Tinplate has good barrier properties and processing properties, and is often used in the packaging of moon cakes, chocolate, tea, coffee, biscuits, milk powder, fish, luncheon meat, beverages and other foods. The core material of the tinplate is iron and is plated with tin on the surface. Iron is active and easily reacts with oxygen and food to cause corrosion of the package, resulting in damage to the barrier and integrity of the package. Although tinplate is tin-plated on the surface, due to the high cost of tin, the amount of tin plating is generally not high enough to resist the invasion of the contents. Therefore, in addition to fruits and vegetables that are less corrosive and have reduction requirements, tinplate used in most foods requires an internal coating.
Coatings are organic compounds and are mainly composed of oils, resins, pigments, plasticizers, thinners and other additives. Among them, oil and resin are the main film-forming substances, and pigments and plasticizers are auxiliary film-forming substances. Diluent and the like are used for the dilution of the resin or pigment to facilitate the coating of the coating. The solvent is a volatile substance and should be completely volatilized after processing. However, in actual production and use, the metal tinplate can protect the contents from environmental pollution and the various substances contained in the inner surface coating of the inner surface of the metal tinplate, such as free phenol, Free formaldehyde and other monomers, when the amount of migration has accumulated to a certain extent, will endanger food safety and pose a threat to human health. It is therefore necessary to test the quality of the material that the tinplate coating migrates into the food.