Some time back, we bought a bunch of rice and pasta at Sam’s Club to package up for long-term storage. We got it all together and packaged it. I then proceeded to lose my pictures!
I finally found them (in, of course, the very last place I looked — sorry, old joke), so here they are to chronicle our first experiences with Mylar foil and oxygen absorbers. Unfortunately, I didn’t take as many pictures as I wish I had.
The primary enemies of food in long-term storage (aside from critters) are oxygen and light. For dry goods, moisture also. Oxygen will cause the oils in food to go rancid, and light just generally causes things to degrade. The presence of oxygen will also allow eggs to hatch that are in grain, as well. A friend of mine just lost a bunch of wheat, because she didn’t know how to prepare it for storage.
It is wise to put grains in deep freeze for a week or so to kill the bug eggs. As far as I know, you cannot get grain that is free of bug eggs. The stuff has been grown outside, after all. All you can do is make sure the eggs don’t hatch. Once you take the bags of grain out of the freezer, you let them come slowly back up to room temperature over the next several days. Then you can package the grain.
In this case, I had white rice and pasta. I’ve only had bugs in rice once, even having stored rice for several years. When we packaged rice and beans in 2-liter bottles, I neither froze it nor used oxygen absorbers. I may regret that someday. I may yet freeze it after we move, just in case. But for this day, I had Mylar foil bags and oxygen absorbers.
You probably know about Mylar balloons. They’re the shiny, silvery foil-like ones that stay full of air or helium for a long time. They work well, and the Mylar involved in those balloons is extremely thin (and you cannot use them for food storage). But they give you a clue to the properties of really good Mylar foil.
The balloons are super-thin, with a positively microscopic layer of foil. The other extreme you find in pouch-packed tuna fish. Those pouches are high-quality, thick Mylar foil.
Mylar itself is essentially polyester sheeting. It is stable, waterproof when sealed properly, and gas-impermeable. It is clear in and of itself, and you see it in some foods that are packed in pouches that are similar to the tuna pouches, except they are clear. It’s the same stuff — except the tuna pouch Mylar has an extra feature: a thin layer of metal that makes the pouch opaque (hence, Mylar foil). This blocks out light, helping prevent degradation of the food inside.
Once it was divided up, we poured a bowl into a Mylar bag, added an oxygen absorber, and then ironed it shut.
Overnight, the oxygen absorbers do their work. They pull the oxygen out of the package, leaving the food packed in nitrogen, which does not react with food. Some of the packages end up looking like bricks of vacuum-packed coffee, so you don’t want to squeeze all the air out of the package before you seal it. …Especially with things with hard points, like pasta. You cannot package spaghetti this way.
About 20% of the air we breathe is oxygen. An oxygen absorber is activated as soon as it hits air. When you seal one into a Mylar bag, its contents begin to react with the oxygen, pulling it out of the environment inside the bag. The process is simply rust. All rust is is the oxygen in the air reacting with iron in pipes, water, cars, etc. This has been put to work for food storage. Fine iron filings, packed in a way in which they can react with the oxygen around them without touching the food, rust and leave the nitrogen behind.
This is why you do not squeeze the air out of the package: the volume of air inside will be reduced by 20%. You need to make sure that as it contracts, the bag does not destroy itself by impaling itself with its contents. Also, if there is not enough air in the bag to move around, it will be difficult for all the oxygen to get to the oxygen absorber.
You buy oxygen absorbers to match the size of the bag you are using, and the type of food you are packaging. Oxygen absorbers for damp foods like jerky will be very slightly different from those for dry foods like rice.
I bought my Mylar bags and oxygen absorbers from Advice & Beans.
There are directions online for making your own oxygen absorbers with coffee filters, steel wool, and salt, or with “hot hands”, those heat packs that they sell for hunters. I’d be cautious about using the “hot hands”, since I don’t know if they contain other ingredients that may not be safe with food.