Effect of the degree of muscle oxidation on sticking and degradation of polyethylene terephthalate (PET) layers in electrolytic chromium coated steels

The sticking of postmortem salmon to the container wall surface protected by polyethylene terephthalate (PET) polymer was evaluated. The study focused on the effects of biochemical changes of postmortem salmon on the coating and how muscle degradation inside the food can, resulting from the thermal treatment and storage, favor sticking to the food container. The experimental design consisted of a set of manufactured food cans stored for up to fourteen months which were submitted to chemical and physical tests of food-contact canning to evaluate the sticking, and to treatment with urea solution to minimize the amount of muscle residues. The characterization of changes in the multilayer was performed by scanning electron microscopy and atomic force microscopy. The degradation of the muscle–polymer system was evaluated by Fourier transform infrared, Raman, and nuclear magnetic resonance analyses. The results showed the existence of denatured muscle proteins firmly sticking to the PET surface over time and the adverse effects of urea leading to chemical changes and molecular rearrangements in the polymer coating altering its functionality as a protective layer in canned salmon, limiting thereby the potential use of PET as a recyclable input in other applications.