Mylar is a trade name for a material called BoPet. It is a polyester film first developed in the 1950’s by DuPont and first used by NASA.
Mylar is “Biaxially oriented polyethylene terephthalate” or BoPet, which is a polyester film made from stretched polyethylene terephthalate.
Mylar has a high tinsel strength and its oxygen, moisture, gases, odor and light barrier make it ideal for long-term food storage. Light, certain gases, moisture, and oxygen will reduce the shelf life of non-perishable foods.
Will Mylar Flake Off Into the Food?
Mylar is made using a laminating process and thus there are layers, when making food grade material. Usually Mylar “food storage bags” of quality have an inner layer of aluminum foil. The layers are solid and thus flaking will not occur when used as intended.
Certain manufactures use “metalized polyester”, which is not necessarily Mylar, as it is generally known. It is marketed as a less expensive replacement to aluminum foil, and is very similar in looks and texture to Mylar. Metalized polyester will not have an inner layer but instead will have what is essentially a metalized coating. Often time pre-packaged foods and snacks, such as potato chips come packaged in this material.
Use of the term Mylar is often times used to refer to any polyester film or plastic sheet. Mylar however, is a registered trademark owned by DuPont Tejjin Films and refers to a specific family of plastic sheeting products made from the resin (PET) Polyethylene Terephthalate. The generic name for this material is Polyester Film.
Mylar bags with the inner foil layer can be used to prepare foods using hot water if for example; you want to reconstitute freeze-dried or dehydrated foods.
There are of course materials out there that claim to be Mylar when in fact they are not, so it is incumbent upon you to make sure what you are using is Mylar and that it is rated for food storage.
Mylar bags specifically designed for food storage are FDA approved, they can be heat-sealed using a clothes iron or a vacuum sealer that has a heat strip, or by other methods and may come with a Ziploc mechanism.
The thickness for the bags can range from 3.5mil up to 7.0mil and they come in various sizes. You can purchase Mylar bags, for example, that are used to line five-gallon food grade plastic buckets for added protection. Typically, you would use buckets or other containers along with Mylar bags for rodent and insect protection. Mylar is not puncture resistant so rodents or any animal and certain insects can do damage to the bags.
If using five-gallon bags to line buckets place the bag in the buckle and then fill with your food. Leave several inches at the top and tap the bucket on the floor a few times to make sure the product has settled and has pushed out any oxygen chambers. Pull any slack out of the bag by grabbing the corners and pulling up. Then place your oxygen absorbers inside if using them. Lay a board across the bucket to lay the bag opening on for heat-sealing while still in the bucket.
You can essentially purchase any size Mylar bags you want for packaging snacks, cereals, or entire meals in one bag. Many bags come with a Ziploc mechanism but can still be heat-sealed. The Ziploc technology allows you to get in and out of the bags frequently without ruining the bags. Once done you can refill and Ziploc closed or reuse for something else and heat-seal instead.
When purchasing Mylar bags for storage there are various grades available and for long-term storage, it pays to go with quality. For best results, the bags should state they have an FDA approved sealant layer. This means the bag material is layered for greater protection with a middle aluminum layer.
Food grade aluminized Mylar does meet with all of the FDA’s requirements and it is safe for contact with all food types except alcoholic.
Can You Use a Vacuum Sealer with Mylar Bags?
The short answer is no, because bags designed for vacuum sealers are textured. The texture is needed for the sealer to work properly, whereas Mylar has a smooth very “slick” surface. Certain bags designed for sealers are ribbed or channeled, as well, which is apparently needed for some vacuum sealers to be able to draw the air from the bag.
There are certain vacuum sealers that may work or work more efficiently when it comes to vacuum sealing Mylar bags.
However, some people claim to have been able to place one of the sealer bags inside of a Mylar bag, draw the air out and then seal the both the Mylar bag and the clear plastic bag with the heat strip. Another thing you can try is to seal the Mylar bag and then put it inside of a textured bag and vacuum seal it. You have to decide if all the effort is worth it however. You will have to experiment, but the fact that you can heat seal a Mylar bag is more than adequate for long-term storage.
If you manage to figure out how to vacuum seal your Mylar bags then there really is no point in putting in oxygen absorbers, because the oxygen is removed during the process. You would use the absorbers if simply heat-sealing Mylar, because it would be impossible to remove all of the air. Once the food bag is opened to ensure quality add a fresh oxygen absorber if resealing.
There are videos and instructions on the Internet of people that have had success with using vacuum sealers. Keep in mind the length of time the bag would stay sealed and the number of bags you may damage experimenting. It can get costly and once again, you have to decide if you want to attempt it.
Keep in mind vacuuming sealing may damage some foods and/or make them more susceptible to damage and the sealing can cause damage to the bag as well. Pasta and other products can puncture the bag as the air is drawn out.
What Are Oxygen Absorbers?
As the name implies the little packets draw oxygen away from any material including foods and they are ideal when storing foods long term in Mylar bags. The oxygen absorber packets must be kept sealed, so once you have removed what is needed from the original packaging re-seal it with your vacuum sealer, otherwise their efficiency will be reduced.
There is no true test to determine if an oxygen absorber is still working or not. However, fresh ones usually are soft and feel like they are filled with baby powder or even cornstarch, while those that have been around awhile tend to harden up and the material inside the packet feels coarser.
There are various sized absorbers for various sized storage containers but if you only have the ones that say they can treat a gallon sized container you would simply add five packets for a five-gallon bucket. The packaging will tell you what sized container each oxygen absorber will treat.