What Foods Should You Never Store in Mylar Bags? (2026)

The short answer, sorted by reason

It helps to see the whole thing at once, because the reasons are different and only the moisture one is about safety. The question usually starts from a list of things someone already knows are fine:

I already have an/or already know to store Sugar, salt, flour, pasta, rice, beans, dehydrated milk, baking soda, baking powder, instant mashed potatoes, instant coffee, powdered creamer, coco powder, butter powder, and powdered peanut butter. Are there any other good things to store in mylar-bags?

That instinct is right, and the exceptions sort cleanly into four groups.

The one that is actually a safety issue

Start here, because the rest is money and this one is not. Sealing a food into Mylar with an oxygen absorber creates a low-oxygen environment, and low oxygen is precisely the condition Clostridium botulinum needs. If the food also carries enough available moisture, you have assembled the hazard rather than prevented it. That rules out fresh fruit and vegetables, raw or cooked meat, cheese, and any cooked dish, no matter how tightly you seal the bag.

Two things make that worse than it looks. Removing the oxygen also suppresses the ordinary spoilage organisms that would otherwise announce a problem by smelling bad, so unsafe food can look and smell perfectly fine. And the real line is not dry to the touch but water activity, the water actually available to microbes, below roughly 0.93 of which botulism cannot grow. That is why genuinely dry staples are safe and merely dry-feeling food is not.

The version that catches careful people is home-dried food, and it splits by acidity. Under-dried fruit is acidic enough that botulism is not the worry; mold and yeast are, and they will find it. Under-dried low-acid items, meaning vegetables, mushrooms, and any dried meat, are where the botulism risk actually sits. Jerky is worth naming outright: properly dried jerky keeps about two weeks at room temperature and then wants the fridge or freezer, so it is not a seal-it-for-a-decade food however leathery it feels. If you dehydrate, condition the food first and be certain it is crisp-dry, or use the freezer. Our shelf-life chart for dry staples covers which foods are reliably dry enough to begin with.

The oily foods: rancid with or without oxygen

This is the category that surprises people, because these foods are dry. Brown rice, nuts, whole-grain and nut flours, granola, and pet food all carry enough fat that they degrade from the fat itself. Removing oxygen genuinely slows oxidative rancidity, so it is worth doing, but fat also breaks down by enzyme and moisture routes an absorber cannot touch. You end up with a beautifully sealed bag of food that still tastes like old crayons in a few years. Owners who feed animals learn this early:

Don't long term store dog food, rotate it. Dog food goes rancid because of the fat content. Figure out how many buckets your dog eats a month, number the buckets, and rotate them.

It is a fair thing to be confused by, and one commenter asked the obvious follow-up:

I don't understand why dry dog food sealed without air would go bad because of fat, but other fatty foods, such as beef and cheese stored the same way wouldn't? I'm not disagreeing with you, I simply don't understand why this would be.

The answer is that fatty foods are not safe in there either; the difference is only in how they fail. Dry, fatty foods like kibble or brown rice will not grow bacteria, they will simply turn rancid and taste awful. Moist fatty foods like beef and cheese carry the actual pathogen risk. Neither belongs in decade-long Mylar storage. Seal the oily-but-dry group if you like, since it does buy time, but plan to rotate them in a few years rather than treating them as a 25-year staple, and use the freezer to stretch them further.

The ones that just do not need it

Salt and sugar do not spoil from oxygen, so an oxygen absorber does nothing for them but cost you a packet. They only need to be kept dry. You can still put them in Mylar if that is what you have, but a sealed bucket or any airtight container does the same job:

if you want to store anything that needs to be oxygen free, you need to use mylar bags. bucket lids arent air tight unless you buy gamma lids, they add up quick. salt ans sugar i imagine would be fine in buckets.

Worth flagging the nuance in that comment: a plain snap-lid bucket really is not airtight enough for foods that need an oxygen-free environment, which is the whole reason the Mylar liner exists. For salt and sugar specifically, though, it is fine, because they are not relying on oxygen removal in the first place. That distinction is covered in our bucket vs Mylar bag guide.

If a sealed bag puffs up, something is wrong

A working bag draws in and firms up, because the absorber is pulling out about a fifth of the gas inside it. So a bag that has inflated in storage is telling you something, and it is worth opening rather than ignoring. The usual causes are moisture that went in with the food, a seam that failed, or insect activity in the grain.

You will also read that baking powder in a premixed blend causes this by releasing gas. It is a tidy story that does not hold up, because chemical leaveners only react once they are wet, which is why baking powder kept dry for decades still works when it is finally used. Premixed baking blends are still worth splitting into their parts for storage, but for a duller reason: the fat in the mix sets its shelf life. Store plain flour, sugar, and salt separately and combine them when you bake.

What actually belongs in Mylar

The list of what works is long, and it covers the bulk of a real deep pantry. Dry, low-fat staples are what this method was built for: white rice, dried beans and lentils, wheat berries, pasta, rolled oats, plain white flour, degerminated cornmeal, and sugar if you skip the absorber. Owners packing serious quantities keep to that list:

I have bagged & bucketed various wheat (mostly Hard White Winter Wheat), rice, beans, soups, corn, powdered white & chocolate milk, drink mix, salt, sugar & other items.

You can also scale it down. Nothing requires a 5-gallon bucket, and smaller bags are the practical answer for things you use in modest amounts:

I’ve also used smaller sized Mylar bags for storing things I don’t need as big of quantities for: brown sugar, wheat flour, homemade apple chips. Same process but I skip the 5 gallon bucket.

Three notes on that. Brown sugar carries its own moisture and is a rotate-in-a-couple-of-years item rather than a seal-and-forget one. Dried milk is not a decades food either, ranging from a few months to a few years depending on how warm it is kept. And whole-grain cornmeal still holds its germ oil, which puts it in the oily group rather than this one. Temperature does quiet work in every figure here: the 25-to-30-year numbers assume a cool cupboard, and a hot garage cuts them closer to a decade.

So how do you decide?

Ask two questions about anything you are about to seal. Is it dry enough to sit on a shelf safely by itself? If not, no bag makes it shelf-stable, and the low-oxygen environment makes it worse rather than better. Is it oily? If so, the fat sets the shelf life no matter what you do about oxygen, so buy less and rotate it.

One last warning that has nothing to do with which food you picked: the absorber sachets themselves contain reduced iron and are a real poisoning risk if a child or a pet swallows one. Keep spares in a sealed jar out of reach, and never leave a sachet loose in food you are about to serve.

Pass both and you have a Mylar candidate, and the rest is mechanics: the right bag thickness and the right absorber size. Fail either and the honest answer is the freezer, the fridge, or a smaller bag you will actually finish.