Protein-based edible films have received consideration attention in recent years because of their advantages, including their use as edible packaging materials, over the synthetic films. In addition, protein-based edible films can also be used for the individual packaging of small portions of food, particularly products that are not currently individually packaged for practical reasons, such as beans, nuts and cashew nuts. The common protein-based edible films include whey protein film, wheat gluten film, soy protein film, corn zein film and peanut protein film, etc.

In addition, protein-based edible films can be applied inside heterogeneous foods at the interfaces between different layers of components. They can be tailored to prevent the deterioration of inter-component moisture and solute migration in foods such as pizzas, pies and candies. Moreover, protein-based edible films can function as carriers for antimicrobial and antioxidant agents. Through a similar application they also can be used at the surface of food to control the diffusion rate of preservative substances from the surface to the interior of the food.

Another possible application for protein-based edible films could be their use in multilayer food packaging materials together with nonedible films. In this case, the protein-based edible films would be the internal layers in direct contact with food materials. Through functions relating to mechanical and barrier properties, protein-based edible films may be able to substitute synthetic polymer films. This article provides a test method of oxygen barrier property of protein-based edible film for your reference, which may be helpful to those food manufacturers in quality control of protein-based edible films before use. We did the tests with Labthink’s C230H Oxygen Transmission Rate Test System and the test specimens are wheat gluten films.

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. C230H Oxygen Transmission Rate Test System

The tests can be performed according to the following procedures.

(1)    Cut three pieces of specimens from the provided sample material with sample cutter. Then clamp the specimens in the three test cells respectively.

(2)    Set test temperature, humidity, specimen name, thickness and other parameters. Then click Start Test to start the test. In order to avoid shattering of the specimens, the test temperature and humidity shall be set at 23℃ and 60%RH.

(3)    Adjust the flow rate until the humidity inside the test cell reaches the preset value.

(4)    When the tests are finished, the instrument will display the results automatically.

(5)    Finally purge the gas circuit and power off the instrument.

For more details about C230H 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.