Cleaner coatings for food cans
Cleaner barrier coatings for metal food cans were the focus of a three-year study funded by the Department for Environment, Food and Rural Affairs.
The project, ‘New technologies and chemistries for food can coatings', was managed by Julian Stocker from Heinz UK, based in Cheltenham. The goal was to study coating migration into food and how it can be minimised.
‘Present coatings are safe and comply with extensive international regulations,' says Stocker. ‘But for food manufacturers this is not enough, their target must be zero contamination of food by the packaging.'
Paul Stenson, Chief Technology Officer at Valspar, an international coatings manufacturer that collaborated on the project, adds, ‘There has been continuing interest from consumer advocacy groups to understand the exact migration characteristics of coatings. This is also driven by the new REACH legislation, which affects the chemical industry in Europe'.
The researchers conducted kinetic tests on chemical migration from epoxy phenolic, epoxy anhydride, organosol and polyester polyurethane coatings. An approach using liquid chromatography time-of-flight mass spectrometry was developed to give more accurate information on the mass of individual molecules.
Key parameters influencing the migration of chemicals into cans are - the level of wax lubricatIon, the coating's age, curing times, film thickness and food temperature. Each factor is dependent on the requirements of the food being packaged.
Valspar has now commercially released faster-curing epoxy phenolic and polyester polyurethane coatings for three-piece food can interiors, and is continuing to develop solvent and water-based coatings. Heinz has also adopted a new coating for some of its tins, though Stocker could not reveal details of its composition.