Ideally, we recommend a minimum of 15cc of available headspace. This allows the sample pump to run for several seconds (drawing 5cc/sec) and get a complete reading. However, there are many packages that have less headspace available, and need to be analyzed in a different way.
When deciding on a sampling method, an important consideration is how much headspace, or available space in the package there is – not including your product.
This is far more critical in a rigid package than it is in a flexible package, and here’s why:
When analyzing a rigid package or container, the pressure of the inside of the package will decrease in direct proportion to how much of the gas is removed (assuming there are no leaks). In other words, if you have a 100cc container, and you remove 15cc of the atmosphere in the container, your oxygen readings will be low by 15%. This is because our analyzers use an internal pump to draw in sample, and the flow is only allowed to travel in one direction – out.
You could correct for this discrepancy, but sampling this way is not recommended. The long term durability of the analyzer, specifically the sensor and pump, can be impacted by pulling on a vacuum.
There are several clever methods around this problem – one is to draw your sample out of your container using a syringe with a special stopcock mechanism. By allowing the syringe to “collapse” to atmospheric pressure, you could then inject the contents of the syringe into our Model Q20 Portable Series, the Model Q30 Benchtop Series, or any of our other package analyzers.
Our full line of package analyzers is located here: https://www.quantekinstruments.com/product-category/food-package-testing/
The other method (and this will only work with a semi-rigid container – imagine a 2L soda bottle) is to connect the bottle to the analyzer and squeeze it. All of our analyzers will react to whatever gas is in the sensor, whether the pump is actuated or not.
No matter what your package or product is, we have detailed documentation, and many available accessories to assist you in measuring the residual oxygen content, or CO2 concentration, in your package.
Here’s a good example of a video demonstrating a very unique sampling method we designed for a particular customer. They did not have the vacuum issue as their package was flexible, but due to the nature of their product, and the limited headspace, usage of the pump was not possible: