The short answer

Mylar-type foil bags block oxygen, light and moisture, and oxygen absorbers remove the oxygen left inside, so dry foods like white rice, wheat, oats and dry beans keep for years. It is only safe for dry food: Utah State University Extension says food should be below 10% moisture, and warns that storing high-moisture food in reduced-oxygen packaging can result in botulism poisoning. Use the right absorber size, work fast once the absorber pack is open, seal completely, label, and protect the bags from rodents.

Key numbers

• Below 10%moisture content for food stored with oxygen absorbersSource: USU Extension fact sheet
• 15 minutesuse absorbers within this time once their package is openedSource: USU Extension fact sheet
• 300 ccabsorber for a gallon container or #10 canSource: USU Extension fact sheet
• 3 × 500 ccabsorbers for a 5-gallon containerSource: USU Extension fact sheet

How it works

Mylar: USU: “One trade name is Mylar and its often used as a generic name” for foil laminate pouches; “The foil layer dramatically reduces the transmission of oxygen and moisture through the film,” and the inner layer “is food-grade plastic with no known toxicities.” Oxygen absorbers are, in USU’s words, “small packets of iron powder and salt used to prolong the shelf life of food”; moisture makes the iron rust, which removes oxygen, bringing it “to .01% or less.” USU lists what that does: “Delay the discoloration in foods,” “inhibit oils from becoming rancid,” “help to retard the growth of microorganisms such as fungi,” and “prevent infestation.”

Which foods are suitable

USU: “Products that are low in moisture and oil are best for use with the absorbers.”

Foods USU names: its fact sheet lists “baked goods, nuts, coffee, processed food, seasonings, flour, grains” and dehydrated foods among the foods absorbers are used with; its food-specific pages cover white rice (25 to 30 years sealed), wheat and dry beans (10 or more years with oxygen removed).

Mixed guidance: USU’s 2011 oxygen-absorber fact sheet lists “wheat, beans, corn and peas” as not oxygen-sensitive, but USU’s current dry-bean guidance says “oxygen absorbers should be used to remove oxygen from the packages to extend shelf life and minimize off-flavors,” with 10 or more years in #10 cans or Mylar-type bags. Both are USU statements, with the bean page the more recent and more specific. USU’s wheat guidance: an oxygen-free atmosphere “will kill adult insects and prevent larval insects from surviving,” and “It is not necessary to store wheat in the absence of oxygen unless insects are present.”

Oilier foods: USU’s fact sheet says absorbers “inhibit oils from becoming rancid” and that low-oil products work best; North Dakota State University’s pantry chart gives whole wheat flour 3 to 6 months and brown rice 1 to 2 years in ordinary packaging (see Long-Term Food Storage). No USU page read gives a sealed-with-absorber shelf life for these foods.

Outside the method: any food not known to be below 10% moisture (USU).

What you need

The method uses these items:

• Mylar-type bags.
• Oxygen absorbers in the right sizes, sealed in their original package until use.
• A heat sealer suited to foil pouches (follow the bag and sealer maker’s instructions).
• A food-grade bucket or bin with a lid for rodent and crush protection.
• A permanent marker for labels.

Absorber sizes

USU’s guidance:

Container	Oxygen absorber
Quart	one 50 cc
Gallon or #10 can	300 cc
5 gallons	three 500 cc

These are USU’s sizes per container; for other sizes, the absorber maker’s chart is the reference.

Step by step

The timing rules come from USU; the sealing steps are the bag and sealer makers’ instructions.

1. Fill the bags first, so the absorbers are opened last.
2. Open the absorber package last. USU: once the package is open, “use within 15 minutes”; “Store the unused packets in an airtight glass jar or PETE container for up to 6 months.”
3. Add the absorber and seal as the bag maker and heat-sealer maker direct.
4. Check the seal along its full width; repack any bag that is open.
5. Label with contents, date packed and absorber size.
6. Protect the bags in a rigid container: USU says rodents “can easily chew into” a bag even with a metallic layer, and its storage conditions are approximately 40 to 70°F, low humidity, out of direct sunlight.

USU describes a spent absorber as brown and clumped, against a new one’s “fresh pink or gray powder.”

Vacuum sealing is not the same thing

USU: “Vacuum Packaging Foods can increase the shelf life of some foods, but it is NOT a food preservation method by itself”; “vacuum packaging will increase the ability of the botulism bacteria to grow by removing oxygen”; foods that needed refrigeration or freezing before vacuum sealing must still be kept that way afterward. USU also notes that plastics “will allow significant oxygen levels into the container in 1 to 2 years,” while foil pouches and metal cans are its long-term oxygen barriers.

Common questions

Can I put rice in Mylar bags with oxygen absorbers?

USU: “When properly sealed and stored, polished white rice will store well for 25 to 30 years,” and at a constant 70°F with oxygen absorbers “for up to 10 years.” The same page says: “After opening use rice within one to two years.” USU’s rice page does not give a figure for brown rice.

How many oxygen absorbers do I need for a 5-gallon bucket?

USU’s guidance is three 500 cc absorbers for a 5-gallon container. USU: “Oxygen will permeate plastic over a period of time,” so the bag inside the bucket is the barrier.

Can I store sugar or salt with oxygen absorbers?

USU’s sugar guidance: “Storage containers should be opaque, airtight, and moisture/ odor proof,” and “if sugar acquires a metallic flavor during storage, it should be discarded and replaced.” USU’s pages read for this audit (October 19, 2026) give no absorber guidance for sugar or salt.

Can I seal dehydrated or freeze-dried food I made at home?

USU’s requirement is “below 10% moisture content for storing with absorbers,” and its fact sheet lists dehydrated foods among those absorbers are used with. Home drying to a known moisture content follows the tested guidance in Food Preservation.

Do I need a vacuum sealer instead?

USU’s long-storage packaging for dry food is foil pouches, metal cans, PETE bottles or glass jars with oxygen absorbers; its statement on vacuum packaging is above (“NOT a food preservation method by itself”).

Where to go next

• Long-Term Food StorageWhat lasts, the conditions that decide shelf life, containers and pests.
• Home Food Store and RotationRotating stored food into everyday meals.
• Food PreservationDrying, freezing and canning with tested methods.
• Food PreparednessThe whole food system, layer by layer.

Sources

• Utah State University Extension: Oxygen Absorbers (Carolyn Washburn, fact sheet FN/Food Preservation/2011-01pr, October 2011) (read October 19, 2026). How absorbers work; below 10% moisture; botulism warning; sizes by container; 15-minute rule; storing unused absorbers; spent absorbers; foods absorbers do not improve.
• Utah State University Extension: Packaging Foods (read October 19, 2026). Mylar as a generic name; foil pouches as “exceptional food containers”; PETE bottles with absorbers; metal cans; vacuum packaging is not a preservation method by itself; rodents; sugar storage.
• Utah State University Extension: Storing Dry Beans (read October 19, 2026). Oxygen absorbers for dry beans; 10 or more years with oxygen removed.
• Utah State University Extension: Storing Wheat (read October 19, 2026). An oxygen-free atmosphere kills adult insects and prevents larvae from surviving; oxygen-free storage not necessary for wheat unless insects are present.
• Utah State University Extension: Storing White Rice (read October 19, 2026). Rice shelf life; “After opening use rice within one to two years.”
• CDC: About Botulism (last updated February 26, 2026; read October 19, 2026). Conditions in which spores grow and make toxin.
• Poison Help: The Poison Help Line (HRSA; read October 19, 2026). 1-800-222-1222; free and confidential.