Yogurt is a food produced by bacterial fermentation of fresh milk. A large amount of protein, fat, vitamin and various beneficial bacteria are contained in the yogurt, which are easy to be digested and absorbed by the human body.

Since the yogurt has a very short shelf life, the packaging material used for the yogurt shall have sufficient barrier property to avoid oxidization of those nutrients. There are various forms of yogurt packages including prepak, tetra pak and plastic cup. The production cost of the tetra pak and plastic cup is relative higher so the most common package used by the manufacturers is prepak. Milky white film and black & white film are the two main materials used for prepak. Both of them are co-extruded films. The black & white film containing high barrier resin material can meet the requirement of 14-21-day storage at low temperature for the yogurt.

Generally, the lower the oxygen permeability of the packaging material is, the longer the shelf life of the yogurt would be. This article provides a simplified test method of the oxygen permeability of yogurt package made of black & white film and milky white film. The tests were performed in an environment where the temperature is 5℃ and the humidity is 0%RH, through which the yogurt manufacturer can determine the oxygen barrier property of the packages at low temperature in order to guarantee the quality of yogurt within the shelf life.

The test specimens are provided by one dairy manufacturer which are made of black & white film and milky white film. The testing instrument used for the tests is Labthink’s VAC-V2 Gas Permeability Tester.

Before tests, the samples shall be conditioned at 5℃ in a dry place for at least 48 hours. Then cut 3 specimens from each kind of samples with sample cutter. The diameter of the specimen shall be 97mm.

Then the tests of both black & white film specimens and milky white films can be performed according to the following procedures.

1)      Apply a thin layer of vacuum grease on the outer surface of the test chamber (do not apply vacuum grease on the center of the test chamber). Set one piece of filter paper on the center of the test chamber. Then clamp the specimens in the test cells respectively. Tighten the test cell.

2)      Adjust the test temperature to 5℃ with temperature controller and maintain the humidity of 0%RH。

3)      Set control parameters and specimen parameters and then start the test.

4)      The system will calculate and display the test results automatically after tests.

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.