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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. 1

    Heya, thanks for the question! I recommend absorbers over vacuum sealing simply because they are more effective. A vacuum sealer can remove down to about 2% oxygen remaining in a bag, where oxygen absorbers remove down to .1%, or a factor of 20 better. Vacuum sealing is still a good process, but if you want the longest possible shelf life, oxygen absorbers are the way to go.

    Thank you!

  2. 2


    Hey there! Pail diameter is generally 12″ for a 5 gallon (and 6) bucket. The smaller buckets will not work with the Gamma Lids. The 1 gallon buckets can store about 10 lbs, and the 2 gallons about 18-20lbs.

    Thank you!

  3. 3


    Generally, my rule is, ‘do what you can.’ If you can’t fit all the ‘best’ criteria, then meet as many as you can. Hawaii is beautiful, but definitely a challenge for storing food due to the climate! I’ll see what I can work up in the way of some tips for more tropical climates!

    Thank you!

  4. 4

    For a pint size, 200cc will work and will likely be a little overkill (never a bad thing!!). 100cc will work as well!

    Thank you!

  5. Mike #

    I know that storing flour long term is not recommended. But if a person was going to do it what would be the best way? to leave the flour in the paper bag and put that inside the myler with an oxygen absorber between the pAper and mylar then in a 5 gallon pail… or to dump the flour into the mylar with the oxygen absorber directly in the flour and then put it in a 5 gallon pail? .. Also same question for rice in plastic bags Thanks-Mike

  6. Marta #

    Hello, I have a Professional III Foodsaver brand vacuum sealer. Will your mylar bags works with that product?

  7. K D #

    can you use o2 absorbers with Quaker oats oatmeal ?

  8. Forrest Kuczmarski #

    I’ve seen on Youtube folk’s who are taking Pasta Sides pouches as well as Rice Sides packages with the noodle or rice and flavor packets inside, poking a hole in the package with a hole punch, placing 10 of the pouches in a food storage bucket, adding a couple oxygen absorbers, then sealing it up, stating it will last 5 years. I’ve also seen folk’s putting the Pasta Sides pouches, poking a hole in the pouch, then putting the pouches in mylar, sealing the with oxygen absorbers. Those rice and pasta side sell for about $1 ea. I want to know if this is a methid that would work and really last 5 years? Or, do you have a better way of doing it? My concern is that putting the actual puechased pouch from the store in mylar or just in a food grade bucket, the pouch itself may containmate the contents. I’d like to know your thoughts on this method that a lot of people are doing now before I waste money in doing it myself.

  9. 9


    Heya, thanks for the question; sorry for the ultra slow reply, catching up on months of comments…yes, I’m a terrible blogger!! Most of those pouches are dried pretty thoroughly; they are probably good for double their shelf life. If I had to guess, they’d probably last 5 years without doing too much too them! I don’t like the first method of putting the pouches into a bucket and using absorbers, as buckets aren’t airtight and so there is no low-oxy environment there. The 2nd method would work and at least double the shelf life; 5 years isn’t far fetched. As you alluded to, I much prefer taking food out of its original container and putting it directly into Mylar to avoid the potential for bacterial growth.

    For me, there are probably a lot better foods to store than pasta sides, for two reasons. First, they are pretty bulky for the calories you are getting. Second, you have to add water. In a disaster situation, that water might be better used for something else. I’d much rather store canned soup even though its a little bulkier, because it contains its own water and has an essentially infinite shelf life!

    Thank you!

  10. 10


    Yes, absolutely!

    Thank you!

  11. 11


    Foodsavers will seal Mylar bags, however because they don’t have channels, the vacuum function won’t work. One note, because Foodsaver seals also tend to be a little thin, I always recommend doubling up on the seal if using one!

    Thank you!

  12. 12


    I always recommend removing food from the original container to prevent the opportunity for bacterial growth on the packaging.

    Thank you!

  13. Ramona #

    I have just found this wonderful world of Mylar bags and oxygen absorbers, I thought that I did enough research to begin storing my food. I’m having problems with air in about half of my bags, I repackaged the problem bags and increased the absorbers and still about half didn’t set up. I only gave them two days to do their thing should I give it more time?
    Thank you for your time, Ramona from Alaska

  14. 14


    Thanks for the note and questions! Many folks expect all their bags to ‘contract’ like a vacuum seal bag, however that will only happen with some types of foods. As you said you had the same food and tried to seal it twice, I am guessing that you are storing a type of food that does not contract much. For example, oats, flour, and other very dense or very fluffy foods will rarely contract. Also, the amount of headspace in a bag (The total amount of air in a bag after sealing) helps determine if a bag contracts or not. In those cases, all of the oxygen is still removed, but the bag might only contract slightly or unnoticeably. I would also check the seals on your bag; they should be between 1″-2″ thick, and you should be able to squeeze the bag lightly without any air coming out. If you had 10 bags that did contract, and 10 that did not, for example, I think you probably did everything correctly and just got some different results based on your food type and headspace gas.

    Thank you!

  15. Rozz #

    What are the recommendations on using pre-used buckets for long time storage? I have frosting buckets with gaskets given to me by local bakeries. Trying to keep cost down due to a limited budget.
    If you have already posted please direct me, as I am new to your site.
    Thank you for the time it takes you to blog back. Your site is quite informative and easy to use. Thank you.

  16. 16

    Heya, thanks for the note! Feel free to use any bucket that once had food in it from a bakery or restaurant. Just wash it out well with a light bleach rinse. The buckets are more to protect the Mylar bag, so almost any type of bucket will work.


  17. tom #

    When I seal my mylar bags I use a iron.After I make a 2in seal on the bag I use the edge of the iron and go across the place where I sealed the bag.I think this gives a extra thin line of protection.It can’t hurt and it might help to seal the bag.Just a theory of mine.

  18. Pat #

    I was wondering if I need to put desiccants in my mylar bags when storing sugar?

  19. Lin #

    Can I store Bean, rice, etc in fruit jars using oxygen absorbers? If so what
    size? I am new to this and any advice is helpful.

  20. 20

    Sure, you can use canning jars; you want the kind with the ring and seal. Use a 100cc absorber for a 1 quart jar. Try to keep them out of the light if possible, as that can damage the nutrients in the foods you are storing.


  21. 21

    Heya, thanks for the question. If you live in a humid environment, it can be a good idea to reduce the ambient moisture in the bag when first storing.


  22. Linda #

    Maybe I haven’t looked far enough yet but my question is: When using the canning jars to store, how many & what size of oxygen absorbers should I use?
    So far I plan to store rice, oatmeal, cereal macaroni & pancake mix. I have purchased the wide-mouth jars quart size jars. I am a newbie to doing this & I am quite excited about getting started. Thanking you in advance. Linda

  23. Charles R. Gant #

    Just today a friend and I put up for long term storage a variety of dried beans and golden parboiled rice using mylar bags and oxygen absorbers that came in a kit.
    I had wanted to use nitrogen gas that would flush the oxygen out of the mylar bags I used in conjunction with food grade five gallon buckets.
    While getting my needed buckets, mylar bags and the O2 absorbers, I discovered that trying to obtain the nitrogen, regulator and tubing was either expensive or just unavailable for the average consumer like myself.
    So I decided to use dry ice for flushing out most of the O2 out of each mylar lined bucket. I read that using about a 1/4 pound chunk of dry ice in each of the buckets would help to remove the O2. Per directions, I poured a few inches of rice or dried beans into the mylar bag and then pour the remainder of whatever I was preparing for long term storage. I waited for a minimum of an hour for each of my ten buckets. Then with the help of a friend, we manually removed as much air (CO2) as possible, then sealed each mylar bag with a hot iron, leaving only enough space to insert a oxygen absorber into each bag and then a vacuum hose with a small adapter into the small opening we left for that purpose. We removed as much air as we possibly could then carefully finished sealing each mylar bag. We waited long enough to make sure that each mylar bag was sealed properly. Then placed the top on each bucket making sure I had a good seal.
    Within ten or fifteen minutes we noticed that each lid had started bulging outward. So we used the lid opener to release the pressure build up, then made sure each bucket had resealed properly.
    I thought that taking that extra step in the process took care of the problem with the pressure buildup.
    Well, about thirty or forty minutes later and much to my surprise, one of the lids blew off of one of the buckets and the sealed mylar bag was bulging out of that bucket, obviously full of CO2 gas. All I could do was punch a tiny hole in the mylar bag and slowly force whatever gas I could out of the bag, seal the tiny hole and fold the bag back into the bucket and placed the lid back onto the bucket making sure I had a good seal.
    WHAT did I do wrong in what I thought was a carefully done process? Should I have waited another hour or two for the dry ice to finish it’s process or did I do something else wrong?
    I will be storing more “dry goods” in the near future, but not until I find out what I did wrong. Please advise.

  24. 24


    Heya, thanks for the very detailed comment; my very first attempts to store food were with dry ice and CO2 flushing, and I had about the same results! In general, oxygen absorbers are used as a replacement for nitrogen/CO2 flushing. Gas flushing, as you have found out, is a little hit or miss. Plus, flushing removes down to about 5% oxygen (in general) due to its difficulty to regulate and seal without residual air returning. Oxygen absorbers remove down to about .1% oxygen, or about 50 times better. Vacuum sealing alone gets to about 2%, or also quite a bit better than flushing, though still 20 times less effective than O2 absorbers; I would suggest just vacuuming and using absorbers and skip the CO2 flush.

    Good luck!

    Thank you!

  25. Debbie #

    When I repackage dry goods by emptying contents from original packaging to the mylar bags, do I just drop the oxygen absorbers into the mylar bag onto my dry goods. The chemical reaction will not hurt the foods? Do you have a chart showing the approximate length of time foods can be stored without going bad. For example oats, flour, sugar, rice, beans, etc.

  26. 26


  27. Lena #

    If you place a case of canned goods in a vacuum bag and sealed it, would this keep it from rusting? Would place in black bag and store in cool dry and dark place, how long would this increase shelf life?

  28. 28


    Vacuum sealing a bag with cans in it may prevent oxidation (aluminum cans don’t rust per se), however as that is an exterior process, it won’t generally harm your food. Storing in a cool place is the biggest thing you can do to increase the shelf life of canned goods, as the food is already protected from oxygen, light and moisture. There are many products like canned veggies and fruits that can store essentially indefinitely. As time goes on, their taste may change, but there have been cans (and canning jars) opened up from the 50’s where the food still retains a decent percentage (50%+) of its nutritional value, although taste can suffer greatly.

    I hope that helps!

  29. Carmen #

    How should I pack many half gallon bags (already prepared and sealed in individual Mylar Bags) inside a 5 gal. Bucket? Just place all the packets inside the bucket or do I put all the Mylar Packets inside another big Mylar bag inside the bucket?

  30. Jeannine Muto #

    I have a 5lb. pound bucket with a no. 2 in a triangle and, a HDPE on bottom, it’s orange (Home Depot). Is it a safe bucket to store in, I have only seen white storage buckets and wondered if the color would leach through? I have 25 yr. food and though that it would be ok just to store it in, with no oxygen absorbers. Whats your thought on the bucket? Real new at this!

  31. Kim #

    I was wondering if there is a way to use the mylar bags and not have the food come in direct contact with the bag…could I put beans,rice, etc. in a paper bag and put the oxygen absorber between the two bags. I’m worried about mylar plastic chemicals leaching into the food. Thanks

  32. Jeannine #

    I do realize my bucket does not weigh 5 lbs, but do wonder about orange bucket. thanks

  33. 33

    Heya, thanks for the note, sorry for the very slow reply. I don’t get over here much with the twins and the business! The top and bottom layers of a Mylar bag are inert; ie. they are less likely to react with food than the paper in a paper bag. Plus, paper can hold bacteria, where the PET layers of a Mylar bag won’t. Technically you can keep your food in its original packaging, but I always recommend removing it, as the materials in Mylar bags are as ‘clean’ as they come.

  34. Jason #

    I found “” in my search for a way to vacuum seal mylar bags. While the trick you showed worked initially, about a month after I did my first bag, it lost its seal at the place where the food saver piece was inserted into the mylar bag. Is there another work around that works long term?

  35. 35

    I only wanted to thank you for all the help you give people! I read many of the questions and answers and am amazed how many times there are repeat questions. You are very generous. May God bless you and your family

  36. 36

    Do u have to use oxygen absorbs in vacuum pack jar.??

  37. Beth Easterly #

    Please match the comments to your answers using numbers. I enjoyed reading and learning from both, but I was not sure which question you were answering sometimes. Please do not list this as a comment, as it is more of a suggestion. Thanks!

  38. 38


  39. Christine Tran #

    Hi dear ,
    Question,How much time we have to work on the Disccant Or Oxygen Absorber
    Our Products is instant powder drink ,please be advice .What We need for My product gen between the Disccant and Oxygen Absorber.

    Thank You

    Christine Tran

  40. Richard Hogebaum #

    I just received some of your Mylar Bags. They have a zip lock closure on them. Do I still have to use an iron.
    Next question: During an EMP attack, will these hold up or should the Mylar Bags be additionally put into the Faraday Cage? Please answer or send me an email.

  41. Richard Hogebaum #

    Addtional question. I have a 350W Portable Solar unit in like a small suitcase. Would I need a special Mylar Bag to protect the inverter during an EMP. Additionally should it be in the Faraday Cage.

  42. 42

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  43. 43

    Heya i for the first time here. I found this board and I find It truly useful & it helped me out much. I’m hoping to offer something back and aid others such as you helped me.

  44. Bill #

    I have read that there is nitrogen left in the bags after the oxygen absorber does it’s thing, so does that mean you have to add nitrogen absorbers as well to keep things truly fresh?

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