Oxygen transmission rate
Oxygen transmission rate (OTR) is the speed at which oxygen gas permeates through a material, for example a rigid or flexible plastic film.
OTR is widely used for measuring the barrier properties, or the ability to resist the permeation of oxygen, of different packaging materials, because oxygen is a major cause of food spoilage of packaged goods.
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Oxygen transmission rate (OTR) is a method with which the transmission rate of oxygen gas through a material can be measured. OTR is most commonly used for determining the barrier properties of packaging materials. These properties significantly affect the preservation of food and cosmetics along with pharmaceutical and other products. In addition to water vapor, oxygen mostly causes the reactions associated with food spoilage and thus affects the shelf life of a packaged product. Oxidative degradation can affect the color, flavor, and microbial stability of foods like coffee, chocolate, cheese, meat and retorted products. This is why the oxygen transmission rate along with water vapor transmission rate (WVTR) is a key property of a material which affects the shelf life of food packages.
Prevention of oxidative degradation
Removing the air from the package (vacuum packaging) or replacing the air with nitrogen or carbon dioxide (modified atmosphere packaging, MAP) are common ways to prevent oxygen-induced reactions and maintain the quality of the product during its shelf life. The success of these two approaches depends on the packaging material’s ability to act as a barrier, that is its ability to overcome the natural flow of oxygen created by the differences in the partial pressures of oxygen between the inside of the package (0-2%) and the outside of the package (21%).
Measurement details and methods
Oxygen transmission rate, the steady state rate at which oxygen gas can permeate through a film, is expressed as a mass of oxygen that permeates a given area in a one-day period: g/(m2⋅24 h). Material permeability is affected by the thickness of the material but also by certain environmental factors, such as relative humidity (RH) and temperature. Oxygen transmission rate can be measured in a range of different standard temperatures and relative humidities, such as 23 °C and 0% RH. The typical testing area can be chosen to suit the size of the sample. The oxygen barrier capability of the material is defined with the help of OTR: the material can be able to resist the permeation of oxygen well (high barrier properties) or poorly (low barrier properties).
Several methods can be applied when determining the transmission rate of a material to a certain gas. Methods that use oxygen detectors are most applied in the examination of food packages, because in that case a low permeability needs to be determined with high sensitivity. The used sensor only detects the molecules of the gas of interest, in which case it does not take the rest of the atmospheric gases in the surroundings into account. When starting the OTR analysis, the temperature and relative humidity (dry, normal or moist) where the test is performed have to be chosen based on the predicted storage conditions of the product. The selection of the test conditions is very important because the result of the measurement varies depending on the temperature and humidity of the environment.
In coulometric OTR, a barrier film of the material of interest is sealed between the two chambers of the OTR machine. One of these chambers contains oxygen and the other one lacks it. A coulometric sensor measures the oxygen that is transmitted through the barrier film from a chamber to another and thus determines the oxygen transmission rate and permeability of the material.
Oxygen transmission rate can be determined for flexible barrier materials used in the packaging of various products or in industrial applications: plastic films and sheetings used in rigid and semi-rigid packages are suitable sample materials. The barrier properties of a material can usually be improved with coatings. The properties of coated special films such as foil or metalized PET, CPP, EVOH, AlOx or SiOx can be measured with OTR.
Suitable sample matrices
- Packages of for example food, cosmetics and pharmaceuticals
- Rigid and semi-rigid packages
- Plastic films and sheetings
- Coated papers
- Aluminium foils
- Metalized films
- Non-coated films
Ideal uses of OTR
- Measuring the barrier properties of packaging materials against oxygen
- Industrial applications
- Product development and quality control
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Frequently asked questions
OTR is most commonly used for determining the barrier properties of packaging materials for different products against oxygen in order to help estimating their shelf lives. OTR helps to design packaging materials with characteristics optimized for unique demands of a certain product. Improvement of product quality and shelf life is possible by optimizing oxygen transmission rates of the packaging materials based on the results of OTR analysis. Adjusting of copolymer ratios, plasticizer content, and polymerization processes with the help of OTR enables efficient product development also in industrial applications.
Relative humidity (RH) can have a big impact on the barrier properties of certain films, which is why OTR measurements are usually done under dry conditions. For example the oxygen transmission rate of EVOH increases drastically when RH exceeds 75%. The thickness of the film and the temperature of the environment are also needed to take into account, because they can affect the results for their part.
The barrier materials used in OTR must often be flexible, rigid and have a smooth surface.
Flexible barrier materials of rigid packages are suitable for the analysis. Samples can be for example plastic films and sheetings, laminates, coated papers, aluminium foils or metalized films. Samples need to have smooth surfaces in order to achieve a tight seal between the two chambers of the OTR machine.
Measurlabs offers a variety of laboratory analyses for product developers and quality managers. We perform some of the analyses in our own lab, but mostly we outsource them to carefully selected partner laboratories. This way we can send each sample to the lab that is best suited for the purpose, and offer high-quality analyses with more than a thousand different methods to our clients.
When you contact us through our contact form or by email, one of our specialists will take ownership of your case and answer your query. You get an offer with all the necessary details about the analysis, and can send your samples to the indicated address. We will then take care of sending your samples to the correct laboratories and write a clear report on the results for you.
Samples are usually delivered to our laboratory via courier. Contact us for further details before sending samples.
Analysing the oxygen barrier properties with the help of oxygen transmission rate (OTR) is an easy way to determine the quality of your packaging materials. Measur offers high-quality OTR services through our wide network of reliable laboratories.