Mylar and Oxygen Absorbers

What are mylar bags and oxygen absorbers?

Mylar bags are metalized plastic pouches that block light and slow the movement of air and moisture. An oxygen absorber is a small packet that takes up oxygen from the air sealed inside a container. Together they lower the oxygen that supports insects, mold and rancidity in dry food.

They protect the quality of food that is already dry and clean. They do not make a wet or unsafe food safe. Many people hear about these products from videos or friends who describe very long storage lives. Treat those claims with caution. Storage life depends on the food, how dry it was, how clean it was, and the temperature where it is stored. Ask your extension office what current research supports for the foods you want to store, instead of relying on a number you cannot verify.

Which foods are suitable?

The usual advice is to use them for dry, low-moisture foods such as whole grains, dry beans, white rice and pasta. Foods with high moisture or oil content raise real safety concerns. Moist foods stored without oxygen can allow the bacterium that causes botulism to grow.

Brown rice, nuts, whole-grain flours and anything oily have limited storage lives whatever you do. Do not use these methods for fresh, moist or home-dried foods unless a tested source says it is safe.

• Dry, low-moisture grains and beans suit the method
• Moist or oily foods raise safety concerns
• Home-dried foods need a tested source first
• Never use it to try to preserve moist or fresh food

Why does moisture matter?

Without oxygen, certain bacteria can grow if the food has enough moisture. Dry foods are protected because there is not enough water available. If a food is not dry enough, sealing it in an airtight, low-oxygen package may create the very conditions that those bacteria like.

Check the moisture level of your food by a method your extension office recommends, and buy food from sources that keep it dry. Do not guess.

How do you use absorbers safely?

Follow the maker's instructions for the size and number of absorbers for the volume of your container. Keep unused absorbers sealed, because they start working as soon as they are exposed to air and can be spent quickly. Work in small batches so you are not leaving packets open while you fill bags.

Absorbers are not food. Keep them out of reach of children and pets, and do not let them mix with food. Dispose of them as the maker advises. Keep a log of each bag: the food, the date, the number and size of absorbers used and the shelf where it is stored. When you open a bag, note how the food looked and smelled. Your own records are the best evidence of how the method works in your home.

How do you seal and store the bags?

Fill the bag, add the absorber, press out excess air as the maker directs and seal the bag fully. Check the seal. Many people place the sealed bags inside a food-grade bucket with a lid, which protects against rodents, punctures and crushing.

Store in a cool, dry, dark place. Label each bag with contents and date, and note on your inventory where it is. Keep a small supply of spare bags, clean scoops and a sealing tool in one place, so you are never tempted to leave a half-filled bag open while you hunt for supplies.

How do you check stored bags?

Look at the bags from time to time. A bag that has swelled, leaked, smells odd or shows moisture inside should be treated with caution. Do not taste food to test it, and discard food you doubt. Packages should usually look tight and snug around the food after the absorber has done its work.

Dispose of suspect food where people and animals cannot get it. If you have any doubt about a stored bag, do not open it near children or pets, and do not taste the contents. Ask your extension office what to do. The cost of discarding a bag of grain is small compared with the cost of an illness.

Where can you get tested guidance?

The National Center for Home Food Preservation and your county extension office can tell you what current research says about oxygen-free storage and which foods are suitable. Ask them before you try a new food or method. Do not rely on videos or forum posts for safety.

Last reviewed: November 12, 2026. Written by the Homestead & Small Farm Editorial Team. See our editorial policy.