Something I’ve often seen judges on Food TV competitions do is go ballistic because someone used canned tomatoes. And then, they go and bring up that “tinny taste.” You didn’t cook off the tinny taste! Yes, these TV chefs have such amazing palates they can taste the can. No matter if there is no tin in the can, they can taste the tin of history! Forget about the plastic lining that ensures the food doesn’t actually come into contact with metal. It’s not going to fool these magical palates! Now, you and I both know that if there was any “tin” in, canned tomatoes, you couldn’t “cook it off.”
This claimed is tied to other foods but it is especially applied to canned tomatoes and this is important since it informs my later conclusions. The belief is that using canned tomatoes in, for example, an Italian sauce, will render a horrible tinny taste unless you cook the sauce for a long time so that the taste goes away. Is there a bad metallic taste in canned tomatoes and can this taste be cooked away?
Tin-Lined Cans
In the past, acidic foods preserved in cans did react with the metal in the cans, producing a metallic taste. Tin has been used as a lining for other types of metal cans. This was not pure tin but an electroplated mixture of tin and other materials that produced a thin layer on the inside of the can to prevent the food from coming into contact with the steel of the can to stop it from rusting.
Is Tin Reactive With Acids?
Tin is sometimes said to react with acids but it only reacts to strong acids. Tin is not likely to react significantly with the relatively weak acids in tomatoes due to their low concentration. If the tomatoes were to react, the chemicals formed would depend on how tin reacts with the specific acids in tomatoes, such as malic acid, citric acid, etc. While some reactions might produce tin that leaches into the food, others may not.
Modern Cans Have Protective Plastic Coatings Inside
However, it is highly unlikely to virtually impossible to find canned tomatoes with a tin lining. Today, tomato cans use a protective plastic lining that is completely nonreactive and much more protective than tin. Tin is very infrequently used for linings, except in some fruit juices and low-acid fruits. Therefore, there is no tinny taste in tomatoes that comes from the cans. And since tin does not appear to have a taste that humans can detect, you would probably never be able to taste it in food in the first place.
So, there is no such thing as “tinny” taste, at least as it relates to tin. What most people mean by tinny is “metallic.” This leads us to the next question: Do metals have a taste?
Can We Taste Metals?
The only way that we could taste a solid metal is if our saliva can corrode the metal in such a way as to produce ions that our taste buds can then detect. Therefore, we can detect a “metallic” taste associated with some metals, but not all. Metals like gold have very little taste, if any. Zinc and copper have very strong metallic and bitter tastes. You can test this by putting a copper penny in your mouth.
The only other way we can detect a metallic taste is if metal ions are present in liquid solutions, as may happen when metal leaches into a food from a cooking pot. Aluminum is highly reactive to acidic foods, causing aluminum to leach into the food and this can be detected as a taste. So, it is quite possible for us to taste something metallic in our food.
However, this taste will remain no longer how long we cook the food. In fact, the longer cooking time would just cause more metal to leach into the food, in the case of an aluminum pot. This would also produce off colors. Once this happens, there is no way to fix it.
In the days before cans were lined with protective layers, it was probably common for foods stored in cans to have a metallic taste. Few people alive today, if any, will remember this! Once tin was used, this would have solved most of the problem, as tin is nonreactive, at least in the low-acid environments on the inside of cans. While over time, it is possible for tin to react with acidic foods, we would probably not taste any tin that occurred, but instead taste any other metals that became present in the food due to the protective tin coating having been compromised. So, “tinny” as a descriptor was always inaccurate.
That “Tinny” Taste is Probably Not From Metals
Today, however, the presence of a metallic taste has nothing to do with the food being canned. This “tinny” taste often associated with metals, is sometimes said to be a result of the tannins in the tomatoes, present in the skins, and seeds. etc. However, these same sources claim it is because of the tannins reacting with the metal of the can. As we’ve already covered, this is not possible as the tomatoes in a modern can cannot come into contact with the metal can itself.
So, what’s the problem here? What people perceive as a metallic taste most often occurs in low-quality canned tomato products. Tannins taste bitter and cause an astringent sensation. It may be the bitterness of the tannins combined with other elements in a dish that produces a taste perceived as metallic.
However, this same metallic taste can be found in over-steeped tea and sometimes coffee. Not everyone will describe this bitter tannic taste as metallic but, regardless, the best fix to counteract a bitter taste is by adding a sweetener. In tomato sauce, some finely minced carrots can help, or some table sugar.
Ironically, when making a tomato sauce, high quality canned tomatoes are often a better choice than fresh tomatoes, especially when they are out of season or you generally do not have access to good-quality fresh tomatoes.
I do think that when TV food competition judges have complained of a tinny taste as often happens on Top Chef, they have, at times detected a bitterness that they have learned to call “tinny” because they have been taught it comes from the can. They then ask the competitor if they used canned tomatoes or some other product, and often the answer is yes. At other times, they already know that the competitor used a can.
If you used canned tomatoes 10 times I doubt you would detect a metallic taste more than twice out of those 10 tries, and I’m being generous. So, these TV chefs, who seem to always get a tinny taste out of the can, are almost certainly being pretentious much of the time and pretending that any canned product is inferior, even when it is a high-quality canned product.
If there are actual metal ions in your food, whatever caused it, longer cooking times would not fix it. The reason I think all this is important is just about every source you will find on this question is repeating things they have heard from TV chefs, who are often seen as infallible and all-knowing.
Yes, You Can Cook Off That Tinny Taste
Having said all that, if this taste is caused by tannins, then longer cooking times should significantly reduce them as they will be broken down by the heat. If cooked long enough, then most of the tannin content could be removed. I suspect many cooks discovered, by experience, that as they continue to cook their sauce, the tinny taste disappears over time as the tannins break down. Their technique is not wrong, only their explanation. They blamed the can instead of the can’s contents.
You may see advice about adding sugar to counteract bitterness. This could help but it’s more necessary to counteract high acidity since, again, a longer cook should help deal with bitter tannins. Yes, I know that was a long and winding way to tell you that if your tomato sauce is bitter and tastes “metallic” you should cook it longer. The purpose of this article was to debunk the notion that a tinny taste in canned tomatoes is caused by the can! It is not. Since it is not, then not all canned tomatoes will have a bitter metallic taste. It is solely the quality of the tomato product itself, not the can, that determines this.
Note that having a metallic taste in your mouth can be caused by a number of medical conditions, medications, vitamin deficiencies, and poor oral hygiene.
