They are lined with an epoxy resin to protect them from corrosion or to keep harmful bacteria from getting into a damaged can. But, some say when the lining is made with a chemical known as BPA. BPA was originally developed as an estrogen therapy.
Plastic linings. Many metal food cans are lined with plastic, to prevent the food from corroding the can.
A common misconception is that it's white to prevent a chemical reaction between the metal and the product inside, but nearly every tin we buy these days will have a coating – it'll just be clear rather than white. This film is made of a plastic called epoxy resin, a heated and shaped plastic.
Non-BPA Linings in Cans Protect Your Health
The metal can, lined with can coatings, is one of the safest processes for preserving food and preventing the growth of microorganisms that cause foodborne illnesses.
For now, BPA is used in about 10 per cent of tinned foods. In the US, it's much more widely used. A 2016 report found two out of three cans tested in America contained BPA.
How can I reduce my exposure to BPA in canned and bottled food and drinks? Choose food and drinks that do not have Proposition 65 warnings for BPA, if possible. For canned food products such as fruit and vegetables with Proposition 65 warnings for BPA, drain and rinse the contents before eating, if possible.
1940's and 1950's: New use of BPA in plastic.
The chemical industry begins to use BPA to manufacture a hard plastic called polycarbonate, and to make epoxy resins used as linings for metal food cans and a variety of other products.
The inside of the can is lined by spray coating an epoxy lacquer or polymer to protect the aluminum from being corroded by acidic contents such as carbonated beverages and imparting a metallic taste to the beverage.
Exposure to BPA is a concern because of the possible health effects on the brain and prostate gland of fetuses, infants and children. It can also affect children's behavior. Additional research suggests a possible link between BPA and increased blood pressure, type 2 diabetes and cardiovascular disease.
Cans are typically made of aluminum or tin-plated steel. While these materials are considered safe for packaging beverages, there is a potential risk of exposure to metals when you drink directly from the can. Prolonged exposure to certain metals may lead to health issues.
Canned food has been around for a long time and since the 1960's, a thin epoxy lining made with the chemical BPA has been used to protect the inside of the can from corroding. Corroding metal is not good, so a liner is definitely needed in order for canned food to have a good shelf life.
In the tinplate process, the tin, which can be made extremely thin, forms a coating over the steel; tin makes up just one to two percent of tinplate. Because of modern processes that give steel improved corrosion protection, tin is no longer needed.
Canned food should not be cooked in the can, as doing so can release harmful chemicals from the can and plastic lining into the food. Cans made of tin, aluminum, steel, and other metals can release toxins such as chromium and nickel when heated.
The term “#10 can” refers to its volume rather than its physical dimensions. A #10 can hold up to 2.8 liters of food (weight can vary product pending).
Many food manufacturers and grocery retailers — including major companies such as Campbell's, Del Monte, General Mills, Target, Safeway and Walmart — continue to sell their food products in cans lined with the chemical bisphenol A (BPA), despite promises from some of the companies that they would stop the practice, ...
Material Composition
Tin cans are predominantly made of steel with a tin coating. Aluminum cans are primarily made of aluminum, which is naturally corrosion-resistant.
In addition to plastic containers and water bottles, BPA is found in unlikely places, such as printed receipts and dental fillings. BPA can be eliminated by supporting liver detoxification and cultivating a healthy microbiome with organic foods, antioxidants, and specific supplements.
In vitro and animal toxicological studies have consistently reported a potential for decreased female fertility resulting from BPA exposure due to disruption in oocyte maturation, decreased ovarian E2 synthesis, and early pregnancy loss [48-51].
Since Tupperware is such a popular brand of plastic food storage containers, it is not surprising how many people have questioned whether Tupperware material contains BPA. Tupperware officially states that since 2010, they have not sold items containing BPA.
Yep, it's true. Aluminum cans have a thin plastic liner that buffers the liquid from the metal.
Inner coating
The inner coating is mainly used to protect the inner surface of the tin can to prevent the substance in the can from direct contact with the metal, thereby avoiding chemical reactions and corrosion. Common inner coating materials include epoxy resin, polyester, polyurethane and acrylic resin.
The liners are made by applying a thin layer of epoxy resin to the interior surface of the can, creating a barrier between the contents and the aluminum. Epoxy liners have been used for many years in the beverage packaging industry due to their excellent barrier properties, durability, and resistance to corrosion.
History of the Aluminum Can
Steel cans were used until 1958 when the first aluminum can was produced. Between 1958-1967 a hybrid can was developed featuring a steel can with an aluminum top, or some variant of the sort. By 1967 Coke and Pepsi were using all aluminum cans for soft drink production.
Some people suggested that tin was a British word originating from the material the container is made from, while can is a US word for a sealed metal container with all the air removed. More suggested that tin should be used for food and can for drink, while some said that the correct expression was 'tin can'.
In the US, Thomas Kensett and Ezra Daggett patented the use of tinplate in 1825 to sell canned oysters, fruits, meats and vegetables.