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Food Storage FAQ

Comprehensive Food Storage FAQ v. 0.1.5

What is an Oxygen Absorber?
An oxygen absorber is a small packet of material used to prolong the shelf life of food. They are used in food packaging to prevent food colour change, to stop oils in foods from becoming rancid, and also retard the growth of oxygen-using aerobic microorganisms such as fungi.

The active ingredient is an iron oxide powder, which when it chemically reacts (ie. rusts) removes oxygen from the atmosphere.

How do I know when an oxygen absorber is working?
The most obvious sign an oxygen absorber is working is that it gets warm. When continuosly exposed to oxygen, some can get so hot as to be uncomfortable to touch, and will often form condensation on the inside of the outer package.

How do I know when an oxygen absorber is used up or no good?
This is one of the most frequently asked questions we get. The easiest way to tell if an oxygen absorber is good is to pinch the packet. If it feels ‘soft’ or powdery, the iron oxide powder is still in its original state and it is good. If it feels ‘hard’ or like a solid wafer in the packet, it is completely spent and should be replaced.

How long should it take for my absorber to remove all the air from my bag?
Some conditions are better than others for the speed at which an oxygen absorber works. For example, in a very dry climate, it might take up to a week for an absorber to fully activate. In a warm, humid climate it might take only 48 hours.

Why don’t some of your absorbers have the little pink pill in the pack?
This is another very common question. There are two main reasons. The first is it adds to the cost of the product. The second is that the pill doesn’t really tell you what you think it does. The pill (it’s official name is an Oxygen Indicator Tablet) only tells you that there is one good oxygen absorber in the pack, not that the entire pack is good. For example, if only 1 oxygen absorber in a pack is good and 49 are bad, the pill will still show pink. If the packets have been exposed to oxygen and 90% of their absorbing capacity is used up and only 10% remains, the pill will still show pink.

It is inifitely preferable that you use the ‘pinch method’ above to determine whether your absorbers are good, not an indicator tablet.

So what’s the history behind the pink pill?
The original seller of oxygen absorbers in the US for long-term food storage included these in the packaging. Interestingly, for them to get the pill into the packaging requires opening vacuum-sealed master bags, dropping in a pill, and resealing the pack. Thus, the factory-sealed packs we sell have been exposed to less air than the packs that have pills in them, making them more likely to be usable, not less.

How many oxygen absorbers should I use?
For 1-gallon bags, you should use 1-2 300cc oxygen absorbers. For 5-gallon bags you should use 5-7 300cc oxygen absorbers or 1 2000cc oxygen absorber. You should adjust this number up a little bit if you are storing less dense foods, such as pasta or some lentils, because the bags will contain more air even when full in comparison to very dense foods such as rice or wheat.

Do I need to use oxygen absorbers with everything I store?
Most foods will benefit in longevity when using oxygen absorbers. However, they are unnecessary when storing sugar or salt. In some cases, using an absorber with these foods will cause signficant clumping, although it won’t harm them otherwise. Also note that some foods may not store well for long periods of time no matter the method used (for example flour, yeast and some spices).

I ordered 20/50/100 Oxygen Absorbers, I’m definitely not going to use that many…what should I do with the rest?

The easiest way I’ve found to store oxygen absorbers is to use a small mason jar with a gasketed lid.  You’ll know you have a good seal because the absorbers will pull the pop-top down.  Try to use the smallest jar possible to minimize the work the absorbers you are storing need to do to clear the jar.  You can also re-vacuum seal the absorbers in their orginal or another oxygen barrier bag.

What is Mylar?
BoPET (Biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties and electrical insulation.

A variety of companies manufacture boPET and other polyester films under different brand names. In the US and Britain, the most well-known trade names are Mylar, Melinex and Hostaphan.

Wait, your Mylar bags aren’t clear; what’s up?
The polyester film is combined with a foil layer and in some cases another sealent layer of LLDPE (Linear Low-Density Polyethylene); this allows for good heat-sealing, UV protection, low odor transmission, and high puncture resistance.

How do I seal Mylar bags?
Please see this post and video about sealing Mylar bags. Mylar can be sealed with a variety of devices, including a hotjaw sealer, clothes iron, or hair straightener.

OMG, I can see pinholes of light coming through the Mylar bag, why is that?
All foil structure Mylar bags will have small pinholes in the foil layer. There is actually a measurement, ‘Pinholes per meter squared’, that is part of the specification of foil bags. Pinholes affect all foil structures, from a thin 2.5mil bag to the thickest 7-8 mil bags. The other transparent layers of the bag keep the integrity of these bags, and it is only very rarely (less than 1/100th of 1%) an actual ‘pinhole puncture’.

Why don’t my bags get hard when I use an oxygen absorber?
This is our third most common question. While there will be some compression of the Mylar bag after sealing due to the oxygen absorber, an absorber is only removing the 20% of the atmosphere in the bag that is oxygen, leaving the 80% that is nitrogen intact. Also, when sealing bags make sure you remove as much of the ‘headspace’ as you can; this is the area at the top of the bag you seal. Even a little headspace can use up much of the power of the oxygen absorber.

You Folded the Bags, eek!  Does folding hurt Mylar Bags?

The short answer is no, folding does not hurt Mylar bags.  The longer answer can be found here explaining why.

144 Comments Add Yours ↓

The upper is the most recent comment

  1. Tom #

    That definitely helps clear things up. Thanks!!

  2. Forrest #

    Just started using my mylar bags last week and they are working great. I have a question about putting spaghetti noddles in mylar bags them putting them in a plastic tote. The bag the spaghetti noodles in is not shrink up at all but I do not feel air in the bag, more like space. But, the other pasta I’ve stored in mylar like larger noodles has really shrunk up well with no room at all. I’m wondering if I’m trying to put too much in the bags. How do you know how full to fill the mylar bag. The bags seem to do better when you just have enough room on the top to seal them shut. My sugar and flour are also doing the same thing, I don’t feel air in the bag but they are not shrinking like the others are. Is that normal? Thanks again for all your help.

  3. Forrest #

    Can I fill mylar bags with different items like beans, flour, pasta, spices, etc and put each bag in a 5 gallon food storage bucket? Do I need to use a mylar bag for the 5 gallon bucket if the bags I’m putting inside the bucket are already in mylar and sealed? I would think that if the bags are sealed the purpose for putting them into a clean bucket would be just to keep the bugs and critters out. Please corrent me if I am doing this wrong.

  4. 4

    Hey there! A couple of notes…don’t use an oxygen absorber with sugar, it will clump together badly over time (still edible, it will just be hard to work with). Sugar and salt are 2 items that will store indefinitely without any special help.

    If you are using the lighter bags, it is possible that the spaghetti is puncturing the bag. We recommend a 4.5mil and up for ‘pokey’ foods like that. Alternately, you can wrap the top part with a plastic bag, wax paper, or something similar to keep the sharp edges from contacting the bag.

    You are correct, the bags will contract more if full, to an extent. Some foods, such as the flour, potato flakes, mixes, and others may not shrink at all…flour, for example, because it is almost a ‘solid’ when compacted, there is very little air to remove to cause a vacuum-like effect.

    In many cases, you can have food that is stored properly that will not draw down, due to the above factor, or having just a touch too much air in the package when starting (headspace). The oxygen will still be removed, but because nitrogen makes up 80% of air and will always remain in your bag, sometimes when the 20% of oxygen is removed, it will still feel like there is air in the bag.

    To your 2nd comment, sure, there is almost no wrong way to store your food if using buckets, and their main benefit is exactly as you said, to prevent critters from getting to it. Many folks make their own ‘Superpails’ by adding a variety of food to each bucket, so if they open one, they can make a wider variety of items. No, you don’t need to use a 2nd larger Mylar bag in a 5 gallon bucket. You can usually fit 4 1 gallon bags into a 5 gallon bucket. You’ll have some space left over, and using even smaller bags with spices or flavorings (e.g. powdered cheese for mac and cheese) can help you maximize your space.

    I hope that helps!

    Thank you!

  5. Marnie #

    I ordered the 5 gallon Ziplock zip seal mylar bags. I want to store 4 pound bags of dry cat food. Is it best to put the bags inside the mylar bag in the 5 gallon bucket and add the appropriate number of oxygen absorbers before sealing the mylar bag? OR should the cat food bags be opened and poured directly into the mylar bag with oxygen absorbers? Just don’t want the cat food to get ‘buggy’.

    ALSO, can small bags of rice be sealed and successfully stored in these large ziplock mylar bags with the oxygen absorber and then into the 5 gallon bucket?
    OR, should I purchase smaller mylar bags and transfer the rice into them before storing?

    THANKS . . .

  6. 6


    Thanks for the questions! I recommend removing food from their original packaging, so yes, I’d pour the bags into the Mylar first. It is one less item to worry about in the process, which is always good. Check out the ingredient list of the cat food before you determine how long you’d like to store it; many healthy pet foods have high oil/fat content, which can cause them to spoil. You should probably get a couple of years out of it, but I always recommend pet food be rotated just like people food. For rice, especially if you cook with it often like we do in our house, having it in 1 gallon bags is definitely more convenient. When I first started prepping, I put a bunch in 5 gallon buckets before I realized we needed to actually use it regularly.=) Now we store the foods we use most in 1 gallon bags and buckets.

    As a side note, for best long-term results with the Zip Seals, we still recommend sealing above the Zip portion. The tear notch allows you to still have the protection of the Zip seal after opening it the first time.

    Thank you!

  7. leslie #

    Hi…I just received all my heirloom seeds and the mylar bags….can i put the little packs of seeds in a mylar bag and seal with my food saver?

  8. Hol #


    Just got sone Mylar bags and o2 absorbers and was going to do usual flour, oats, pasta minus the egg, dried pinto beans and white rice. I was wondering if you suggest cornmeal, baking powder and soda, and spices. I am looking to store them for as long as possible and not used them for emergency purposes and am not sure if the items above are ok to store in Mylar bags with o2 absorbers what spices do you suggest that will keep vertually forever? Is there any special requirements for dried cheese and milk? Thank you

  9. 9


    Heya, thanks for the question. I’m not a seed expert, but I know a lot of folks who seal seeds in Mylar. My concern is do seeds need to ‘breathe’? Meaning if you remove all the oxygen, can you ‘kill’ a seed? I’ve seen conflicting answers on the subject, and I just don’t know enough to answer the question. I will do some research this week and see what I can find!

    Thank you!

  10. 10


    Good questions. Watch out for oils/fats in your cornmeal and other baking mixes, as those will spoil more quickly. Consider storing dent corn and investing in a good grinder (you’ll need a special bit for grinding corn) making your own. Baking soda stored well will last indefinitely…add a couple of drops of vinegar to a bit of baking soda, and if it bubbles, it is still good. A 2 to 1 ratio of Cream of Tartar and Baking Soda mixed thoroughly will make Baking Powder. Your best bet is to store the components and only mix when you need to, as you’ll likely get 18 months tops from stored baking powder.

    For spices, the answer is ‘it depends’. Root spices can last a very long time, and salt is the best store-able spice as it essentially has a shelf life of forever. A good rule of thumb is you can use your spices as long as they look and smell good; however, you may just have to add more than a recipe calls for. For example, if your Garlic powder isn’t working up to standard, use 2 teaspoons instead of 1 and see if it provides the taste you are used to.

    The ‘use by’ date on many spices is far less than you will actually get from them. We have spices that have followed us for multiple moves and many years that still taste fine, many years after their dates say we should have discarded them. As long as you keep them dry, you can use most spices indefinitely. Keep in mind I have a poor palate, so I wouldn’t be able to taste the difference between strong sage and weak sage.=)

    Good luck!

    Thank you!

  11. Tom #

    If I use an iron to seal my mylar bags what heat temprature should the iron be set to. I also have a hand held bag sealer when sealing up chip and etc. It seems to do a good job, would it work on the mylar bags a well?

  12. 12


    Heya, thanks for the question. Most times, you should set the iron to the Wool setting. Sometimes an iron will run a little cooler or hotter, and you might have to adjust it slightly.


  13. 13

    can i use a vaccum sealer to seal the bags

  14. 14

    do i use mylar bags when storing baged noods and spagett, how about pagage pototoed, and rice.they come pagage from the store in foil.can i just put them in a bucket and seal it with an oxgen, or shough they go into a mylar bag first.

  15. Ron M #

    I want to vacuum seal and freeze jerky. Is it OK to use the absorbers along with freezing. I have problems with the jerky puncturing the bags when I vacuum seal all the way. I thought I might leave a little air in and remove the rest with the absorbers then freeze. Do you think this would work? If so how long before I can put the absorber in the freezer?

  16. 16


    Heya, sorry for the slow response, it’s been crazy! You can use some vacuum sealer’s to seal the bags, though we don’t recommend using the vacuum function. It’s easiest if the bag is not as wide as the vacuum sealer, though with some you can seal part of the bag and then the rest with a 2nd seal.

    Hope that helps!

    Thank you!

  17. 17

    Charlene, thanks for the question! I recommend removing food from its original packaging. Though with some pasta’s like spaghetti, you’ll want to wrap the ends with saran wrap or something similar to prevent it from puncturing your bag.

    Thank you!

  18. 18

    Ron, if your jerky is puncturing your bags, try wrapping it in saran wrap or wax paper prior to vacuuming. In general, you only need to either vacuum seal or use an oxygen absorber. Oxygen absorbers remove oxygen down to about .1% vs about 2% for vacuum sealing, but if you are putting it in the freezer, the difference in results between the two will be minimal. At shelf temperatures, I would definitely use 02 absorbers as many manufacturers do, to extend its shelf life.


  19. Forrest #

    How about taking store bought cereal like frosted flakes, etc out of the box and storing it in mylar bags for long term food storage? Any idea on what the shelf life of that would be like, or would it be just a waste of mylar bags and absorbers?

  20. Forrest #

    I saw that one well know food storage supply is selling #10 cans of brown sugar and cornmeal online with a shelf life of 5 yrs. From my understanding you cannot store either one if these items long term. If this is the case, can I store cornmeal and brown sugar in mylar bags and get the same shelf life as they are claiming with using the #10 cans? If not, how long will cornmeal and brown sugar keep in mylar? Thanks

  21. Celia #

    If I have put oxygen absorber in the mylar bag and placed it in a 5 gal bucket that has a really tight seal. I did not seal the mylar bag, I just folded over the top and now I am told that I need to. Is that so? And, if I open them to seal the bag, will I need to put in a new oxygen absorber or will the old one still be good?

  22. 22


    You can get decent results from cereal, though you want to store on a dry day, as moisture is the big killer of most cereals. As most cereals have a ‘best buy’ date and not an expiration date, you can get at least double, and potentially much longer, from them (so if you buy them in the store with a 6 month shelf life, you can get at least a year from them). I have Wheaties in their original packaging a year past their ‘best buy’ date (18-24 months from purchase date) and while they are not as obviously fresh as in-date cereal, they are definitely edible.

    I hope that helps!

    Thank you!

  23. 23

    Looking at a Brown Sugar Manufacturer website, it looks like you can get 5 years from brown sugar, and potentially longer as they say storage is indefinite. Based on their requirements, Mylar will work fine: “Air hardens brown sugar. Store it in a cool, moist area in a covered container. If that’s not possible, store the entire container in a second canister with a tight-fitting lid. You can also empty the sugar into a rustproof container (or a heavy, moisture-proof plastic bag) and keep it tightly closed.”

    Corn meal without the germ can be stored long term, it’s like the difference between brown rice (6 months) and white rice (a loooong time!). Check the packaging, if there are fats or germ present, I wouldn’t rely on it long term or try to store it much past the expiration date. And always give everything a good sniff when pulling out of storage, and never eat anything that smells ‘off’.

    In general, if a food storage company is saying something will last ‘X years’, they probably have the research to back it up, as food-based liability is a killer, and is one of the reasons we have stayed out of the actual food arena.

    And sorry about the slow response, been a crazy week!

    Thank you!

  24. 24


    Thanks for the excellent question. The best way to think of storing your food is that the bucket is only there to protect the Mylar bag from punctures and pests. It is not oxygen impermeable, meaning oxygen will seep in over time, even if the seal is perfect (the plastic ‘breathes’). You should heat seal your Mylar with absorber inside to long term store your food. Yes, you will likely need to use a new absorber in this case, more as a precaution than anything else. I’ve had punctured Mylar bags that still leaked so slowly that the absorber was still good a month later, but its best not to take chances with your food!

    Thank you!

  25. Forrest #

    Thanks for the advice. Can I get longer shelf life by storing store bought beef jerky in Mylar with oxygen absorbers? If so, how long of a shelf life will it have? Also I want to store wheat in Mylar or buckets but I cannot find anywhere in Denver,CO to buy it. Any ideas. Thanks again.

  26. Forrest #

    I bought a dehydrator and I’m starting out drying strawberries. I’ve read online that they will store 1 year in mason jars. I want them to store longer. I tried to find something about shelf life of fruits that you dry at home and then store in mylar with oxygen absorbers, but I’m getting a lot of mixed thinking on that. If dehydrated properly down to a crisp, how long can I store them in mylar bags with absorbers? I know emregency stores say a 30 year shelf life but if I dry my own can I get the same shelf life? Thanks.

  27. 27

    i would like to know a couple of things. (1) when you have boxed stuff like old grotten potwtoes, shought they be taken out of there bags and boxs to be put in mylar bags. (@)what about dry beans do theye need to be open from there bags to mylar bags. (3) can you put noodles in zipped locked bags then put them into mylar bags. i cant aford mri food, so have to go with what i can get from stores. i dont have a basement i do have a barn its hot and cold can you tell me whats the best way to keep food the longest. thank you, charlene

  28. 28

    i would like to know if we have preppers in hyland ct.,or adams county ohio. would like to know. please if there is someone who is close please e-mail me thanks everyone.

  29. 29


    Thanks for the questions. I recommend removing foods from their original packaging; it would probably be alright either way, but I prefer to remove the chance of microbial growth, especially in ‘paperish’ type packaging that flour or sugar might come in. You can put noodles in plastic bags, and I recommend it for pasta like spaghetti to prevent it from puncturing your Mylar Bag. Fluctuating temperatures can be a killer to a food’s shelf life. If there is any way to keep it indoors or in a root cellar or similar, that is your best bet. Many folks store foods in totes under beds or in closets. In the closets case, be wary, because often they don’t benefit from heating/cooling of the rest of your house, and can get very hot in the summer. I notice our cupboards can be 15 degrees warmer than much of the house at times of the year.

    Thank you!

  30. 30

    Good questions. The 30 year shelf life is for freeze dried fruits; dehydrating won’t get them anywhere near that. I would look into syrups like they use for pears or peaches, as it is a sugar-based preservative and should allow you to keep your fruits storable for far longer. There were some interesting finds recently of foods canned this way from over 100 years ago still being edible (though I don’t recommend trying to store them that long!).


  31. 31

    I don’t recommend trying to store store-bought jerky with Mylar. Many have a high moisture content and simply won’t get much benefit from it. You always want to find foods with as low a moisture content as possible. Check into canning meats for protein; it is a pretty simple process and is better for your stores than almost anything you can buy. I think I should do a canning meat post, as it is something I would like my wife and I to get into this summer!

    Thank you!

  32. Tommy #

    Can I cut down the size of the bags ?

    I’m sure the answer is obvious, will all edges seal evenly?

  33. 33


    Thanks for the good question! Yes, Mylar can be cut down to any size and resealed along all edges. It may take some time to figure out the best seal thicknesses to ensure no leaks, but many folks cut down the 5 gallon bags to 1/4 or 1/2 of the size to use for smaller portions.

    Thank you!

  34. K,D #

    Do you Have a List of What you Can use the oxygen absoers on like the top 25 food. i have bags 1GL bags and how meny Ox,ab do you need and can you use to meny on something.

  35. 35

    Thanks for the questions! First, use 1-2 300cc absorbers per 1 gallon bag. No, you can’t use too many; the absorbers will just stop working once they’ve absorbed all the oxygen. Some folks use 300cc absorbers in quart mason jars so they can open and close the jar several times before having to replace the absorber.

    The best foods to store are those with a moisture content below 10%, and includes mostly dry staples: rice, beans, wheat, legumes, lentils, other grains, and pasta. If you store these, also make sure you have sufficient water and cooking supplies (baking powder and soda, yeast if you want rising bread, salt, sugar (do not use oxygen absorbers with either salt or sugar), oil, etc.

    I hope that helps!

    Thank you!

  36. SH #

    I previously purchased Hot Hands hand warmers as I was told these are oxygen absorbers. They don’t say how many cc’s they are tho. Is 1 enough for a 5 gal bucket?

  37. SH #

    In the question above about what Mylar is, you said that it is an elctrical insulator. My question is, could you put your cell phones and such in a Mylar bag and put it in a metal trash can, or something similar, and have a Faraday Cage?

  38. 38


    Some people do, but because I haven’t tested it, I can’t verify it would perform like a Faraday cage. While the food storage Mylar bags do have some electrical insulation properties, I would likely use the brown Mylar that electronics sometimes ship in as a more likely candidate, as its electrical protection properties are much higher!


  39. 39


    Good question. They work on the same principle, but I’m wary of using Hand Warmers as oxygen absorbers. First, they are not FDA approved for contact with food, and I also don’t know what their CC rating would be (or even if it would be consistent warmer to warmer). I would definitely test them, starting with a 1 gallon bag and working your way up, before actually using them in real food storage.

    Thank you!

  40. K.D #

    ? on Flour can you use oxygen absoers with Flour

  41. 41


    Sure thing, though we recommend rotating your flour first in first out. Be careful when packing flour as well, because it is very fine and can easily clog up your seal.

    Thank you!

  42. Dee Dee Hudson #

    If we store something like Corn Flakes or crackers, will the “sucking out” of the air crush the contents to crumbs?

  43. 43


    Sorry about the slow reply, I missed your note the first time through! Yes, if you pack the bag too tight with crunchables, they will sometimes crush when using oxygen absorbers. There is a magic amount that will let the air get removed but not destroy the contents; it will just take a couple bags to figure out where the sweet spot it.

    Hope that helps!

    Thank you!

  44. KD #

    Can Oxygen Absorbers Be use on Cornbread mixs or cakes mixs? and Baking Soda or popcorn. thanks

  45. 45

    You can use them; however, if there are oils present in the mixes it won’t keep them good much longer. I’d simply make some cakes every 6 months or a year and rotate them out!=) You can use absorbers for popcorn as well, but not necessary for baking soda.


  46. jeremy #

    What is the shelf life of storing Masa or corn flower? And you said that white rice has a looong shelf life if stored correctly? Does this pertain differently to long grain or short (basmati) grain varities? Also what is the storage time for powdered fats ie dried milk and powdered cheese? Thanks!

  47. suzie #

    I want to vacum pack using pint size bags. What size oxygen absorber do I use? I was thinking about 1 200cc. Am I correct?

  48. 48

    Aloha. So often when I read about food storage there are comments like “Do it on a dry day”, “store in basement” or “store in a cool dry place”. Simply put, none of that is going to happen in Hawai’i. Unless you’re got extra funds and have a dehumidifier, air conditioner, solar set up in a well-sealed home – but the majority of us are in consistant humid 80degrees. I do have a outdoor Matson for extra storage. And it gets muggy and moist in there – but there are no options. So basically what I’m getting at is: Tropical Prepper (on a budget) tips please! Hey, perhaps you help me do a (guest)piece for my web site??? Mahalo!

  49. Dianna #

    I am curios as to the diameter of the pails? Would the gamma lids fit the smaller buckets?

    About how much food can you store in the 2 smaller containers? I buy various bulk items that we use daily and this would make using them so much easier.

  50. mccoy2708 #

    Are there guidelines to use whether to store/seal your food by vacuum sealing or mylar and O2 absorber? Also, I have seen several places where you suggest not using vacuum with mylar at all, why not? I am just getting a serious start after thinking/discussing food storage with my family for a while, and want to get the most out of my efforts. thanks

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