Active polyvalent packaging based on environmentally friendly fibre material
The ACTIPOLY project (May 1st, 2015 until October 31st, 217) had a goal to develop a thermo formable, fiber based material for compostable trays for fresh food. This tray was also provided with an adequate barrier against oxygen and vapour, as well as an antimicrobial coating. The project was an ERA-NET CORNET project, with partners from 4 European regions, Germany, Poland, Wallonia and Flanders.
Through different chemical modifications a thermoplastic celluloses matrix was developed, which led to individual thermoplastic fibers. From that, sheets were produced that were then thermoformed into trays. This thermos forming process was successful. Tensile tests proved that the stretch at breaking point was more than 35%, which is sufficient for this process.
A great deal of formulations was tested to be applied as thermo formable barrier coating, this to give sufficient gas and water barrier to the concept. During the project it became clear that the barrier characteristics for water, oxygen, as well as for fat and oil decreased with 20% or more. Adding plasticizers to increase the elasticity of the coatings did not show an improvement. As an alternative, a spray coating technique was applied after thermo forming the tray. This was evaluated as the best option.
Techniques were studied to apply an antimicrobial coating in addition to a barrier coating. The performance of super hydrophobic coatings was lower than this of the more classic antimicrobial formulations where an active ingredient is mixed in a matrix. The most efficient formulas were obtained by taking methylcelluloses as matrix and PSP (plant extract) – polylysine as active ingredient.
At the level of the top foil, antimicrobial foils were developed by means of a triple layer structure of PLA (Polylactic Acid) in which zinc oxide (ZnO) particles are present. Further surface treatments led to ZnO particles that became available at the surface of the foil. This foil showed good antimicrobial characteristics, as well as good seal characteristics. However, the oxygen and water barrier generally were rather low.
The final barrier characteristics of the tray/foil combination are in the same range as these of the currently used materials for packing fresh meat, one of the selected products for Actipoly. From the conservation tests on lab scale with fresh meat in the Actipoly tray/foil the performance appeared to be similar to the conventional packaging materials at the level of microbiological shelf life.
During the project it was successfully proven that the concept of these new fiber based thermo formable packaging materials works and that it can be applied for packing foods. Before having a commercial product, a few improvements still need to be made through further research. The production costs for making thermos formable fibres currently appear to be too high. This also led to having too few trays available to perform a conservation test on industrial scale. Besides that, the uniformity and drying time of the coatings was not optimal and the coating was sensitive to damages while piling the trays.
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