Want to learn about why Slow-Acting Oxygen Absorbers for Freeze Dried Foods are better? Check out our video here.
What are oxygen absorbers and how do they work?
Oxygen absorbers employ a foundational metal (iron) and a simple chemical reaction (oxidation) to effectively eliminate and trap oxygen within their enclosed packets. Upon opening a packet, you'll notice a dark gray or black substance, which consists of powdered iron. As the absorber is utilized, the material inside gradually becomes slightly rigid and crunchy, eventually taking on a reddish-brown hue.
How do I use oxygen absorbers with Mylar bags?
Each oxygen absorber is designated with a rating indicating the volume of oxygen it can absorb, typically measured in cubic centimeters (CC). For instance, a 300cc oxygen absorber has the capacity to remove 300cc (0.3 liters) of oxygen from a sealed environment such as a Mylar bag. However, considering that approximately 80% of air consists of nitrogen, the absorber only needs to eliminate the remaining 20% composed of oxygen. Following the 4:1 or 80:20 ratio, an oxygen absorber can effectively clear an airspace approximately five times its designated rating. Thus, for example, a 300cc oxygen absorber can clear the air from an empty bag or container with a volume of up to 1.5 liters (300cc x 5).
However, in practical use, since our bags are predominantly filled with food rather than air, we can employ a higher ratio of oxygen absorber to bag size. This explains why, for instance, we approximate that a 300cc oxygen absorber can adequately clear the oxygen from a one-gallon Mylar bag.
How many oxygen absorbers should I use?
A commonly recommended guideline is to utilize 300-500cc of oxygen absorber per gallon of stored food. Here's a simplified chart illustrating this principle:
1 Quart Bag: 100cc oxygen absorber
1 Gallon Bag: 1-2 300cc oxygen absorbers
2 Gallon Bag: 2-500cc oxygen absorbers or 1-1000cc oxygen absorber
My bag didn't shrink/contract, are my absorbers bad?
In nearly all instances (99%), this is certainly not the case! Our oxygen absorbers are trusted by food processing companies globally, and they wouldn't endorse a product that only functions intermittently. There are several factors that might prevent your bags from contracting.
The first and most prevalent reason is the seal of your Mylar bag was not complete, either due to under or over-heating. I recommend double sealing when using an impulse sealer, and making sure all the material above the tear notch is sealed.
Second, powders such as flour or freeze dried eggs won't show contraction. However, you will be able to tell your oxygen absorbers worked by checking the 'bubble' at the top of the bag near the seal. Both sides of the bag will be pulled together if your food is sealed properly.
Third, depending on the amount of headspace you have, you may not have used sufficient oxygen absorbers for the size of the bag. Also, too much headspace (air in the bag) may cause the bag to contract around the empty space and be less noticeable. I always recommend squeezing out as much as air as possible from a bag before sealing to require less of the oxygen absorbers capacity to clear the bag.
Furthermore, when using oxygen absorbers with foods possessing very low moisture content, they may take longer to activate, which is perfectly normal. While oxygen absorbers can sometimes work within hours, in extremely dry conditions, it may take up to a week or more to completely remove oxygen from a container.
Lastly, make sure you are using a sufficient quantity of oxygen absorbers for their storage needs. It's important to remember that if you're using 5-gallon bags but purchasing 100cc oxygen absorbers, you'll need to use 20 or more absorbers per bag!
Should Mylar Bags Contract?
The short answer is that almost all bags will contract with the exceptions of powders or bags that have a significant amount of air left in them when sealing. The longer answer with an experiment we did is here. Some food storage companies may tell you your bags not contracting is normal; however with the exception of powders we have seen contraction with almost all types of food. If you are unsure whether your bags should contract, let us know what type of food you're storing and we'll test it ourselves and send you the results.
