With the rising environmental problems caused by “white pollution”, the public has been aware of the significance of the environmental protection. Under such circumstances, environment-friendly packaging materials are introduced to replace the common plastic packaging materials. Biodegradable material is one kind of such materials, which has been widely used in the packaging industry.

Modified starch, also called starch derivatives, are prepared by physically, enzymatically, or chemically treating native starch to change its properties so that it can be used in many applications. Modified starch is one main material that is used to manufacture biodegradable film, which is usually used in package for cakes, frozen food, sweets, cooked food, fresh fruits and vegetables, etc. The oxygen barrier property of the modified starch film may directly influence the quality of the contents inside the package in storage, which shall be tested before use.

This article provides a simplified test method of oxygen permeability of the modified starch film. The test specimen used for the tests are supplied by one scientific research institute. The testing instrument used for the tests is Labthink’s VAC-V2 Gas Permeability Tester, which adopts differential pressure method where the pre-conditioned specimen is mounted in the gas diffusion cell as to form a sealed barrier between two chambers. The lower-pressure chamber is firstly evacuated, followed by the evacuation of the entire cell. A flow of gas is thereafter introduced into the evacuated higher-pressure chamber and a constant pressure difference is generated between two chambers. The gas permeates through the specimen from the higher pressure side into the lower side. The gas permeability and other barrier properties of the specimen can be obtained by monitoring the pressure changes in the lower chamber.

The tests shall be performed according to the following test procedures.

Figure 1. VAC-V2 Gas Permeability Tester

(1)    Cut 3 pieces of specimens from the provided sample of modified starch film. The diameter of the specimen should be 97mm.

(2)    Apply a thin layer of vacuum grease around the 3 test chambers respectively and since the modified starch film is fragile, a filter paper shall be placed under the specimen as a support to prevent any fragment entering the internal part of the instrument. The diameter of the filter paper should be 65mm. Then tighten the test cell.

(3)    Set specimen name, test temperature, test humidity and other parameters.

(4)    Click Test to start test. Turn on the vacuum pump and the system will be evacuated automatically.

(5)    The test results of the 3 specimens will be automatically displayed after tests.

Figure 2. Mount the Specimen

For more details about VAC-V2 Gas Permeability Tester, please visit www.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.