Modified atmosphere packaging (MAP) is nothing new. The technology of substituting the atmospheric air inside the package with a protective gas mix to extend the shelf-life of fresh food products – including meat – has been around for years and no one argues the benefits. Retailers enjoy the longer shelf-life and the more appealing product presentation they obtain from using MAP. And, consumers appreciate fresher products that don’t require the addition of preservatives.

With so much riding on the MAP technology, many suppliers are looking for quality assurance. When a modified atmosphere package leaks, there can be several negative effects on product quality – a loss of flavor or taste, or a change in texture or color due to spoilage can result from microorganisms on the product. Along with product spoilage are the possibilities of health risks and recalls.

According to Alpharetta, Ga.-based Witt Gas Controls North America, there are many sources of errors that can lead to leaks including wrong temperature or pressure, unsuitable tool design, contaminated or worn tools and sealing contamination, in addition to faulty material, which could cause undiscovered continuous leaks.

In-line package-leak detection systems can offer MAP customers a quality control “freshness guarantee.” And this guarantee can provide a competitive advantage.

System selection

After deciding to incorporate a package-leak detection system into the production process, the next step is to decide which method to use. There are many pros and cons to consider. The selection of the most appropriate leak test depends on many factors. An in-line leak-testing system can be incorporated into the packaging line or sample testing can be performed.

David Bell, president of Witt Gas Controls North America, says in-line testing is suitable for, “any processor using MAP with CO2 or CO2 mixtures for their products, as packages with modified atmosphere promise fresh, appealing and high-quality goods without using preservatives. In-line testing offers 100-percent leak detection, which may be critical for some processors.”

In-line testing, however, is limited to a packaging range of eight to 16 packages per minute per machine. Another option is sample testing using the “bubble” test. “The bubble test is one of the oldest and most intuitive leak tests,” Bell says. “In this method, the package is placed into a chamber filled with water and the package inflates and leaks become visible as a stream of bubbles.”

Important factors to consider when choosing a leak- detection method include determining if trace gases were used during the MAP process. If there aren’t any trace gases, then the water vacuum bath (bubble test) is probably the only option.

In using the bubble test, the pros include the low initial costs and localization of the leak, Bell explains. The cons include limits when detecting micro-leaks; possibility of human error; destruction to the package (it can’t be sold after); and no digital documentation for quality assurance.

If there are trace gases used in the MAP process, then there are specific devices designed for those systems. With trace gases there are both sample and in-line detection systems available. According to Witt Gas Controls, in either case, “the test product is placed in a test chamber, and the chamber is evacuated. In the event of a leak, gas flows from the modified-atmosphere package. Highly sensitive gas sensors detect even the smallest leaks with measurements taken within a few seconds.”

An alternative method doesn’t detect the trace gases when in the chamber, but rather the change in pressure in the test chamber. “This method can only be used for sample leak testing, and in-line automation is not possible,” Bell says.

Bell explains the leak-detection process using a test chamber: “Chamber sizes can vary for either process; the chamber size is determined by the size of the sample[s] to be tested, which may be only the package or can be the carton which contains many packages. Various chamber sizes are offered for either method. As both methods are manual processes, the number of packages that can be tested is below five per minute for most products. With the in-line CO2 leak detection method, the number of test cycles can be as high as 16 per minute depending on size of package and leak detection parameters.”

Advantages of these methods include the package will not be damaged, and all leak-test data, (e.g. date, time, name, product and tester) is recorded and digitally archived for documentation purposes.

Bell says the pros of using a leak-detection system when trace gases are present include: short measurement time; detection of micro-leaks; non-destructive to the package; in-line testing with 100-percent control; and full documentation for quality assurance. The con is no localization of the leak.

Adding package leak-detection systems can be incorporated into a plant’s Hazard Analysis and Critical Control Point (HACCP) program. Every step of the production and packaging process must be part of a plant’s HACCP program. The packaging part of the production process – especially when MAP is used – should be outlined as a critical control point – more specifically “a step or procedure in a food-manufacturing process at which control can be applied and, as a result, a food-safety hazard can be prevented, eliminated or reduced to an acceptable level.”

In this case, leaks can occur during the MAP process. HACCP involves establishing critical control point monitoring requirements. Leak testing of food packaging is a suitable method to monitor critical control points and to ensure food safety. The next HACCP step is to establish corrective actions (these are actions to be taken when monitoring indicates a deviation from an established critical limit). If packaging leaks are detected, then corrections can be made.

When leaks are detected, depending on the tolerances and limits set up by the plant’s quality assurance department, more products may be tested. When products end up with package leaks, the product is usually disposed of. However, disposing of a small amount of product here and there can save money from product spoilage or potential recalls in the long run, the costs of which are considerably higher.