In the 1950’s, a company called DuPoint developed a polyester film for NASA called BoPet. BoPet film is more commonly known as Mylar and NASA first used it to insulate and protect its space crafts from the heat of the sun. Today Mylar is used for a variety of things, including food storage bags, and that is because Mylar food storage bags do a great job of blocking oxygen, moisture, and light from getting in the bags and ruining the food inside.
Other kinds of bags are less effective for storing food long term because oxygen can seep through them slowly over time and they don’t protect the food from light. So when it comes to long term food storage bags, Mylar bags are the best choice.
Of course in addition to the Mylar bags you will also need oxygen absorbers for food storage and food storage buckets which we talk more about in separate articles. Oxygen absorbers to put in the bag to absorb any remaining oxygen that got in the bag before it was sealed, and buckets to put the bags in for extra protection from things like rodents which can eat through the bag. .
In this article we’re going to talk more about Mylar bags for food storage so that you’ll know exactly what kind of bags to get and how to use them.
What kind of Mylar food storage bags do you need?
First of all, you need to be aware that some companies don’t call their bags “Mylar bags” even though they are. They may have another name like “moisture barrier bags” or “metalized storage bags”. Either way, they should be alright as long as they’re made for food (food grade).
4.5 mil is a good thickness for a Mylar bag. Some are even thicker than that. 3.5 mil is also popular, but I wouldn’t recommend them because if you hold them up to the light, they say the light can shine through them.
If you’re using 5 gallon buckets, than 5 gallon size Mylar bags are the largest size you’ll need. If your storing only one food in a 5 gallon bucket than that will work just fine. If you’re storing more than one food in the same bucket than you can use smaller size bags like 1 gallon bags or quart size bags and have separate bags for each food.
You can also purchase zip lock Mylar bags. But, for long term food storage, they still need to be sealed above the zip lock. Some of them are already heat sealed on the zip-locked side. You just fill them and seal them from the bottom. And you have to tear the sealed top off when you’re ready to use them. That will give you access to the zip lock so you can store them a bit longer.
Other zip lock Mylar bags have to be filled from the zip lock side and are already sealed on the bottom. If you get those kind, just make sure you heat seal the top shut above the zip lock if you plan to use them for to store food long term.
How to store food in Mylar bags
If you’re filling a 5 gallon bag with food, you’ll want to line it inside the bucket first with the top open. That way the bucket will hold the bag while you pour the dry food inside. If you’re using smaller bags, you might need to be more careful when pouring the food in. Always leave enough room at the top of the bags so you can seal them shut.
Storing more than one food in the same bucket has its advantages. That way you don’t have to open a whole 5 gallons worth of beans or rice at a time for example. And you can combine different foods in the same bucket that together will make up a meal. Just keep each food in a separate bag and give each its own oxygen absorber.
Oxygen absorbers are measured in cubic centimeters or cc’s. A 2,000cc oxygen absorber is usually recommended for a 5 gallon bag, and for a 1 gallon bag you can use a 300cc oxygen absorber.
Desiccant aren’t usually needed in the smaller bags, but you might need them in a 5 gallon bag if you’re storing something like sugar or salt in them that can get rock hard from moisture. A desiccant will absorber the moisture and keep the food from sticking together.
For most of the dry foods commonly stored with this method you probably won’t need a desiccant at all. But, if you do use one, make sure to put it in first below the food and put the oxygen absorber in last on top of the food. Don’t put the desiccant near the oxygen absorber or it can effect it.
How to seal mylar food storage bags
As soon as you get your oxygen absorber into the bag with the food, you want to seal the Mylar bag right away. Oxygen Absorbers work quickly once exposed to oxygen so you need to work fast so they don’t get used up by the oxygen in the room.
To seal the Mylar bags, you can either use a heat sealer designed for this purpose, or a clothes iron or hair straightener. If you use a clothes iron, you need a flat surface to work on. A lot of people just put a board or level across the top of their bucket and heat seal the top of the bag on that.
If you have a bag with something really fine like flour in it, make sure to whip the inner lip of the bag off first before sealing.
Always check your oxygen absorbers before using them to make sure they’re still good. Squeeze them between your fingers, if they feel soft they’re still good. If they feel like they’re getting hard, don’t use them – they’re no good.
It’s also a good idea to come back and check your sealed bags a few days after you’ve sealed them. If the oxygen absorbers are doing their job, the bags should have compressed a little.