Packing Functions and Relevant Test of Nitrogen Gas

As the theoretical research on package is developing, people  have discovered that the contents of nitrogen gas, carbon dioxide and other gases in inner package could also impose influences on the content, with food and medicine being the most sensitive.
1.Packing Functions of Nitrogen Gas and Modified Gas Package
For the reason that gas density of oxygen, carbon dioxide and so on can cause quality deterioration of food and medicine, vacuum packing (i.e. to extract inner gases with vacuum equipment after the plastic film package of products is finished) was originally adopted to reduce such effect. Vacuum package got a widely applications in the packing of prepared food, salt sacrificial product, and bean product. However, there are still some problems appearing during actual application:
1. Since there is almost no gas existing in inner environment, packing materials will adhere to the content surface. If the product is angular or fragile, package breakage or damage of inner content becomes very possible in courses of transportation and storage.
2. Pressure difference on two sides of the package material is rather big, which facilitates the transmitting of external gases into inner package. Generally, oxygen and carbon dioxide that can influence the quality of inner content has higher demand for permeability than inactive gases such as nitrogen that exerts no influence to the content. Materials with better barrier property should be employed to reduce oxygen permeance. However, packing costs will correspondingly increase.
3. Vacuum package is not suitable for some food. For example, plucked fresh fruits and vegetables still have expiration, and the vacuum package of them will result in the reproduction of anaerobic bacteria.
Improving on the basis of vacuum package, modified air package (MAP), also called air replacing package and gas filling package, adopts inactive gases such as nitrogen to replace the gas within package. According to the aerobic metabolism characteristics of aerobic microbe, this method realized the purpose of mildew proof and prevention of corrosion and preservation by reducing oxygen density through changing gas ingredients of package, during which physiologic activity, mildew activity and rate of respiration are inhibited. In this process, inactive gas nitrogen is the filling gas and plays the role of maintaining positive pressure of inner package. In addition to protecting inner product through preventing extern gases from transmitting in, nitrogen gas can efficiently prevent content transformation and content breaking under pressure without influencing package appearance and printing effect.
2.Important Test Items of Modified Air Package