(enamel) Lacquer is a liquid whose main component is Oleoresinus resin or compounds of vinyl (vinyl)
or epoxy or phenolic or polyester and solvent
– Prevents discoloration of food: Dissolved metal mixes with food.
– Prevent food discoloration
– Prevents chemical reactions between metal and food. that may cause corrosion of the canister or the generation of hydrogen gas inside the canistertype of lacquer
Lacquer standard for use with food containers in the Thai Industrial Standard entitled “Lacquer for use with food containers” (TIS 735).
There are two types of lacquers used for food cans:
(1) Type 1 lacquer for coating cans that have undergone thermal processing, which is further subdivided into 3 types:
- Acid-resistant type for canned food with high acidity (acid canned food)
- Sulfur resistant type For canned food with high sulfur content
- General type For canned food other than acid and sulfur resistant type.
(2) Type 2 Lacquer for coating cans that have not undergone heat treatment.
Types of lacquers used to coat cans
Commonly known lacquers for canning coatings are:
- Oleoresinus Lacquer Although it is currently being replaced by epoxy-phenolic lacquers. (epoxy phenolic) But it is still sometimes used in the United States for coating cans of fruit and vegetable products. part in Europe Epoxy-phenolic lacquers are often used as replacements more than oleoresinus lacquers. It has the property of preventing black staining of tin. Sulfides are not very good. Therefore, at present, zinc oxide is added.(ZnO) into this type of lacquer to help preserve the color The nature of some fruit and vegetable products containing anthocyanins. (anthocyanin) such as berries, beets, red cabbage, etc., as well as for protein-containing foods.such as corn, dried beans Duck and chicken meat, seafood, etc.
- vinyl lacquer The unique property of this type of lacquer is High adhesion and flexibility But there is a disadvantage is that it cannot be tolerated. heat to sterilize However, because this type of lacquer is free from smell and taste. Therefore, it is commonly used as a second layer coating on cans of beer, wine, soft drinks, desserts, and dry foods. And pharmaceutical products can be used to coat both steel and aluminum. In general, vinyl lacquer is often mixed with alkyd. (alkyd) phenolic and epoxy to provide the desired properties. want to use only
- Phenolic Lacquer It is a lacquer with chemical resistance. and has low permeability especially the sulfide ions, which is why it is commonly used in the coating of meat and fish cans.
- Acrylic lacquer is a lacquer suitable for coating cans that are subject to thermal processing because of its high heat resistance. Originally, this type of lacquer was only used to coat the outside of the can, but nowadays it is used to coat the inside to have a beautiful white color without adhering to black stains as well.
- Epoxy phenolic lacquer is the most commonly used lacquer today for both canning coatings made from steel and aluminum due to its acid-resistance properties highly flexible clings tightly and high heat resistance This type of lacquer can also be subdivided into many more which covers a wide range of applications Whether it is juice, fruit, vegetables, soups, meat, fish, etc.