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Pros and Cons for In-line and Headspace Analysers in MAP

The Difference Between In-line Analysers and Headspace Analysers in Modified Atmosphere Packaging

The basic concept of Modified Atmosphere Packaging, or MAP, is pretty straightforward. You package your product – meat, cheese or pizza for example – in a sealed packet containing a mixture of gases. These will extend the shelf life of the product and at the same time make sure it looks tasty and enticing to the shopper.

Usually this means flushing most of the oxygen out of the package with a blend of gases such as nitrogen and carbon dioxide.

Now, the concept is easy, but getting it right can be tricky. And it is vital that manufacturers do get it right. A busy housewife with kids clamouring for their dinner does not want to find that the ham has gone off before the sell-by date!

Quality control and quality assurance are the key watchwords in MAP. This article looks at the ways that food processors can check that the gas in the package has the correct mix, and if the package has any leaks. These are two of the main junctions in the MAP process where quality control and quality assurance are central.


Headspace Analysers

Bob Olayo is a MAP equipment expert with mätt solution (formerly FF Instrumentation Ltd.), based in Christchurch, New Zealand. “First of all the mixture inside the package must be the correct one,” says Bob. “I do a lot of presentations, and I always emphasise that in MAP you must know where you are starting from: And that is that the air that we breathe contains 20.9 per cent oxygen – obviously much more than we have in MAP products.”

Bob from mätt solution

Bob Olayo MAP Equipment Expert mätt solution


The most straightforward and inexpensive way to test the gas in the package – the headspace gas – is to use a headspace analyser. These can be battery-operated portable devices, or else mains-operated desktop machines.

Here, the operator removes a package from the line at intervals – every 15 or 30 minutes, say – and inserts a probe into the package to measure the oxygen level. The advantage of this system is that it is quick and easy. Also the factory can have just one headspace analyser for several packaging lines.

There are drawbacks, however:

  • The operator must remember to do the test at the appropriate interval. We are all human – people forget!  
  • The test is destructive – it ruins the packaging, which then has to be thrown out. This means wasted packaging material and wasted gas. Remember every 15 min in 24 hours, 365 days a year per line! 
  • If you do find a problem then you have to go back through the packages since the last test to find out where the problem first occurred. That could be half an hour’s worth of production. With the high speed of modern packaging machines that could equal a lot of packets.
  • In short: It’s wasteful and time-consuming!

Quality Control to Quality Assurance: the Best Approach

The alternative to manual testing is to have an in-line gas analyser. This is an instrument that keeps tabs on the gas mixture inside the packaging chamber. So, the in-line gas analyser will automatically shut down the line if any mixtures falls outside the pre-set limits. This eliminates the need for people testing, and thus eliminates human error.

This also means that there is no waste and the system pretty much runs itself. Some in-line gas analysers also have a smart ’gas save’ function. This is when the analyser ‘knows’ how much of each gas is coming through. It intelligently controls the flow of the gases to make sure they stay at the right level. Often with manual systems the operator takes a ‘better safe than sorry’ approach and sets the flow rate extra high. This is to be certain that all the oxygen is flushed out. Unfortunately this means that more gas is used than is needed. Again a waste of gas and a waste of money. Read more about avoiding waste of manual testing in this blogpost.

And while you need one in-line gas analyser for each packaging line – as opposed to a headspace analyser that can work across lines – there are many advantages: 

  • Cost savings from reduced gas consumption.
  • Zero packaging waste.
  • Minimal labour costs.
  • An in-line analyser soon pays for itself.

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