Everything You Need to Know About Mylar Bags for Food Storage

What are Mylar bags?  Why are they used in food storage?  Do you need them?

Mylar is the Dupont registered trade name for biaxially-oriented polyethylene terephthalate (BoPET).  Strictly speaking, the BoPET film is sprayed on one side with a thin layer of aluminum foil, which reduces gas and light permeability.  It is laminated on the other side with a thin layer of PET, which improves puncture resistance.[1] Mylar bags cost about the same as the #10 cans they have gradually replaced.  However, in contrast to the #10 cans, these bags can be easily sealed at home without the need for specialized equipment, though dedicated sealers do make the project easier.  Mylar bags can also be sealed with a flat iron for straightening hair or a simple clothes iron.

Mylar bags have been in use now for about 20 years.  And yet, people have been storing food against a time of need for thousands of years.  So do you really need to use Mylar bags with your food?

Mylar has its pros and cons.  It is probably a better choice for people who do not want to think about their food--they just want to store it and forget it.  Mylar provides an added layer of protection over storing food in buckets.  It completely prevents gas, light, and moisture penetration, especially in contrast to freezer bags and vacuum-sealing bags, other common choices for food preservation.

However, such an approach is perhaps not the best choice for true preparedness.  It's critical to learn how to prepare the food you store.

Mylar bags are not a replacement for food-grade storage buckets.  They are an adjunct, because the bags, while strong, can still be damaged.  The Mylar-bagged food needs to be stored in buckets as well to protect it from punctures and tears, especially from rodents.  This is because while the metal in the bag may deter mice and rats a little because they don't like chewing on it, the bags are definitely not impervious to damage.

Mylar bags typically range in thickness from 3.5 mil to 7.5 mil.  Most consider the 4.3 mil thickness to be the minimum for use in food storage, as the 3.5 mil still permits some light to penetrate.  Mylar is critical to preventing light penetration. Light degrades the food and accelerates the loss of vitamins and minerals.  This is especially important when dealing with milk products. 

Mylar bags have a distinct advantage over #10 cans in that they can be easily resealed at home.  They should always be sealed as close to the edge as possible, and carefully cut along this edge with scissors when opening. Mylar bags from commercially packaged goods can also be reused.

Mylar bags can be sealed using a few different methods.

• Dedicated impulse sealer.  It's a little expensive but does the job perfectly.
• Vacuum-sealing strip (like in a FoodSaver).  This sometimes works for smaller bags, but often the strip doesn't generate enough heat to melt the two sides together.
• Flat iron for straightening hair.   
• Clothes iron.  This will also require a 2x4 board wrapped with a towel to function as the ironing board.

There are numerous videos on the web demonstrating how to use each of these options.  

Do not make the mistake of combining Mylar bags with vacuum-sealing and oxygen absorbers.  The first reason not to do this is that it is overkill.  The second, and more important reason, is that with most of the gas removed through vacuum sealing, the oxygen absorber will remove remaining oxygen and the bag will be sucked in so much that any "sharp" foods like rice or pasta may puncture the bag.

Mylar bags are most commonly used with dry, low-fat foods such as:

• Grains
• Beans
• Pasta
• Spices
• Milk 
• Sugar
• Salt
• Dehydrated and freeze-dried and vegetables

The debate rages on regarding the best size of Mylar bags to use.  Some people advise against the five-gallon bags, saying they won't eat that much of one kind of food quickly enough.  That's probably true for freeze-dried cheese or powdered milk.  But it's definitely not the case with rice and wheat.  If you are basing your food storage program on lots of grains and beans, you're working through about 30 pounds of grains per month per person.  A family of four could easily go through a bucket a week.  There's really no need to worry about grains going bad in such a short period of time.

Families that rotate through their long-term stores of grains and beans can make do very well without Mylar bags.  As long as these foods are stored in food-grade buckets with good seals, and protected from light, heat, moisture, and odors, they should be good and fully nutritious for at least five years.  Save the Mylar bags for freeze-dried and dehydrated foods that are used less frequently.

Links to related posts:
Oxygen Absorbers

[1] https://en.wikipedia.org/wiki/BoPET

 08.07.20