Tin cans. Angela / Pixabay.com / 2009 / CC0 1.0
Cans (aka tins) are metal containers (usually cylindrical but not necessarily) in which food or drink is hermetically sealed for storage over long periods of time.
Construction of cans
Cans for food are typically made of “three different materials: aluminum, tin-coated steel (tinplate) and electrolytic chromium coated steel (ECCS).” [1]Geueke, Birgi. Can coatings. Food Packaging Forum. 15 December 2016. DOI: 10.5281/zenodo.200633. Accessed November 2020 at https://www.foodpackagingforum.org/food-packaging-health/can-coatings
Metal cans provide physical protection, barrier properties and recyclability, and can be heat-treated and sealed for sterility. . [2]A glossary of common packaging materials. University of Turin. In: Consumer and Environmental Safety: Food Packaging and Kitchenware. Module 1, Step 5. Accessed November 2020 at https://www.futurelearn.com/courses/consumers-and-environmental-safety-food-packaging-and-kitchenware
The metal of cans can corrode, however, so the cans need to be coated with a protective layer to both protect the food from the metal, and the metal from the food:
“Highly acidic foods and some food ingredients promote corrosion of metal leading to leakage of the can and spoilage of the food. In addition, coatings prevent reactions between the can’s metals and the food which could e.g. result in unwanted cloudiness of beverages or staining of food.” [3]Geueke, Birgi. Can coatings.
Several different types of coating can be used to protect the integrity of food cans from effects of the food they hold:
“Cans are typically coated internally and externally with thin films (1 to 10 µm) that protect the integrity of the can from effects of the food and prevent chemical reactions between the metal and the content. Epoxy-based coatings have the highest market share of more than 90%. However, food companies have started to replace BPA-based epoxy coatings with alternatives, following some toxicological evidence and recent regulations. Acrylic and polyester coatings are currently used as alternatives and, more recently, polyolefin and non-BPA epoxy coatings are being used. Further inventions include BPA capturing systems and top coatings. These alternatives are usually more expensive than epoxy coatings.” [4]A glossary of food contact materials and key terms. University of Turin. In: Consumer and Environmental Safety: Food Packaging and Kitchenware. Module 1, Step 6. Accessed November 2020 at https://www.futurelearn.com/courses/consumers-and-environmental-safety-food-packaging-and-kitchenware
Other coatings used for food cans include acrylic, oleoresins, phenolic, polyester, polyolefins and vinyl.
Can sizes
The size of a can cannot be taken as an indication of how much weight in food it will hold. Cans that are the same size can vary in weight after they are filled, depending on what they were filled with of course. And, every can, during filling, must leave some headspace, and not be filled right up to the very top.
In North America, metrification of can sizes hasn’t necessarily led to rationalization of can sizes.
When you see three digit numbers, they are created as follows:
- The first number of the three digits represents the number of whole inches. So, in a 303 can/ tin, the first three represents 3 inches (7 ½ cm);
- The final two numbers represent sixteenths of an inch. So, in 303, the “03” part at the end represents 3/16ths of an inch (4.7 mm.) So the total size of the can is 3 3/16 inches.
When the full dimensions are given, they will look like this: 303 x 407 (3 3/16 x 4 7/16.) The first number given is the width; the second is the height. So, the Can in our example is 3 3/16 inches (8.1 cm) wide x 4 7/16 inches (11.3 cm) tall. As a short form, usually just the first dimension of 303 is given — the width.
North American Can Sizes Chart
The standard sizes that evolved in North America were numbered 1 through 10 (plus a 2 ½ size.)
In North America, some older recipes used these can sizes as a measurement of how much of an ingredient they were calling for.
| Size Number | Dimensions | Volume of Food (approx.) | Weight (approx.) | Usage |
|---|---|---|---|---|
| ¼ | ½ cup | 4 oz | Individual portions. | |
| ⅜ | ¾ cup | 6 oz | For both individual portions of fruit juices, and frozen juice concentrates. | |
| ½ | 1 cup | 8 oz | Portions of vegetables and fruits for 2 people. | |
| #1 | 1 ⅓ cup | 11 oz | Fruit, vegetables, condensed soups. | |
| No. 1 picnic | 211 x 400 | 1 ¼ cups | 10 ½ to 12 oz | Mostly condensed soups, but also some fruits and vegetables. |
| #1 tall | 301 x 411 | 2 cups | 16 oz | Mostly condensed soups, but also some fruits and vegetables. |
| #1 square | 2 cups | 16 oz | ||
| No. 2 | 307 x 409 | 2 ½ cups | 20 oz | Juice, uncondensed soup, pineapple and apple slices, fruits, vegetables. Tomatoes. |
| No. 2 cylinder | 307 x 512 | 26 ½ oz of water | ||
| No. 2 vacuum | 307 x 306 | 1 ½ | 12 oz | Mainly used for vacuum-packed sweet corn kernels. |
| No. 2 ½ | 3 ½ cups | 27 to 29 oz | Fruit, tomatoes, sauerkraut, pumpkin puréed, spinach. | |
| #2-½ square | 4 cups | 31 oz | ||
| No. 211 | 211 x 414 | 1 ½ | 12 oz | Cylinder-shaped |
| No. 3 | 5 ¾ cups | 51 oz | Cylinder shaped. Juices. Institutional sizes of pork and beans, condensed soups and some vegetables. |
|
| #3 squat | 2 ¾ cups | Looks like a No. 3 can cut in half. Baked beans. | ||
| No. 3 cylinder | 404 x 700 | 5-¾ | 46 oz | |
| No. 300 used to be #4 | 300 x 407 or 300 x 509 (cylinder) | 1 ¾ cups | 14 to 16 oz | Baked beans, cranberry sauce, chili, canned macaroni. |
| No. 303 | 303 x 406 | 2 cups | 16 to 17 oz | Main size post 1980s for fruits, vegetables. |
| No. 303 cylinder | 303 x 509 | 22 oz | 22 oz | |
| #5 | 502 x 510 | 7 ⅓ cups | Large tins for tuna | |
| No. 10 | 602 x 700 or 603 x 830 | 3 quarts (12 cups) *may hold up to 1 cup more based on size of the can | 6 ½ pounds to 7 pounds and 5 oz | Institutional sized fruit, vegetable. |
Storage Hints
It’s generally still considered a big no-no to store food in an opened can. The American Food Products Association says: “Once opened, leftover contents must be removed from the can and placed in a covered, non-metallic container and refrigerated or frozen.” [5]2005. Retrieved from http://www.fpa-food.org/content/consumers/faqs.asp.)
History Notes
At first, every manufacturer made its own cans for its own food. In 1928, when Heinz first started canning baked beans in the UK, it made its own cans at its factory in Waxlow Road, Harlesden, north-west London (later to be bombed twice during World War Two.) Crosse & Blackwell made their own cans in Bermondsey in South London, a centre of can production.
At a certain point, the desire for standardization came about. This allowed food processors to buy cans from third-party suppliers and realize cost savings. Note that as of the early 2000s, at least, Heinz in the UK had gone back to making its own cans.
See also the Preserves History section.
Can Openers
Pullman Cans
References
| ↑1 | Geueke, Birgi. Can coatings. Food Packaging Forum. 15 December 2016. DOI: 10.5281/zenodo.200633. Accessed November 2020 at https://www.foodpackagingforum.org/food-packaging-health/can-coatings |
|---|---|
| ↑2 | A glossary of common packaging materials. University of Turin. In: Consumer and Environmental Safety: Food Packaging and Kitchenware. Module 1, Step 5. Accessed November 2020 at https://www.futurelearn.com/courses/consumers-and-environmental-safety-food-packaging-and-kitchenware |
| ↑3 | Geueke, Birgi. Can coatings. |
| ↑4 | A glossary of food contact materials and key terms. University of Turin. In: Consumer and Environmental Safety: Food Packaging and Kitchenware. Module 1, Step 6. Accessed November 2020 at https://www.futurelearn.com/courses/consumers-and-environmental-safety-food-packaging-and-kitchenware |
| ↑5 | 2005. Retrieved from http://www.fpa-food.org/content/consumers/faqs.asp.) |