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Heat Seal Strength Test of Frozen Food Package

Dec 20,2019

Source: Linktesting Instruments Co., Ltd

By freezing the food quickly at an ultra-low temperature, it can be preserved from the time it is prepared to the time it is eaten. Frozen food slows down decomposition by turning residual moisture into ice, inhibiting the growth of most bacterial species. No extra preservatives are required because microorganisms do not grow when the temperature of the food is below −9.5 °C (15 °F), which is sufficient on its own in preventing food spoilage.

Today there are multiple options for packaging frozen foods: boxes, cartons, bags, pouches, Boil-in-Bags, lidded trays and pans, crystallized PET trays, and composite and plastic cans.

No matter which kind of form of the frozen food package is, it must maintain its integrity throughout machine filling, sealing, freezing, storage, transportation, thawing and often cooking. 

In order to meet such requirements, the seal strength of the sealing edges of frozen food package must be proper. To be specific, the seal strength cannot be too high (even higher than the compounding strength), otherwise much difficulties will be caused when opening the package. On the other hand, the seal strength should be adequate, otherwise the package may pop open or break because of internal and external compression especially during transportation. As a result, the quality of the food may be compromised or even worse the human health can be threatened.

In this article, plastic composite package is taken as an example to elaborate on the heat seal strength test of frozen food package. Link Testing LTS-05 Auto Tensile Tester is used as the testing instrument for heat seal strength of plastic composite frozen food package specimens.

Tensile Tester LTS-05

The seal strength tests can be performed according to the following procedures.

  • Prepare sealed test specimens for testing. Edges shall be clean-cut and perpendicular to the direction of seal. The width of the specimen is 15mm and the developed length of the specimen is 100mm.
  • Clamp each leg of the test specimen in the tensile testing instrument. The sealed area of the specimen shall be approximately equidistant between the sample grips.
  • Set test parameters including specimen width and test speed, etc.
  • Start test. The force values will be recorded automatically in the testing process.

For more details about LTS-05 Auto Tensile Tester, please visit

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