Where Shelf-Life Numbers Come From: A Sourced Storage Table
Figures last verified
Search for how long flour lasts in mylar and you will get 10 years, 15 years, and 25 years from three different pages, all stated with equal confidence and none of them citing anything. The pages are almost universally published by companies that sell mylar bags, oxygen absorbers, or packaged food storage, and the numbers drift upward accordingly.
This table gives the figure, where it came from, what storage conditions it assumes, and whether it rests on measurement or extrapolation. Where sources disagree, both numbers appear rather than an average.
Why the numbers disagree
Four things explain nearly all the variation between charts.
Shelf life means different things. A food can be safe to eat, nutritionally intact, or palatable, and these expire in that order from longest to shortest. Wheat sealed properly is safe essentially indefinitely, loses vitamin content over decades, and can become unpleasant long before it becomes unsafe. A chart quoting 30 years and one quoting 10 may both be right about different questions.
Fat content governs almost everything. Fats oxidize and go rancid, and oxidation is what oxygen absorbers slow rather than stop, since some oxygen remains dissolved in the food itself. This is why white rice and brown rice differ by an order of magnitude despite being the same grain: the bran contains oil. Whole wheat flour and white flour split the same way.
Storage temperature moves the answer more than packaging does. A widely used rule of thumb in food science holds that reaction rates roughly double for every 10 degrees Celsius increase, which means the same sealed bucket lasts several times longer in a 55F basement than in a 90F garage. Charts rarely state the temperature they assume, and most implicitly assume a cool basement.
Testing versus extrapolation is the last one. Very few of these figures come from someone opening a container after 25 years. Most are accelerated-aging estimates or institutional experience, and the honest ones say so.
The table
The conditions column assumes sealed mylar with an appropriate oxygen absorber inside a food-grade bucket, stored dark, unless stated otherwise.
| Food | Commonly published | More conservative figure | Basis |
|---|---|---|---|
| Hard red or white wheat, whole berries | 30+ years | 25 years | Long-institutional experience; among the best-documented staples |
| White rice | 25 to 30 years | 20 years | Long-institutional experience |
| Brown rice | 6 months to 1 year | 1 to 2 years sealed and cool | Bran oil oxidizes; freezer storage extends substantially |
| Rolled oats | 25 to 30 years | 20 years | Institutional; fat content is low but not zero |
| Dry beans, all types | 25 to 30 years | 10 years for palatability | Safe far longer than they are pleasant; older beans resist softening and may need pressure cooking |
| White flour | 10 to 15 years | 10 years | Milled surface area accelerates staling and oxidation versus whole berries |
| Whole wheat flour | 1 to 2 years | 5 to 10 years sealed and cool | Widest disagreement of any item on this table |
| Pasta | 25 to 30 years | 20 years | Low fat, low moisture |
| Cornmeal | 10 to 15 years | 5 to 10 years | Germ oil content varies by degermination |
| Sugar, white granulated | Indefinite | Indefinite | Does not support microbial growth; hardening is a texture issue, not spoilage |
| Salt | Indefinite | Indefinite | Mineral, not organic |
| Honey | Indefinite | Indefinite | Crystallization reverses with gentle warming |
| Powdered milk, nonfat | 20 to 25 years | 10 to 15 years | Residual fat and lactose browning limit palatability |
| Powdered milk, whole | 3 to 5 years | 2 to 3 years | Fat content is the constraint |
| Powdered eggs | 5 to 10 years | 5 years | Fat and protein both degrade |
| Freeze-dried fruit and vegetables | 25 to 30 years | 20 years | Commercially packaged in cans with absorbers |
| Dehydrated vegetables | 8 to 10 years | 5 to 8 years | Higher residual moisture than freeze-dried |
| Textured vegetable protein | 10 to 15 years | 10 years | Defatted soy; low fat is the reason for the long figure |
| Instant potato flakes | 20 to 30 years | 15 years | Institutional |
| Cooking oil, sealed | 1 to 2 years | 1 year | Not a long-term storage item under any packaging |
| Nuts and seeds | 1 to 2 years | 1 year, or frozen | High fat; do not belong in long-term buckets |
| Coffee, whole bean | 2 to 3 years | 1 to 2 years | Oils and volatile aromatics both degrade |
Foods that should not go in long-term storage at all
Anything with meaningful fat content will go rancid before the packaging fails, and no amount of mylar changes that. Cooking oil, nuts, seeds, whole-grain flours in quantity, whole milk powder, and jerky all belong in a rotating one-to-two-year supply rather than a 25-year bucket.
Anything above roughly 10 percent moisture is a botulism risk in an oxygen-free environment. This is the reason oxygen absorbers must never be used with high-moisture foods. Clostridium botulinum is an anaerobe, and removing oxygen from a moist food creates conditions that favor it. Dry goods below 10 percent moisture do not support it, which is why the technique is safe for grains and beans specifically.
Home-dehydrated foods are the practical trap here, because home dehydration rarely achieves the residual moisture levels commercial freeze-drying does, and the difference is invisible. The USDA's food safety guidance is the appropriate authority on moisture thresholds rather than any preparedness site, this one included.
What the figures assume about your storage
Every number above assumes a stable cool temperature, darkness, and an intact seal.
Temperature is the variable most within your control and the one most often ignored. A garage in a hot climate can average 30 degrees Fahrenheit above a basement across a year, which plausibly cuts these figures by half or more. If the only available space is warm, the honest planning move is to halve the table rather than to buy thicker bags.
Darkness matters because light drives oxidation and degrades vitamins. Mylar is opaque, which handles this, but clear PETE containers and glass do not.
Humidity matters mostly at the seal. A humid environment does not penetrate an intact mylar seal, but it does corrode bucket lid gaskets over time and it makes any pinhole failure worse.
Rodents defeat all of it. Mylar is not a rodent barrier, which is the entire reason buckets exist, covered in food-grade buckets, gamma lids, and what actually seals.
How to read any other chart you find
Three questions expose most of them.
Who published it, and do they sell storage supplies. This is not disqualifying, since the vendors genuinely have the most hands-on experience, but a 30-year figure from a bag seller and a 30-year figure from an extension service carry different weight.
Does it state storage temperature. A chart with no temperature assumption is quoting a best case.
Does it distinguish safe from palatable. Charts that give a single number are almost always quoting safety, which is the least useful of the three thresholds for someone deciding what to buy.
University extension services are the most reliable free source in this space, since they publish USDA-derived guidance without a product to sell. Utah State and Brigham Young have both done substantive work on home food storage specifically, including packaging integrity testing, and their materials are worth reading directly rather than through a reseller's summary.
Using this in practice
Store what stores well and eat the rest on a rotation. The top of this table, meaning wheat berries, white rice, beans, pasta, sugar, and salt, covers the overwhelming majority of long-term calories at the longest shelf lives and the lowest cost per calorie, which is worked out in what emergency food actually costs per calorie.
Store grain rather than flour where possible. Whole berries outlast flour by a factor of two to three, and the mill is a one-time purchase.
Date every container with the pack date rather than a projected expiry, because the projection depends on where it ends up sitting and the pack date does not change.
Packaging method determines whether these figures apply at all, and the components are covered in oxygen absorber sizing, mylar thickness, and insect pretreatment.