In the production of canned foods, dark and acidic foods generally interact with the tin and cause color darkening, corrosion and deterioration. In order to prevent this situation, cans are lacquered by applying plastering or spraying methods.

Lacquers are mainly organic coatings based on natural or synthetic resins. Lacquers have two important functions: to protect the can from corrosion and to prevent metal contamination to foodstuffs. In this way, the discoloration of the color and taste of the foodstuff is prevented by lacquering.

The lacquers are generally applied on tinned tin such that 3 – 6 gr / m2. This process is done not only in tin cans but also in aluminum cans.

The most commonly used lacquer varieties are oleoresin. It consists of natural resins and flaxseed oil. It is preferred in canned vegetables, fruits, meat and fish. Lacquer C is a sulfur-resistant lacquer. It is produced by mixing 15 percent zinc oxide to oily artificial lacquers. It is preferred in animal food preserves with high protein content. Vinyl lacquers are flexible and well adherent lacquers and are preferred in the construction of plastering boxes. Suitable for beers. Epoxy phenolic lacquers are flexible and resistant to pressing. It is preferred for lacquering lids in canned milk and egg products and carbonated beverages.

Within the scope of packaging analysis in advanced laboratories, the resistance of the lacquer coating to the solvents at the sterilized temperature is also tested in canned boxes. The lacquer coating needs to be resistant to high temperature solvents and acid in foodstuffs during sterilization. During these tests, the 5 percent solution of organic acids such as acetic acid, tartaric acid or citric acid in foods is placed in the lacquered can, and the box is sterilized. The condition of the lacquer is examined by emptying the can after. Negations such as discoloration or peeling should not be observed.