Just What IS the Big Deal About Mylar Bags and Oxygen Absorbers Anyway?

Back in “the olden days” (i.e. the 1990’s) when people wanted to have Food Storage the choices were to buy #10 cans of dehydrated or freeze dried foods (pricey), pre-packed 5-6 gallon plastic buckets with grains and beans (still pretty pricey) or they could pack up food themselves. Many people had a combination of food in #10 cans, pre-packed buckets and “do it yourself” dried foods in plastic buckets.

Back in the 1990’s and before, there was no such thing as Mylar bags for the “regular” folks back then – only the military had access to Mylar bags, which were developed for the MREs (Meals Ready to Eat) that the military had made up for their soldiers. So the regular folks who wanted to store food used mainly 5 gallon (some 4 gallon and some 6 gallon, but mainly 5 gallon) plastic buckets to put the food in. And then to keep the bugs away, people would either use bay leaves, or dry ice or they would rent a great big tank of nitrogen and get a hose & wand special made so they could flush the food with nitrogen. And there was also vacuum sealing food.

The problem was that a plastic bucket isn’t a true barrier for oxygen or for moisture. And how cool or how warm the storage area was for those buckets had a lot to do with the shelf life of that food. So after 5 or 10 years, the food might be fine or it might have gotten attacked by moisture, causing mold or mildew. And once there was mold or mildew that bucket of food became hog food (oh dear!).

Oxygen absorbers became available around 1999 and then Mylar bags came into the picture after 2000. And why do we care? Just what IS the big deal about Mylar bags and oxygen absorbers anyway?

Well, to start with, Mylar bags that are thick enough for long term food storage are considered true oxygen and moisture barriers when properly sealed. What?? Yes!! A Mylar bag made for long term food storage is a true oxygen and moisture barrier the way a tin can is or a glass jar is. And the bags (usually silver, gold or green) also keep out light. And they don’t break if dropped like a glass jar will.

What are the 4 things that shorten shelf life of stored food?

1. Moisture (Mylar bags keep the moisture out)
2. Oxygen (Mylar bags keep the oxygen out)
3. Light (ha! Mylar bags keep the light out too!)
4. Heat (Mylar bags don’t come with air conditioners, so protecting your food storage from heat is up to you)

Where do the Oxygen Absorbers come into the picture?

The air we breathe is 21% oxygen and 78% nitrogen (and 1% other gases that we don’t worry about). And easy way to look at it is that AIR is about ¼ oxygen and ¾ nitrogen. For long term food storage, we want to get rid of the oxygen BUT WE WANT TO KEEP THE NITROGEN!

Enter the fabulous little oxygen absorber. If you put some rice into a one gallon size Mylar bag there is really rice AND air in the bag. We want to keep the nitrogen and get rid of the oxygen, so we place the correct size oxygen absorber in the bag with the rice and the air. We seal the bag most of the way across, squish out what air we can without going to any extreme measure, then finish heat sealing the bag (more on heat sealing in a bit).

What is going on in that Mylar bag?

Well the rice just sits back and watches as the oxygen absorber goes to work getting rid of the ¼ oxygen, leaving the ¾ nitrogen. And what do you have once the oxygen absorber gets rid of the oxygen? You now have nitrogen flushed food that is in an oxygen and moisture proof bag. And you didn’t have to rent a tank of nitrogen. You don’t have to put the food in the freezer for a week “to kill the bugs if any”. You don’t have to vacuum seal the Mylar bag. The oxygen absorber got rid of the oxygen leaving only the nitrogen, and no bug, egg, boll weevil or uggledy buggeldy can live in a nitrogen environment for longer than 5 days! Your food is protected!!

What about vacuum sealing? Should you vacuum seal the rice and oxy absorber in that Mylar bag?

NO! No? Why not? Well, remember that we really want that nitrogen to be in the Mylar bag. Vacuum sealing removes all except 1-2% of the AIR. So if there is only 1% of the air still in the bag, and the oxygen absorber takes ¼ out (the oxygen part) and leaves the ¾ nitrogen – what is ¾ of an itty bitty teeny weeny bit of air? Why you don’t have enough nitrogen left in there to much good at all. Don’t make it harder than it needs to be.

How to Properly Use Mylar Bags and Oxygen Absorbers

Let’s say you go to Costco and get a 25 lb bag of rice. And you get some ½ gallon Mylar bags and some oxygen absorbers from Optimum Preparedness. The ½ gallon (i.e. 2 quart) Mylar bags hold 3 lbs of rice (and they have a handy ziplock seal for your convenience after you open the bags up to use the rice. Now oxygen absorbers have to be used within one hour of opening the package they come in because they start chomping down the oxygen as soon as the package is opened. I like to use oxygen absorbers that come in 10-packs rather than 50 packs because it is less stressful.

I fill 8 of the ½ gallon Mylar bags with rice (that uses 24 lbs of rice) and then I’ll put some lentils or beans in the other 2 Mylar bags. And I was smart enough to label the Mylar bags before filling them. Once everything is ready I either will be using my regular clothing iron set to high or I’ll use my Optimum Hot Jaw Heat Sealer(it works great, and sharing the expense with someone else can be helpful).

So I pre-heat the iron or heat sealer (some people have used a flat iron for straightening hair with success). Then I open my 10 pack of oxygen absorbers and drop one into each of my 10 filled Mylar bags (and if they have a ziplock I’ll squish out what air I can and zip them closed). Now I am ready to heat seal the outer ½” or so of the Mylar bag. If you are using the Optimum Heat Sealer with the serrated double heat bars, it only takes clamping about 4 seconds to give a perfect seal. If using a clothing iron, you’ll want to use a piece of board or a cutting board under the Mylar bag so you can press down firmly with your iron.

The Mylar gets hot when being sealed but cools off quickly. How can you tell if you got a good seal? Once the Mylar bag cools off, see if you can open the sealed Mylar bag the way you open a bag of chips. Can you pull the bag open? If the answer is Yes, then you need to reseal it. You should not be able to pull a sealed Mylar bag open, even if you are very strong. What does this mean in the real world? This means you better store a good pair of scissors to get into the Mylar bags of food should you want to eat it. Yes you could use a knife, but it won’t be pretty. Mylar is tough. Store scissors.

Sucked in looking vs Not Sucked in looking

What you will notice the next day is that some of the Mylar bags with food in them look like they were vacuum sealed (even though they weren’t). And then for some mysterious reason, some bags WON’T look sucked in. Did you do something wrong? Is something defective? Do you need to re-do the ones that don’t looked sucked in? Did I miss any questions here?

The thing is that most people have seen food vacuum sealed in a bag before and it always looks sucked in. But how many Mylar bags of food with an oxygen absorber have these same people seen? Probably none. So when they see some Mylar bags sucked in looking and some NOT sucked in looking, the ever helpful brain tells them “sucked in MUST be good since that’s how vacuum sealed looks”. And what is the flip side of that coin? If sucked in = good, then not sucked must equal bad. But it is not true. That reasoning is taking vacuum sealing criteria and applying it to a whole different technology – that of Mylar bags and oxygen absorbers.

So when you see some Mylar bags looking sucked in and some not, and your brain wants to tell you BAD! BAD! You just tell your brain that all is OK and is how it should be – remember, with Mylar bags we want all the nitrogen we can get in with the food.

Coming up next: So how long will this food last in storage?

By Teri Simpson
Optimum Preparedness


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