Many packaged edible products require protection from the gain or loss of moisture. Isolation from oxygen which causes spoilage from bacterial action and oxidation. Food products also need protection from other human made gases such as hydrocarbons.
Plastics most often provide adequate protection against moisture, oxygen and other gases whilst also providing the feature of flexibility. For many years, glass and metals dominated packaging edible products. However, plastic films provide the unique charateristics of flexibility, weight and space saving than the rigidity of glass and metals and so enables the packaging of delicate food products some of which might not otherwise get packaged at all.
Plasatic films also allow the introduction of inert gases such as Nitrogen or Carbon Dioxide into the package to remove the air from the wrapped headspace to increase the shelf-life of food products.. This preservation technique and method is termed Modified Atmosphere Packaging (MAP) and the material used in packaging should contain a low porousness to oxygen to avoid contamination.
Controlled Atmospheric Packaging (CAP) is an another advanced preservation method. The approach is applicable to fresh, unpackaged produce. In this case, containers selectively penetrable to oxygen, ethylene, and CO2 surround the perishable foods. Moreover, if the container’s permeability to the three gases occurs within a specific range, preservation occurs as a result of the slow variation in atmosphere within the package which is ideal for conservation. Perforating the film is a crude method to provide permeability/portability which sacrifices the gas barrier and the controlled atmosphere .