Not all Bags are Created Equal (Quick Lesson on OTR)
Vacuum packaging is a method of packaging that removes air from the package prior to sealing the package. Many food industries (meat, cheese, seafood) use vacuum packaging in order to extend the shelf life of these products. Once air has been eliminated from the package, there must be an adequate oxygen barrier and seal integrity to keep a low oxygen concentration inside the bag. Otherwise, the driving force created by the oxygen partial pressure differences (21% outside the bag and 0-2% inside the bag) will cause oxygen to re-enter the bag.
OTR (Oxygen Transfer Rates) is the amount of oxygen that passes through a defined area of film over 24 hours. This is where the importance of your bag comes in. See our chart below of various OTR rates for films. The lower the OTR, the better the barrier.
If you are vacuum sealing a bag with a high OTR, this defeats the purpose of vacuum sealing since the bag will easily allow oxygen right back in the bag. In order to properly vacuum seal your bag, you must choose a bag with a low OTR.