All types of plastics are not gas-proof. Therefore oxygen will diffuse into plastic packages. As result the packaged goods can loose their properties. Food will for example change its taste and/or its color. The result is a short shelf life. For a long shelf life and a good quality of packages goods, it is important that packages have a good oxygen diffusion barrier. This can be achieved with plasma coating.
The amount of diffusing in oxygen can be expressed by the oxygen transmission rate (OTR). The OTR describes what oxygen volume diffuses thorough a defined area during a defined time. The OTR is therefore an important benchmark for many packaging applications
To answer this one must know more about the packaged good. There are 2 different ways of calculating the necessary OTR:
For the first way see the next section about the oxygen level calculation. The second way can be used if one doesn’t know much about the oxygen limits of the particular product, because one could look in literature for limits. Tab. 1 lists some limits for different classes of food.
Tab. 1: Oxygen ingress limits for different types of food with values from R. B. Armstrong, “Effects of polymer structure on gas barrier of ethylene vinyl alcohol (EVOH) and considerations for package development,” in Tappi Place Conference 2002.
Canned milk, meats, fish and poultry
1 - 5
Beer, ale, wine
Canned vegetables, soups, spaghetti, catsup, sauces
1 – 5
5 – 15
Carbonated soft drinks
10 – 40
Fruit juices, drinks
50 – 200
Jams, jellies, syrups, pickles, olives vinegar