Glass with a rubber seal is right for a year of eating. Mylar with an oxygen absorber is right for a decade of storage. They are not interchangeable.
Pick by how long you need it
For food you will eat within a year, a glass jar with a rubber gasket in a dark cupboard is enough, and it lets you see what is inside. For food you are putting away for years, mylar with an oxygen absorber is the only one of the two that removes the oxygen driving the slow decline in colour and flavour.
Vacuum sealing sits in between. It removes most of the air but the bags let a little oxygen through over time, and they puncture.
What an oxygen absorber actually does
It is a sachet of iron powder that rusts, pulling oxygen out of the sealed space and leaving mostly nitrogen behind. That stops oxidation, which is what turns dried apple slices brown and makes stored fats taste stale.
It does not remove moisture. If a batch was not dry enough going in, an absorber will not save it. A desiccant does the opposite job and should not be used with dried food you plan to eat, because it will pull moisture from the food into itself.
Sizing absorbers
Match the absorber to the empty air space, not the food weight. A rough working rule is 100 cc for a one litre jar, 300 cc for a gallon sized mylar bag and 500 cc or more for a five gallon bucket liner.
Oversizing is harmless. Undersizing leaves oxygen behind, which is the failure most people do not notice until years later.
How to tell a seal has failed
In mylar, a good seal goes slightly hard and the bag pulls tight against the contents within a day. A bag that stays soft and loose either has a weak seal or a spent absorber.
In glass, look for condensation, a lid that no longer holds any resistance when you open it, or fruit that has gone from leathery to sticky.
| Method | Realistic shelf life | Best for | Drawback |
|---|---|---|---|
| Glass jar with gasket | 6 to 12 months | Everyday fruit, vegetables, herbs | Light and oxygen still reach the food |
| Vacuum sealed bag | 1 to 2 years | Portions, jerky in the freezer | Punctures, slow oxygen ingress |
| Mylar plus oxygen absorber | 5 to 25 years | Long term stores, freeze dried meals | You cannot see inside, single use |
| Freezer, sealed | 1 to 2 years for jerky | Anything with fat in it | Uses freezer space, needs power |
Safety note. Shelf life figures are quality estimates from published guidance, not safety guarantees. Dried food that shows mould, off smells or stickiness should be thrown out, whatever the date on the jar.
What this is based on
- USDA guidance on storing dried foods
- National Center for Home Food Preservation, packaging and storing dried foods
- Oxygen absorber and mylar manufacturer documentation