Metal food and beverage cans have a thin coating on the interior surface, which is essential to prevent corrosion of the can and contamination of food and beverages with dissolved metals (UK FSA, 2002).
Aluminium drinks cans have a polymer plastic lining. It’s there to stop acids in the beverage from corroding the metal which is not good for the can or the flavor of the contents.,If you don’t believe me, you can try this experiment, as done by Steve Spangler, to separate the two. However you will need to be “a chemistry teacher or someone with the proper training to handle hazardous chemicals”)
If you are neither, just make do with this picture.
You might wish to know that when the can is recycled, the liner is burnt off.
“The History of the Liner – Technicians at the American Can Company, even before Prohibition, began toying with the idea of putting beer in a can. As early as 1929, Anheuser-Busch and Pabst experimented with the canning process. Schlitzeven proposed a can design that looked like a small barrel.
The major problem the early researchers were confronted with, however, was not strength, but the can’s liner. Several years and most of the early research funds were spent to solve this perplexing problem. Beer has a strong affinity for metal, causing precipitated salts and a foul taste. The brewers called the condition “metal turbidity”.
The American Can Company produced the flat or punch top can in 1934. The lining was made from a Union Carbide product called “Vinylite”, a plastic product which was trademarked “keglined” on September 25, 1934.” Steve Spangler
Nearly all tin cans are plastic lined with epoxy resin.
They have been since the 50s.
In tins the liner can be white or yellow or transparent in which case it is undetectable. In most cases it is best to assume that your can has a plastic liner.
It helps to prevent canned foods from becoming tainted or spoiled by bacterial contamination.
Epoxy resins, are used because of their “exceptional combination of toughness, adhesion, formability and chemical resistance.”
these coatings make it possible for food products to maintain their quality and taste, while extending shelf life.
Bad for you?
You might not want to know that the lining contains Bisphenol A (BPA) a chemical building block that is used to make polycarbonate plastic and epoxy resins.
So what?? To cut a long story short it would seem that BPA is toxic and does leach from plastic liners into the food.
The Bisphenol A Organisation argues that it is in such small amounts as to be negligible.
Based on the results of the SPI study, the estimated dietary intake of BPA from can coatings is less than 0.00011 milligrams per kilogram body weight per day. Stated another way, an average adult consumer would have to ingest more than 230 kilograms (or about 500 pounds) of canned food and beverages every day for an entire lifetime to exceed the safe level of BPA set by the U.S. Environmental Protection Agency.
It is true that several scientific panels including the European Union’s Scientific Committee on Food, the National Toxicology Program and the Harvard Center for Risk Analysis have concluded that the claims that low doses of BPA affect human health have not (yet ), been substantiated. While accepting that animal testing has produced adverse results, they can find no concrete evidence that humans will react the same way.
BUT BPA is now considered by many to be a hormone disruptor, a chemical that alters the body’s normal hormonal activity. There are many counter claims on the internet and in the media that BPA is lethal. You can read all the arguments here
Why use BPA at all you might ask ? Here’s some information from the bishenol-a.org
It must also be noted that despite claims that BPA is as safe as safe, research is ongoing into alternatives. And maybe they have found one. According to Food Production Daily
“Researchers in the United States have developed a chemical derived from sugar with the potential to replace bisphenol A (BPA) in a number of products, including the lining of food cans. The New Jersey Institute of Technology (NJIT) said Professor Michael Jaffe had received a US patent for an epoxy resin based on isosorbide diglycidyl ether that could make consumer products safer.
“The patent will enable us to create a family of isosorbide-based epoxy resins that have the potential to replace bisphenol A in a number of products including food can linings”, Jaffe told FoodProductionDaily.com.
Note the statement by Food Production Daily that this will make consumer products safer. And I hardly need say that the creators of this new product are clear in their statements that BPA is not a good thing.
Hmmm – the choice is yours. As for me I boycott nearly all tins and cans – tonic, tomatoes, coconut milk, tomato puree and baked beans are the exceptions. I don’t like the plastic or the BPA.
You can find more reports, studies and media scares on BPA here
And how to make epoxy resin here