The other day, I was on Instagram just browsing. Obviously, my interests include tin cans, packaging, and how people use them. I came across a picture of beautifully baked bread in old tin cans. This took me back to the time I was living in the US where a lot of people did this. I love people finding ways to reuse cans and I love the way they look but being in the business for so long and having just filled a food contact questionnaire for a new client very recently, I knew I had to say something.
Tin cans are made out of tin plate which is essentially steel covered with a thin layer of tin to prevent corrosion. When I say tin cans, I mean anything from your soup cans, olive oil cans to cookie tins, popcorn tins, and anything in between. Most beverage cans don’t fall into this category as they are made out of aluminum. And most tin cans that will be in contact with food are coated with a special food-grade lacquer depending on the food.
Lacquer application is very straight forward. A thin layer of lacquer is applied on a flat tin plate by a machine called a coater before the cans are formed. After the application, it is cured at about 205 °C (~ 400 °F) for about 12 minutes and it’s done. Different types of lacquers might differ in temperature and duration but I think you get the idea.
Now the tin plate goes into can making, the cans are formed, packed, and sent to the client for filling. We don’t make cans for preserved food such as soup and vegetables but if that is the case I know that they go into a process called sterilization. It is a special procedure of heating the filled cans to 121 °C (~ 250 °F) for a minimum of 15 minutes to destroy any microorganism and extend shelf life. From a manufacturer's perspective, this is the end of the heat cycle, and tin cans will be stored at room temperature or colder.
I have seen so many articles on the internet talking about how the cans come in contact with high temperatures during production or filling making it ok for baking. I gave you all the technical details so that you can make a comparison for yourselves. As an amateur baker myself, I know that bread is usually baked at temperatures over 200 °C (~ 390 °F) for longer than 20 minutes. Doing anything on the stove might mean even higher temperatures. This is much hotter and much longer than any process we have in our production.
Obviously, this comparison isn’t what we do when we talk about food contact. We conduct migration tests. A migration test measures the amount of substance that is transferred to food. To simulate different types of food and storage conditions, there are different procedures. There are very strict EU and FDA regulations that define the limits that lacquer manufacturers must adhere to.
So what did I say to the person who posted the photo on Instagram? I just DM’ed and said that it might be risky to bake directly in a can and explained why. I received a reply thanking me for the warning. Knowledge grows when shared. I am sure there will be a time when we will be able to bake in cans but until then maybe it is better if you place your goodies in them after you bake them.