Abstract: This article outlines the packaging principle, preservative gas and application of Modified Atmosphere Packaging(MAP). It also presents detailed reasons why gases have different permeability on the same material.

Modified Atmosphere Packaging (MAP) is a kind of preservative packaging developed on the basis of vacuum and nitrogen-filled packaging and it is mainly used for food preservation.

The packaging principle of MAP is to replace gas in packaging with preservative gas (mixture of 2～4 gases according to food property). The external environment of packaging food would be changed, which can restrain growth of bacilli and slow down the metabolic rate and extend the freshness date or shelf life of food. Take fruit and vegetable preservative as an example, fresh fruit and vegetable still respire after pick. They consume oxygen and produce carbon dioxide, which would result in carbon dioxide content increase and oxygen concentration decline in packaging. With high gas permeability film, oxygen could be supplied and carbon dioxide be vented through exchanging packaging gas with atmosphere. When the gas permeability rate equals to respiratory rate of fruit and vegetable, certain gas equilibrium concentration in the package is achieved. Then, fruit and vegetable could maintain weak respiratory rate without progressing anaerobic respiration. Thereby,the maturation of fruit and vegetable is retarded and freshness is preserved. MAP could ensure food texture, nutritional ingredient and freshness date without applying preservative and additive.