Sven Sängerlaub et al. looked at oxygen absorption in different multilayer film structures including an iron-based OS under defined gas atmospheres.
Defects in the sealing layer of films, below the typical detection limit of 10 microns for standard leak testers, could be solved by the addition of an OS layer to provide extended protection.
Oxygen scavengers (OS) are small sachets or self adhesive labels that are placed inside modified atmosphere packs to help extend product life and improve product appearance.
Sealing defect
The researchers identified sealing defects such as damaged barrier layers at the sealing zone and pinholes in the sealing layer as a weak point in barrier packages as they enable the permeation and possible increased amounts of oxygen into the package.
“These defective packages need to be filtered out by quality control procedures to avoid consumer complaints due to oxidative food deterioration,” wrote the researchers.
“An effective option to compensate smaller pinholes up to a diameter of 10 microns is the application of O2 scavengers (OSs).
“OS incorporated in packaging materials, for example, as an O2 absorbing layer of a multilayer film structure, could protect foods from oxidative spoilage process and restrain the growth of aerobic microorganisms.”
Measurement cells were covered with plastic films of defined oxygen permeability to simulate conditions in a food package during storage with pinhole defect sizes of 10 and 17 microns.
The results indicated that the OS film structures applied could only compensate for a defect size of 10 microns in the sealing layer but higher humidity accelerates the activation of the scavenger.
OS have to be incorporated in multilayer structures with the base layer providing the mechanical strength, the barrier layer reducing the O2 permeation rate of the film, the oxygen scavenging layer absorbing residual O2 in the package and the sealing layer providing sealing properties.
By testing salami when it was fresh, originally packaged and samples with and without the scavenger they found that the OS is able to compensate the sealing defects and preserves the colour of the snack product.
Conclusions
The researchers concluded: “The present study shows that gas atmosphere conditions in a food package could successfully be simulated via measurement cell systems covered by a plastic film of defined O2 permeability.
“The investigated film structures, more precisely the respective thicknesses of the OS and sealing layers, significantly influence the effectiveness of OS multilayer films.
“The investigated scavenger films were able to compensate a simulated O2 permeation through 10-micron pinholes but not through 17-micron defects.
“The combination of integrating an OS in packaging materials with leak detection along the filling line could be recommended to provide enhanced product safety for products of high O2 sensitivity.”
Source: Wiley: Journal of Packaging Technology and Science
Published online ahead of print, doi: 10.1002/pts.1962
