There are many ways to pack and preserve food. That includes canning, pickling, drying, freeze-drying and more. Some of these involve storing the food in containers such as jars and cans.
But canning has been the primary food preservation method, and it’s the most used method nowadays due to its efficiency and recyclability. The combined properties of tin and aluminium that are resistant to corrosion and 100% recyclable make for packaging food safely and ensure the food lasts longer. The most common food packaging that’s widely used nowadays is tin cans.
Tin cans for food packaging come in different forms. There are the most common cylindrical cans, square cans, and rectangular cans. Manufacturers use all kinds of tin cans for food packaging. But aside from shape, size and form, tin cans are categorised into two main types: two-piece tin cans and three-piece tin cans.
We’ll go over the details of these types and how tin cans are used in the food packaging industry.
TYPES OF TIN CANS FOR FOOD PACKAGING
There are only two main types of tin cans for food packaging: Two-piece tin cans and three-piece tin cans. Let’s have a look at how these two are different.
- Two-piece tin cans – Two-piece tin cans are called two-piece cans since they only have two pieces that make up the entire can: the cylinder for the body and bottom part and the lid. Most two-piece cans are made through a process called metal drawing, and one piece of the metal is compressed and shaped into a cylinder and added a lid on top. Metal drawing is a metalwork process that involves stretching the metal in a machine to produce the desired shape. Aluminium and tinplate cans are usually stretched thin depending on the type of food that is stored in the can. Thin cans are for beverages, while thicker cans are for storing foods such as sardines, tuna, meat and such.There are different types of two-piece cans depending on the drawing process.
- Single-drawn cans are made in one drawing operation instead of other metal-drawn cans. These are usually used for tuna, sardine and ready-meal cans.
- Drawn & Redrawn cans are cans that are tall and large and usually made for storing large portions of food such as salmon and canned fruit. These cans require more than one drawing operation known as draw and redraw. Depending on the can size, it can take multiple redraws to achieve the desired shape. Some of these cans are shaped with the top part larger than the bottom to allow stacking of various cans for easy transport.
- Since these are tall cans, drawn and Wall-Ironed or DWI cans are commonly used for beverages and beers. These cans are made by a process called wall ironing which pushes the cylindrical can into a machine that presses its walls on all sides simultaneously, and a punch is pushed down in the middle to flatten the thickness of the wall and increase the can’s length.There are more steps to do in the process for a beverage steel can than aluminium cans. These cans are cleaned 4-6 times in multiple stages with a washer using different treatment chemicals depending on the type of metals. The washing process comprises stages where the cans are cleaned and stripped off the lubricants used in the drawing and wall-ironing process. The cans are rinsed with deionized water for the last stage to create a contaminant-free surface. Once everything is done, the exterior is then decorated and cured inside an oven.
- Drawn and Ironed or DI cans are a different variation of DWI cans; only these are for packaging food products and pet food. These cans are not decorated like DWI cans.
- Three-piece tin cans – These cans are the traditional cans that are composed of a body, lid and bottom. As opposed to two-piece cans where the cylinder part is already made with a bottom part, three-piece cans separate the bottom and lid from the body to allow opening on both ends of the can. These are usually common tin cans for food packaging but can also be used for non-carbonated beverages.
WHAT ARE SOME OTHER MATERIALS USED IN FOOD PACKAGING CANS?
There are many materials that are used to make cans, and here are the most common ones:
Tin-plated steel or metal
Traditionally, cans made of steel aren’t recommended for food packaging since the metal can corrode due to the preservation of chemicals and materials in the food, which could lead to food contamination. Because of this, steel or metal cans are coated with a tin plating when used for food packaging.
Tin is a soft malleable non-toxic metal. Its non-corrosive property is why it is used as a coating in steel cans to prevent contamination into the food when steel corrodes.
In a tinplated can, there’s only about 1 – 2% tin and the rest are iron or steel materials. Since tin is only a protective layer to protect the food, and the rest of the material is iron and steel, most tinplated cans are heavier than modern tin cans and are more expensive and harder to transport.
Nowadays, the most common component of cans for food packaging is tin. Due to its resistance to corrosion and malleable property, it’s used in most cans for food preservation. Since tin is a rare mineral, most modern cans are made of aluminon and other soft non-corrosive metals.
Tin is also recyclable and can be reused multiple times, which makes it the recommended material for can packaging.
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