Research On A Continuous Technology Of Modified Atmosphere Packaging And The Gas Exchange Device

Modified atmosphere packaging (MAP) is a new fresh keeping package which is developed from the vacuum packing and filling in nitrogen package. The environment in the trays or bags is changed to slow down metabolism and extend the shelf life of products. It is most important for the fruit modified atmosphere package to ensure that the gas component in the original package is high accuracy.Currently, the existing basic packaging method of MAP is bag or tray. The mainly gas replacement types contain gas flushing and vacuum filling replacement. The gas replacement device is the key parts of the modified atmosphere packaging machine. Its property directly affects on the quality of gas displacement, gas replacement rate and the consumption of the displacement gas. Also, it directly determines the quality of the product package. Up to now, it has been manufactured many kinds of gas replacement structures at home and abroad. But it is short of theoretical analysis and technique in the optimization design of the gas replacement device to improve the properties of the machine. The gas replacement rate is the key indicators to evaluate the quality in the package container during the MAP process. It is an effectively mode to optimize the gas replacement structure by using the numerical simulation. This paper makes use of computation fluid mechanics. Gas replacement device is one of the key technology devices in MAP machine. A physical model is established in order to analyze gas flushing and vacuum filling replacement process depending on the gas replacement mechanism.The gas flushing replacement is commonly used in the type of trays gas replacement. According to the existing pore structure in MAP machine, the numerical simulation is used to analysis the gas flow field, at the different jet injection angles. Effect of the jet injection angles and filling pressure on the gas replacement rate was analyzed.The vacuum filling gas replacement can reach the high accuracy gas replacement rate, but the cycle of package is relatively long. The continuous MAP machine which is designed by us is the physical model to establish the three-dimensional gas flow field. The models compare the effect of gas replacement properties for the factor of three different pumping structures, the range of pressure and fruits. Especially the change of gas component process is emphasized to analysis.According to the result of numerical simulation, the jet injection angles are optimized for the existing gas flushing device to improve the accuracy of gas replacement. The optimal parameter can be acquired for the vacuum filling device designed by us. It can supply a theoretical direction for the continuous, precision and quick package technology. A design proposal is predestined for it to ensure accuracy of gas replacement and productivity effect of package.