Preventing Micro Leaks In Bakery And Confectionery Modified Atmosphere Packaging

Modern leak testing solutions help producers of bakery products prevent even micro leaks and thus, guarantee fresh products to their customers. By Alexander Kampschulte, Head of Marketing & Communications, WITT-Gasetechnik GmbH & Co KG.

Packing under modified atmospheres has established itself as the standard in the food industry. Even more than that: this proven method is becoming more and more important worldwide. Particularly for bakery products, this packaging technology offers several benefits, but it can only fulfil its task efficiently if the packages are really leak-tight. Modern leak testing solutions help producers of bakery products prevent even micro leaks and thus, guarantee fresh products to their customers.

The modified atmosphere in the package counteracts the growth of microbiological organisms and bio-chemical reactions and the consequent spoilage of the goods. However, this modern packaging technique makes comparatively high demands on the packaging process. Most notably, the sealing process contains various sources of error which can lead to leaks: defective temperature or pressure distribution, improper sealing tool arrangement, impure or worn out tools as well as seal contaminations.

Even worse, defective material can lead to undetected serial leaks.

Water-Based Sample Test As An Entry Solution

The easiest solution is a water-based sample test. This method is very common and popular because it’s simple but effective. The test product is placed into an acryl chamber filled with water. The test device evacuates the air space in the chamber above so that a vacuum results. If the product is leaking, air or filling gas will bubble out. This method is not only extremely reliable but also offers a valuable additional benefit: the leak can be localised precisely. This makes this simple test unique.

The system is also economical. Installation and commissioning are easy, without any need for calibration or special training. To produce the vacuum, some devices use an electric vacuum pump. Products like LEAK-MASTER EASY from WITT are easier and safer as they use just water and compressed air, without any need for an electrical connection.

On the other hand, there are some disadvantages. The water-based sample test is not the fastest possible test and is has limits when it comes to micro leaks. And, of course, it’s a test that depends on the human tester. To achieve faster and standardised test procedures, it’s possible to combine devices like the EASY with an electronic control. As a result, the results will get documented automatically.

Pressure Difference As A Special Option

The pressure differential test depends on air or gas inside the package. The product is placed in a chamber and the chamber is evacuated. If there is a leak, gas will escape from the package. In contrast to the trace gas method, the sensor does not directly detect the gas, but only a change in pressure in the test chamber.

The method allows standardised test procedures and, of course, digital documentation. There are some devices in the market that are based on the pressure differential test but up to now, this is not the preferred solution for many food producers. This solution is not that flexible in terms of different packaging forms and sizes and has limits regarding micro leaks. In addition, these solutions are very expensive compared to others. Lastly, this method can be used only for sample leak testing.

Leak Testing With Trace Gas

This solution is different with methods that rely on trace gas to detect leaks. Besides the classic water bath, these variants are widely used to check bakery packaging as a sample test or as an inline test.

Sample test equipment usually works with CO₂ sensors. The test product is placed in a test chamber. The chamber is then evacuated via a vacuum pump. In the event of a leak, gas flows out of the packaging.

Highly sensitive gas sensors detect even the smallest leaks in this way. The measurement takes place within a few seconds, whereby the packaging is not damaged. All test data can usually be captured and saved and exported for documentation purposes. The method allows a standardised test process independent of the tester.

Inline Leak Testing For 100 Percent Safety

Only leak testing packages completely through the final inspection offers genuine safety. There is a choice of solutions with CO₂, hydrogen or helium. CO₂ is often used as it is already included in most inert gas packaging. Helium and hydrogen offer advantages in inline testing regarding speed and leak size. But these gases are not a genuine part of the modified atmosphere; they are expensive and require additional technical equipment. Although solutions with helium and hydrogen are available at the market, they have not really been successful.

Thus, the standard trace gas has become CO₂. It’s easier, cheaper and absolutely reliable. Also working with this gas, the systems detect even the smallest of leaks. Especially the leak sizes that are relevant to most food producers.

When using CO2, there are two different technologies available: putting the packaging under pressure with a kind of role, or placing the packing inside a vacuum chamber. The role allows higher speed and is useful for testing single packages—but it can’t be used for every kind of packaging because the role stresses the packaging and can destroy it. Another big disadvantage: high speed testing is only possible when checking for bigger leaks not micro leaks.

This is possible with vacuum chamber machines. They work exactly like the sample test devices: the product is placed into a chamber and a vacuum is generated. If the packaging is leaky, gas will escape and be detected by CO₂ sensors. The fastest machine on the market is the MAPMAX from WITT offering a speed of up to 15 cycles per minute and a measuring range between 0 and 5,000 ppm.

If a product is leaky, the system can directly trigger a pusher to sort out a faulty package. Since testing of boxes and complete shipping cases is also possible, insufficient speed is usually not an obstacle anymore. The LEAK-MASTER EASY has already proven successful in numerous trans-European installations and is very often used for quality control of bread.

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