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.

Considering the production demand and edible convenience, most of the yogurt products are packed inside cups. Yogurt cups are commonly white plastic cups made of PP, PS and PE. Some others are made of paper plastic composite materials.

In order to prevent the yogurt from oxidization or deterioration, the yogurt cup must have sufficient oxygen barrier property. Generally, the thickness of the cup wall and the density of the material are proportional to the oxygen barrier property of the yogurt cup. However, the oxygen transmission rate should be tested to evaluate whether the yogurt cup can meet the requirements for oxygen barrier property so that the yogurt can be protected from oxidization within its shelf life.

This article provides a simplified testing method for oxygen permeability test of yogurt cup for your reference. The specimens are taken from yogurt cup made from PP.

The testing instrument used is Labthink’s OX2/230 Oxygen Transmission Rate Test System. This instrument uses a coulometric detector to determine the oxygen transmission rate. The specimen is mounted as a sealed semi-barrier between two chambers at ambient atmospheric pressure. One chamber is slowly purged by a stream of nitrogen at a given temperature and relative humidity and the other chamber is purged by a stream of oxygen at the same temperature as the nitrogen stream but may have a different relative humidity than the nitrogen stream. In this case the environment would more closely simulate actual shelf conditions. As oxygen gas permeates through the film into the nitrogen carrier gas, it is transported to the coulometric detector where it produces an electrical current, the magnitude of which is proportional to the amount of oxygen flowing into the detector per unit time. Note: For the package specimens, nitrogen flows inside the package while oxygen flow outside the package.

Figure 1 Yogurt Cups

Before tests, prepare 3 pieces of yogurt cups which have equilibrated at 23℃ and 50%RH for 48 hours.

Then mount the specimens in the following way. Paste the yogurt cup on the test plate with Aradite Rapid Transparent Adhesive. Place the specimen with test plate into the package hood. Cover the specimen with a bag.

Next, add distilled water to adjust the humidity of O₂ and N₂. Turn on the gas supply and adjust the pressure as required.

Switch on the instrument and run the software.

Set test temperature and other test parameters. Start the test. Note: The humidity and the flow rate of carrier gas should be adjusted in testing process.

The test results will be given by the system after the tests are finished.

For more details about OX2/230 Oxygen Transmission Rate Test System, 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.