Skill guide · Water & Food

Sealing Bulk Food for Long-Term Storage

The Water & Food chapter's Tier 2 goal is bulk staples stored in Mylar with oxygen absorbers, in one line, with no actual technique behind it. Buying the bags and the food is the easy part; sealing them correctly is what determines whether that stockpile is still good in five years or has gone stale, buggy, or rancid in one.

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What this method is for

Mylar-and-oxygen-absorber storage works by blocking light, moisture, and oxygen, the three things that degrade stored food fastest. It's built for dry, low-moisture, low-fat staples: white rice, dry beans and lentils, oats, pasta, wheat berries, dry corn, sugar, and some dehydrated vegetables. Done correctly, these can stay good for well over a decade.

This isn't the right method for everything

Fats and oils go rancid from oxidation and heat regardless of how well you seal them, an oxygen absorber slows that but doesn't stop it, so treat high-fat foods (nuts, whole-grain flour, anything with real oil content) as a shorter-rotation item, not a decade-plus stockpile, no matter how they're packaged.

Warning

Never use this method on anything above about 10% moisture, that's a real botulism risk, not just a spoilage one

An oxygen absorber creates exactly the low-oxygen environment Clostridium botulinum, the bacteria behind botulism, needs to grow, the same organism Food Preservation centers its entire canning safety case around. Dry staples like rice, beans, and pasta are safe because they're dry enough that nothing can grow regardless of oxygen level; anything with meaningfully more moisture than that turns the same sealed bag into the exact anaerobic environment the bacteria favors. That specifically rules out home-dehydrated fruit, vegetables, and jerky unless it's verified fully dry (commercial freeze-dried food is a different, genuinely low-moisture product and is fine), brown rice (its bran layer's oil content is a rancidity problem on top of the moisture one), and anything with visible moisture or a soft, pliable texture rather than a hard, brittle one. When genuinely unsure whether something is dry enough, don't seal it this way.

How long will it actually last your household

Before sealing anything, it's worth checking whether what you've bought actually covers your household. The worksheet below uses a flat 2,000 kcal per person per day as a simple, conservative floor, not a personalized target: see Calorie Planning for Your Food Supply for the real activity-tiered numbers (1,800 sedentary, 2,200 moderately active, 2,600 active), nothing here contradicts that guide. Use 2,000 for a quick sanity check, then swap in the tier that actually matches your household, especially anyone doing hard physical labor, before treating the result as a real plan. Add up the calories in what you've stored, nutrition labels list servings per container and calories per serving, then divide by the household's daily need.

Fill in your own numbers. Each line combines with the one above it; a rule marks a line that's an answer rather than another number to add in.

people in the household

× kcal calories per person, per day (2,000 is a conservative floor, see Calorie Planning for tiered numbers)

= kcal/day daily need

kcal total calories stored (servings per container × calories per serving, added up)

÷ kcal/day daily need, from above

= days days covered

Worked example: a household of 4 at the 2,000 kcal/person/day floor needs 4 × 2,000 = 8,000 kcal/day. A stock totaling 168,000 kcal covers 168,000 ÷ 8,000 = 21 days.

Enter your own numbers below to run the same math instantly.

People in the household Calories per person, per day 2,000 is a conservative floor, not a personalized target; see Calorie Planning for Your Food Supply for activity-tiered numbers (1,800 sedentary, 2,200 moderately active, 2,600 active). Raise it for children, larger adults, pregnancy, or hard physical labor. Total calories stored Servings per container × calories per serving, added up across everything you're counting toward this supply.

Pet food isn't counted here

There's no sourced daily-calorie figure for pets on this site the way there is for people, feeding needs vary too much by species, size, and the specific food. Pet food is sized differently in practice anyway: check the feeding guidelines printed on the bag for your pet's weight, multiply by however many days you're planning for, and store that separately from the household's own calorie count above.

Materials

Item	Spec	Notes
Mylar bags	5–7 mil thick, food-grade, sized to your storage plan	Thickness is what actually blocks oxygen over years, not just at sealing time; 5 mil balances flexibility and durability for most staples, 7 mil for sharp-edged foods like pasta or hard beans. Gallon bags for smaller portions, 5-gallon bags to match a matching bucket
Oxygen absorbers	300cc per gallon of bag volume as a baseline	Round up rather than down; an absorber slightly too large does no harm, one too small won't fully displace the oxygen
Heat source	A dedicated impulse bag sealer, or a clothes iron/hair straightener set to a cotton or wool setting (roughly 380°F) with steam turned off	An impulse sealer applies heat in a thin, consistent line in 2–3 seconds and is the more forgiving choice for a first attempt; an iron or straightener spreads heat over a wider area and has to be dragged evenly by hand, which is where most beginner seal failures happen
A flat board or ruler	Anything rigid, a foot or so long	Slides inside the bag under the fold to give the heat source a firm, flat surface to press against; sealing without this backing is a common cause of wrinkled, leaky seams
Outer container (optional)	A food-grade 5-gallon bucket	Protects the Mylar bag itself from punctures and pests once sealed. One 5-gallon Mylar bag holds roughly 30–40 lbs of dry rice, wheat, or beans; four 1-gallon bags fit inside one 5-gallon bucket instead if smaller portions are the goal

Sizing the oxygen absorber

Bag size	Oxygen absorber
1 quart / small bag	About 100–300cc
1 gallon	300–500cc
5 gallon	2,000–3,000cc

When in doubt, size up rather than down. An oversized absorber just finishes its job faster; an undersized one leaves residual oxygen in the bag, which defeats the point.

Step by step

Have everything ready before you open a single oxygen absorber packet: bags filled and staged, sealing tool warmed up if needed, an impulse sealer typically takes 10–30 seconds and signals ready with a light, while an iron or straightener needs a few minutes to reach its target temperature. This matters because of the next step.
Work fast once an absorber packet is open. Oxygen absorbers start reacting with air the moment they're exposed to it, not just the air trapped in your bag. Get each one sealed into its bag within about 15–20 minutes of opening the packet, or its capacity is wasted absorbing room air instead of the air in your food.
Fill the bag with food, leaving about 3 to 4 inches of empty bag above the contents, enough to fold and work with but not so much that you're sealing mostly air.
Drop the oxygen absorber in on top of the food, don't set it aside "for a minute", every minute it sits in open air is capacity lost.
Press out as much air as you reasonably can by hand. A true vacuum isn't necessary, the absorber handles what's left.
Fold the top of the bag over on itself two or three times to create a flat sealing surface, then slide a flat board or ruler inside the fold as a firm backing and smooth the Mylar taut with both hands to work out wrinkles before sealing; wrinkles left in the fold are the most common path a slow leak takes.
Run your heat source across the fold with firm, even pressure for about 3–4 seconds, in one smooth pass across the full width of the bag.
Check the seal immediately by gently trying to pull the fold apart. If it separates at all, reseal that section.

Confirming it actually worked

Check every bag again within 24 hours of sealing. A properly sealed bag with a correctly sized oxygen absorber will be noticeably vacuum-tight, the Mylar pulled snug against the food inside, since the absorber has consumed the oxygen that was left in the bag. Keep in mind oxygen is only about 21% of air, so even a perfect seal won't pull down to a hard vacuum, snug and wrinkle-free against the food is the real target, not rigid. Look closely along the seal line itself for any wrinkle or gap, that's the specific spot a slow leak comes from even when the rest of the bag looks fine. If a bag still looks puffy or loose after 24 hours, the seal likely failed somewhere; open it, replace the oxygen absorber with a fresh one, and reseal.

Storage and rotation

Label every bag with the contents and the seal date, the same FIFO habit used everywhere else on this site.
Keep sealed bags somewhere in the 50–65°F range with humidity under 60%, a basement or interior closet rather than a garage or attic that swings with the outdoor temperature. Every 10°F cooler roughly doubles expected shelf life, so where a sealed bag sits matters almost as much as how it was sealed.
Store sealed bags inside a food-grade bucket where practical; the bucket protects the Mylar itself from punctures, rodents, and crushing.
Check seals seasonally, and watch for small holes or frass (insect droppings) in grain and bean stores, exactly the inspection routine already called for in the Water & Food chapter's Tier 2 rotation guidance.
Once a bag is opened, its long-term protection is gone; move the remaining contents to a shorter-rotation container rather than resealing the original bag and expecting the same shelf life.

Sources

Utah State University Extension, food storage guidance for Mylar-packaged staples: USU Extension
Oxygen absorber sizing per bag volume, activation timing, and seal verification technique: Oxygen Absorbers; Discount Mylar Bags
Mylar bag mil thickness for long-term storage: Brand My Dispo
Heat sealer temperature settings and iron/straightener technique: TruePrepper
Fold-backing and wrinkle-free sealing technique: BNPack
Seal troubleshooting and common leak points: Cubit Packaging
Bucket-and-bag food quantity yields: PailHQ
Storage temperature and humidity effect on shelf life: Mother Earth News
Botulism risk above 10% moisture content in oxygen-absorbed storage, and foods unsafe for this method (home-dehydrated fruit/vegetables/jerky, brown rice): Primal Survivor; KMJbag