Powder milk, which contains high content of oil and protein, should be packed in the packages with high barrier property. Aluminum plastic package is one of the main packages used for milk powder, which will be elaborated in this article.

Generally, the above-mentioned aluminum plastic packages come in MAP (Modified Atmosphere Packaging) form, where the nitrogen or carbon dioxide are injected into the package to minimize the oxygen contained inside. That’s why the package should have sufficient gas barrier property to prevent the nitrogen or carbon dioxide inside permeating through the package. This article provides a simplified test method for gas permeability of the aluminum plastic film for your reference.

Only differential pressure method can be used to test the gas permeability of N₂ or CO₂. In the tests, the specimen is mounted in a gas transmission cell so as to form a sealed semi-barrier between two chambers. One chamber contains the test gas at a specific high pressure, receives the permeating gas. The gas transmission rate of the test gas can be calculated according to the pressure change of the lower pressure chamber.

In the tests mentioned in this article, the specimens are aluminum plastic film taken from MAP milk powder package. The testing instrument we used for the tests is VAC-V2 Gas Permeability Tester, manufactured by Labthink Instruments Co., Ltd.

Figure 2. VAC-V2 Gas Permeability Tester

Before the tests, the aluminum plastic package for mill powder to be tested should be conditioned in a desiccant container at 23℃ for 48 hours. Then remove the sample from the desiccant container and cut 6 pieces of specimens whose diameter are 97mm. 3 specimens are needed for gas permeability test of nitrogen and carbon dioxide respectively.

After the specimens are prepared, the tests can be performed according to the following procedures.

1)    Mount the specimen. Apply a thin layer of vacuum grease on the external surface of the test chamber. Place a filter paper on the central area of the test chamber. Then put the specimen on the filter paper. Note: Do not apply vacuum grease on the central area of the test chamber.

2)    Tighten the test cell by locking the clamping mechanism.

3)    Connect the gas supply to the gas inlet port of the instrument. Run the software and set test parameters as required.

4)    Then start the test. The test will be performed automatically.

5)    When the tests are finished, the test results will be displayed in the software automatically.

b. Tighten the test cell

With the test results, the milk powder manufacturers can select the suitable packaging materials for their products and guarantee the quality within shelf life.

For more details about VAC-V2 Gas Permeability Tester, please visit en.labthink.com

About Labthink Instruments Co., Ltd:

Labthink Instruments Co., Ltd is one leading supplier of packaging testing instruments, which is headquartered in Jinan, China and operated in Boston, U.S.A.