How to detect leaks 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. In this blogpost, we have a look at why we test for leaks of the gases in the way most companies do today. Obviously the manufacturer and the retailer don’t want angry customers if they find that their MAP packaged ham has gone off before the sell-by date because there were leaks in the package.
So let’s say you’ve packaged your product and made sure the headspace mixture is correct. Everyone is happy. However, suppose there is even a tiny leak in the package because the seal has not formed properly.
MAP Equipment Expert
|“Remember, there is 20.9 per cent oxygen in the air that we breathe,” says Bob Olayo, a MAP equipment expert with FF Instrumentation, based in Christchurch, New Zealand. “If you have only 1 per cent oxygen in your package and there is a leak, then the laws of physics say that oxygen will get into the package quickly.
The oxygen will want to reach 20.9 per cent in the package as well. The consequence is that the food will go bad quickly since it’s not protected in the modified atmosphere anymore.”
So testing for leaks is necessary. The simplest and least expensive option is to use a water bath. Here the operator simply puts the package in water. The air above the water is sucked out. This creates a vacuum, which draws any gas from the package out through the leak. The leak will show up as bubbles.
There are many problems with this approach, though:
- Bubbles can form from trapped air on the surface of the package. The operator may find it tricky to tell the difference between this and a bubble coming from a small leak.
- It can depend on who is actually doing the test: I might spot a leak but you might not.
- Dunking your packet in water means that you will have to throw out the packaging, and maybe even the product.
- It is not a great idea to introduce water into a food processing area because of hygiene reasons.
- The water bath must be clean, something that is often neglected.
A better solution is for a non-destructive system which directly detects any leaking gas. These can be either off-line or in-line. Here, the operator places the package in a sealed chamber from which the air is drawn out. If there is a leak in the package, the gas in the package will be pulled out into the chamber. A sensor will pick up any carbon dioxide that leaks out from the package – carbon dioxide is a commonly used MAP gas. An off-line leak detector is operated manually with the operator selecting packages at random.
In-line leak detectors offer a fail-safe system. The detector is integral to the packaging line and every package is tested before it comes off the line. “This gives you gold standard quality assurance,” notes Bob. “You don’t need any water and you don’t generate any waste. An excellent solution.”