What is Mylar and Why is it Best?

Harvest Right mylar bagThe very best way to store freeze-dried food for long term is in Mylar bags, but what is Mylar? Officially called BoPET (biaxially-oriented polyethylene terephthalate) the metallic-looking film is best known by its common trade name of Mylar. Mylar can be used in a number of ways including in balloons, as insulation, in kites, for packaging, or to make blankets for marathon runners. Of course, one of its main uses is in food storage.

What makes Mylar so good for storing food is that it’s extremely light, flexible, tight, and thin. At the same time, Mylar is very strong and durable. The tightness of Mylar is great at isolating stored food from other environmental factors. Tight Mylar bags help control and limit the main factors that can destroy food – oxygen, moisture, and light.  The tensile property of Mylar also helps keep out any unwanted aromas.

When using Mylar bags to store food, it is still advised that you include an oxygen absorber in the bag before sealing. This will help ensure that the freeze-dried food that you are storing is oxygen-free and will keep for a very long time.

Mylar bags can easily be sealed with heat. A bag sealer or even an iron can be used to seal Mylar bags. Be sure to only seal the top inch or so of your bag. Mylar bags can be reused and resealed. If you are careful when opening a bag and end up not using all the freeze-dried food at that time, you will be able to reseal the bag.

Rodents and insects are still able to chew through Mylar, so for long-term storage it is best to store sealed Mylar bags in buckets or plastic bins. It is also recommended to not store freeze-dried food (regardless of packaging) in extreme heat. Food should be stored at below 85 degrees (preferably much lower).

When stored correctly, freeze-dried food sealed in Mylar bags will last up to 25 years.


The numbers on the dial of the sealer correlate with the thickness of the mylar bags. The bags that come with your freeze dryer (and the ones purchased on our site) are 7 mil. So you would set your sealer at 7.

I have had my freeze dryer for about 4 years now. I JUST learned something new. I didn’t know how to set the time on my impulse sealer, I just guessed which time was correct. Thank you for that tidbit of info, very helpful!!

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