Food Storage FAQ
Comprehensive Food Storage FAQ v. 0.1.5
What is an Oxygen Absorber?
An oxygen absorber is a small packet of material used to prolong the shelf life of food. They are used in food packaging to prevent food colour change, to stop oils in foods from becoming rancid, and also retard the growth of oxygen-using aerobic microorganisms such as fungi.
The active ingredient is an iron oxide powder, which when it chemically reacts (ie. rusts) removes oxygen from the atmosphere.
How do I know when an oxygen absorber is working?
The most obvious sign an oxygen absorber is working is that it gets warm. When continuosly exposed to oxygen, some can get so hot as to be uncomfortable to touch, and will often form condensation on the inside of the outer package.
How do I know when an oxygen absorber is used up or no good?
This is one of the most frequently asked questions we get. The easiest way to tell if an oxygen absorber is good is to pinch the packet. If it feels ‘soft’ or powdery, the iron oxide powder is still in its original state and it is good. If it feels ‘hard’ or like a solid wafer in the packet, it is completely spent and should be replaced.
How long should it take for my absorber to remove all the air from my bag?
Some conditions are better than others for the speed at which an oxygen absorber works. For example, in a very dry climate, it might take up to a week for an absorber to fully activate. In a warm, humid climate it might take only 48 hours.
Why don’t some of your absorbers have the little pink pill in the pack?
This is another very common question. There are two main reasons. The first is it adds to the cost of the product. The second is that the pill doesn’t really tell you what you think it does. The pill (it’s official name is an Oxygen Indicator Tablet) only tells you that there is one good oxygen absorber in the pack, not that the entire pack is good. For example, if only 1 oxygen absorber in a pack is good and 49 are bad, the pill will still show pink. If the packets have been exposed to oxygen and 90% of their absorbing capacity is used up and only 10% remains, the pill will still show pink.
It is inifitely preferable that you use the ‘pinch method’ above to determine whether your absorbers are good, not an indicator tablet.
So what’s the history behind the pink pill?
The original seller of oxygen absorbers in the US for long-term food storage included these in the packaging. Interestingly, for them to get the pill into the packaging requires opening vacuum-sealed master bags, dropping in a pill, and resealing the pack. Thus, the factory-sealed packs we sell have been exposed to less air than the packs that have pills in them, making them more likely to be usable, not less.
How many oxygen absorbers should I use?
For 1-gallon bags, you should use 1-2 300cc oxygen absorbers. For 5-gallon bags you should use 5-7 300cc oxygen absorbers or 1 2000cc oxygen absorber. You should adjust this number up a little bit if you are storing less dense foods, such as pasta or some lentils, because the bags will contain more air even when full in comparison to very dense foods such as rice or wheat.
Do I need to use oxygen absorbers with everything I store?
Most foods will benefit in longevity when using oxygen absorbers. However, they are unnecessary when storing sugar or salt. In some cases, using an absorber with these foods will cause signficant clumping, although it won’t harm them otherwise. Also note that some foods may not store well for long periods of time no matter the method used (for example flour, yeast and some spices).
I ordered 20/50/100 Oxygen Absorbers, I’m definitely not going to use that many…what should I do with the rest?
The easiest way I’ve found to store oxygen absorbers is to use a small mason jar with a gasketed lid. You’ll know you have a good seal because the absorbers will pull the pop-top down. Try to use the smallest jar possible to minimize the work the absorbers you are storing need to do to clear the jar. You can also re-vacuum seal the absorbers in their orginal or another oxygen barrier bag.
What is Mylar?
BoPET (Biaxially-oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical and dimensional stability, transparency, reflectivity, gas and aroma barrier properties and electrical insulation.
A variety of companies manufacture boPET and other polyester films under different brand names. In the US and Britain, the most well-known trade names are Mylar, Melinex and Hostaphan.
Wait, your Mylar bags aren’t clear; what’s up?
The polyester film is combined with a foil layer and in some cases another sealent layer of LLDPE (Linear Low-Density Polyethylene); this allows for good heat-sealing, UV protection, low odor transmission, and high puncture resistance.
How do I seal Mylar bags?
Please see this post and video about sealing Mylar bags. Mylar can be sealed with a variety of devices, including a hotjaw sealer, clothes iron, or hair straightener.
OMG, I can see pinholes of light coming through the Mylar bag, why is that?
All foil structure Mylar bags will have small pinholes in the foil layer. There is actually a measurement, ‘Pinholes per meter squared’, that is part of the specification of foil bags. Pinholes affect all foil structures, from a thin 2.5mil bag to the thickest 7-8 mil bags. The other transparent layers of the bag keep the integrity of these bags, and it is only very rarely (less than 1/100th of 1%) an actual ‘pinhole puncture’.
Why don’t my bags get hard when I use an oxygen absorber?
This is our third most common question. While there will be some compression of the Mylar bag after sealing due to the oxygen absorber, an absorber is only removing the 20% of the atmosphere in the bag that is oxygen, leaving the 80% that is nitrogen intact. Also, when sealing bags make sure you remove as much of the ‘headspace’ as you can; this is the area at the top of the bag you seal. Even a little headspace can use up much of the power of the oxygen absorber.
You Folded the Bags, eek! Does folding hurt Mylar Bags?
The short answer is no, folding does not hurt Mylar bags. The longer answer can be found here explaining why.