried beans
- Powdered milk
- Cereal
- Freeze-dried food
- Dehydrated foods*
- Nuts and seeds
*Dehydrated foods must be so dry that they snap when bent. Or round foods like corn or peas should shatter when pressed with a spoon.
For more, read: How to Store Dehydrated Foods Long-Term
Foods that Should NOT Be Stored
- Salt: Will become rock hard if stored with an OA
- Sugar: It also will become rock hard; brown sugar also contains too much moisture for storage with OAs. Read how to store sugar for the long term.
- Wet foods: Foods with 35% or more moisture can grow botulism in airless environments. It is recommended that foods stored with OAs have 10% or less moisture to play it safe.
- Baking soda, baking powder, pancake mixes, and yeast: There’s some debate about whether OA can be used with these foods. Some claim that a chemical reaction could occur and result in the leavening products then becoming useless.
Read:
Shelf Life of Foods with Oxygen Absorbers
When done correctly, these are the shelf lives you can expect from foods stored with oxygen absorbers.
| Food Type | Shelf-Life |
|---|---|
| Hard Whole Grains (Dry corn, buckwheat, soft white wheat, durum wheat, spelt) |
10+ years |
| Soft Whole Grains (Oats, quinoa, rye, barley) | 8+ years |
| Professionally-Dehydrated Vegetables | 10-20 years |
| Professionally-Dehydrated Fruits* | 10-15 years |
| Home-Dehydrated Fruits and Veggies* | 2-5 years |
| Freeze-Dried Fruits and Vegetables | 25 years |
| Legumes (Beans, lentils, chickpeas, split peas) | 25+ years |
| White Rice | 10-30 years |
| Brown Rice | 2-5 years |
| White Flour | 10-15 years |
| Whole-Wheat Flour | 10 years |
| Corn Meal | 5-10 years |
| Potato Flakes | 30 years |
| Pasta | 20-30 years |
| Dry Non-Fat Milk | 15 years |
| Cheese Powder | 10-15 years |
| Powdered Eggs | 5-10 years |
| Nuts | 1-5 years |
| Granola | 1 year |
| TVP | 10-15 years |
Important: Temperature Affects Shelf Life
Some foods – especially fatty foods – are very sensitive to heat. Even when packaged with oxygen absorbers, the fats will go rancid if stored in a warm place. While you won’t get food poisoning from eating rancid food, the flavor and nutrition will change.
For this reason, you must keep fatty foods like nuts, cheese powder, and granola in a cool place.
FAQ’s
Q. Do oxygen absorbers cause botulism?
A. Clostridium botulinum is an anaerobic bacteria that only grows in low/no oxygen environments. To help it survive, it produces spores to help it survive. These spores can then create a deadly toxin, which causes botulism poisoning.
Because the botulism bacteria only grows in low/no oxygen environments, it can grow on food packaged in airtight containers with oxygen absorbers.
Botulism requires moisture of 35% to grow. However, virtually all food preservation guides say you should only package foods with 10% or less moisture with oxygen absorbers to play it safe. (2)
This shouldn’t scare you away from self-storing foods with oxygen absorbers. Ensure you aren’t storing moist foods in sealed containers with oxygen absorbers.
The botulism spore is heat-resistant and very difficult to destroy. However, the botulism toxin (which causes the disease) can be easily destroyed by boiling it for 10 minutes.
The CDC states, “Despite its extreme potency, botulinum toxin is easily destroyed. Heating to an internal temperature of 85°C for at least 5 minutes will decontaminate affected food or drink.” This page also has helpful info on deactivating botulism.
Many foods stored for the long term need to be boiled anyway (dry beans, dry grains, etc.), so this, in theory, would kill any contaminants.
This is why botulism poisoning usually happens with home canning (which you generally don’t cook before eating). Botulism poisoning is virtually unheard of with foods that need to be cooked, such as rice, dry beans, etc.
However, that doesn’t mean you should eat any foods which you suspect are contaminated with botulism.
Warning: If the package is bulging (a sign that bacteria or toxins are growing), don’t eat its contents!
Q. What to do with unused oxygen absorbers?
A. OAs start absorbing oxygen the moment you open their package. So, you must plan what to do with unused ones before you begin working. Ideally, you will reseal them in the packaging they came in. Then, vacuum seal them.
If this isn’t an option, you can store unused oxygen absorbers in a mason jar. Fill up any extra space in the jar with marbles (or something similar). The less air in the jars, the less air the unused OAs absorb. Be sure to seal the jar tightly!
Q. How to tell if an OA is still good?
A. If you buy OAs from a reputable company, they should be good. We like the supplier Wallaby Goods; they are good value and provide high-quality products.
They will arrive in a vacuum-sealed package. Most oxygen absorbers have a “margin for error” added to their abilities. So, they will absorb more than specified.
This is so you can have 10-20 minutes to work with the OAs and not have that air exposure count against you.
Here’s how you can check:
- They arrive in a vacuum-sealed package.
- The oxygen indicator is pink or red and not blue.
- The packets feel soft and not crunchy.
Q. Will OAs make the package “suck down”?
A. When OAs remove the oxygen from a container, it can cause the container to suck down as though it was vacuum packed. However, this doesn’t always happen.
Air is approximately 78% nitrogen and 21% oxygen. OAs only remove the oxygen and not the nitrogen (nitrogen doesn’t cause food to spoil). Because the nitrogen is still in the container, it might not look sucked down even though the OAs are working.
Q. What’s the difference between an oxygen absorber and desiccant?
A. Oxygen absorbers will absorb oxygen. Desiccants will absorb moisture. OAs require a small amount of moisture for them to activate. Thus, using both OAs and desiccants together is generally not recommended.
There are some exceptions to this rule, though. Some foods (like home-dehydrated fruits) may contain a lot of moisture. Since moisture is one thing that makes food spoil, adding a desiccant can help the food last longer.
It’s best to use silica gel desiccants in this case because they don’t absorb so much moisture that it will interfere with the OA. Some more advanced types of desiccants can reduce the moisture to practically zero, which means they would stop the OAs from doing their job.
*When using oxygen absorbers and desiccants, put the desiccant on the bottom of the package and the OA on the top.
Q. What’s the difference between oxygen absorbers and vacuum sealing?
A. Oxygen absorbers and vacuum sealing remove air from the packaging. However, vacuum sealing doesn’t remove all the oxygen as OAs do. Also, the vacuum seal bags are not airtight and will slowly leak air into the package over time. Thus, vacuum sealing is NOT suitable for long-term food storage.
Q. Can I use OAs with vacuum sealing?
A. There’s no reason to use oxygen absorbers and vacuum sealing together: OAs do their job well enough without any need to first suck out air.
Further, the vacuum sealer will remove nitrogen from the packaging (oxygen absorbers only remove oxygen). If you add an OA to a vacuum-sealed bag, the bag may get so “sucked in” that sharp edges on foods like rice could tear through the bag.
Q. Can you reuse oxygen absorbers?
A. No, oxygen absorbers cannot be reused. Once they’ve reached their maximum capacity, they won’t be able to absorb any more oxygen. If you open a container of food packaged with oxygen absorbers and want to re-seal it, you’ll need to add new oxygen absorbers.
Q. Should I remove food from its original packaging before storing it with oxygen absorbers?
A. Foods in thin paper bags, such as flour, can be kept in the original packaging. The oxygen absorber can do its job through a paper bag.
For example, you put an entire bag of flour inside a Mylar bag, add OAs, and then seal the Mylar bag.
However, you won’t be able to fit as much flour in the Mylar bag this way. There will also be lots more air space around the bag, so you’ll need to use more oxygen absorbers.
Foods that come in metallic or plastic-coated bags must be removed from their packaging: the OA might not be able to absorb oxygen through this type of packaging.
Q. Do I need to freeze foods like rice and beans before storing them with oxygen absorbers?
A. There is no need to freeze foods before storing them with OAs. The reason for freezing foods before storage is to kill insect eggs in the food. However, since insect eggs cannot hatch without oxygen, there’s no reason to do this step if using OAs.
