A Guide to 6 Leak Testing Methods for Food Packaging

Improving the integrity of the package seal is once again a priority due to recent supply and demand issues which include the following six reasons:

  1. Obtain consistent waterproofing layers;
  2. Adjust packaging layers to allow recycling;
  3. Other qualified suppliers or packaging materials;
  4. Faster production line speeds to meet demand;
  5. Increase in electronic commerce;
  6. Use of alternative distribution channels.

Maintaining the integrity of package seals is a food safety and quality issue. Quality Control Standard operating procedures for measuring seals at production start-up and shift changes are determined based on the integrity of the seals required, labor and equipment variability sealing and consistency of packaging materials.

In terms of food safety, the integrity of the sealing film is often an essential point for risk analysis and risk control (HACCP). For example, small leaks in the seal area can expose the product to cocci (1 µm) or rod-shaped (0.5 µm x 10 µm) bacteria, and larger leaks can expose the product to droplets. of contaminated water which are of a much larger order of magnitude than bacteria.

Six standard methods for testing seals can be modified to meet the needs of a specific package. These are…

  1. Gas leak test: The migration of helium through a sealed package is measured by mass spectrophotometer. Helium is used because of its low presence in the atmosphere, its non-explosive nature and because it is chemically inert. As a result, ultra-fine leaks that are seven orders of magnitude smaller than other test methods can be detected. the Dansensor LeakMatic II is an online bypass testing system.
  2. Ultrasonic leak test: The leaks are exposed to ultrasound and emit a modified frequency relative to the rest of the seal area so that the specific location of the leak is determined. This method has wide application and is often used to detect the presence of contaminants in the seal area.
  3. Vacuum disintegration test: When a sample package is placed under vacuum, leaks are detected as the vacuum decreases in the area surrounding the package. Infon Contura S400 Leak Tester is an example of a vacuum decay tester.
  4. Bubble emission test: The internal pressure that the seals can withstand is measured using a vacuum. When a vacuum is applied, the packages swell due to the pressure difference and leaks are apparent when the operator sees air bubbles coming out of a sample submerged in water. Modified ASTM bubble emission methods are common because the equipment required for the modified method – air hose, needle and water – is generally available.
  5. Dye penetration test: An operator applies dye to one side of the seal area, then examines the other side of the seal to assess whether the dye has transferred through the seal. Detectable leaks are six orders of magnitude larger than most permients such as oxygen, carbon dioxide, nitrogen, so this method is not useful for detecting small leaks in modified atmosphere packaging, gas packaging or packaging requiring an airtight seal for the shelf life of the product.
  6. Seal strength test: The maximum force required to pull apart a 1 inch sealed package section is measured. Test results are often affected by the mechanical properties of the packaging material.

Claire Sand, PhD, has over 30 years of experience in industry and academia. She owns Packaging technology and research and Gazelle Mobile Packaging and is an adjunct professor, CalPoly, Michigan State University, and the University of Minnesota. His email is [email protected]

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