There is a prevailing belief that using canned tomatoes in, for example, an Italian sauce, will render a horrible metallic taste. This taste is often referred to as “tinny.” The only way to mitigate this bitterness is to cook the sauce for several hours until the taste is “cooked off.” Is there a metallic taste in canned tomatoes, and can this taste be cooked away? Is it the metal from the can? No. While there can be a bitter taste associated with canned tomatoes, it is not metal that has leached from the can. The bitter taste, instead, comes from the tomatoes themselves. Still, it may taste metallic! Where does this taste come from, and what can you do about the metallic taste in canned tomatoes?
Canned Tomatoes Taste Metallic? Why it Happens & How to Fix It
- The Cause: It’s usually tannins in the tomato skins and seeds—not metal from the can—that create that “tinny” sensation.
- The Fix: You can cook off the bitterness by simmering the sauce for 1–2 hours to break those tannins down.
- Quick Save: While you can’t “neutralize” tannins instantly, you can mask the metallic edge with a pinch of sugar or a tiny amount of fat (like butter or cream). These coat the palate and make the bitterness less noticeable until the sauce has time to simmer.
- Safety Check: It is perfectly safe to eat. As long as the can isn’t bulging or damaged, the taste is a quality issue, not a toxicity risk.
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.
🍅Did you know? Canned tomatoes, despite protests from grumpy chefs, are often better for cooking! When tomatoes are out of season or you don’t have access to high-quality fresh tomatoes, go for a good (not dirt cheap) can of tomatoes.
Why Do Canned Tomatoes Taste Metallic?
The presence of a metallic taste in canned tomatoes has nothing to do with the food being canned. Many sources admit that the taste is the result of the tannins in the tomatoes, present in the skins and seeds. However, these same sources claim it is because of the tannins reacting with the metal of the can. This is not possible. 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 way to counteract a bitter taste is by adding a sweetener. In tomato sauce, some finely minced carrots can help, or some table sugar, but it is not the best solution.
Tin-Lined Cans Do Not Exist
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. This was intended to stop the can 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.
🌿The Allure of Vine-Ripened Tomatoes: Buying vine-ripened tomates, often sold with some “vine” still attached, surely must be better than regular old tomatoes. Tomatoes that ripen on the vine just taste better! Don’t be so sure!
Modern Cans Have Protective Plastic Coatings Inside
However, it is 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?
While many consumers are concerned about BPA being used in the lining of metal cans, most modern can manufacturers have moved away from BPA and are now using polyester or acrylic linings.
🍵 Related Food Science: The same bitter polyphenols that make canned tomatoes taste “tinny” are also responsible for ruining a batch of tea. But does brewing tea in the fridge actually help? Find out why fridge tea is a myth and how temperature controls bitterness.
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. If you were to place solid tin in your mouth, you probably wouldn’t taste anything.
Another 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.
Is the Pomato Real? Did scientists really manage to cross a potato with a tomato, creating the pomato? Find out why an actual pomato plant is neither a feat of genetic engineering nor a miraculous one! >> Read More.
Canned Tomatoes Are Often Better For Cooking
Ironically, when making a tomato sauce, high-quality canned tomatoes are often a better choice than fresh tomatoes, especially when tomatoes 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 ten times, I doubt you would detect a metallic taste more than twice out of those ten 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 that 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.
Adding Sugar to Counteract the Bitter Metallic Taste
As explained above, it is possible to break down bitter tannins by a long application of heat. You may also see advice about adding sugar to counteract bitterness. This could help, but sugar is more necessary to counteract high acidity. If your tomato sauce does taste bitter and metallic, then your grandmother’s advice holds: Cook it longer.
While baking soda is often suggested to neutralize acid, it won’t break down the bitter tannins. Only a long application of heat can truly ‘cook off’ the metallic sensation by changing the structure of those compounds.
Low Quality Canned Tomatoes May Be More Bitter
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.
Frequently Asked Questions
Is it safe to eat tomatoes that taste like tin? Yes, it is perfectly safe. While a metallic taste can be off-putting, it is almost always a quality issue caused by the natural tannins in the tomatoes reacting with your palate, rather than metal leaching from the can.
How do you get the metallic taste out of canned tomato sauce? The best way to remove the “tinny” flavor is to simmer the sauce for 1 to 2 hours. This heat breaks down the tannins responsible for the bitterness. For a faster fix, add a tiny pinch of baking soda to neutralize the acidity or a teaspoon of sugar to balance the flavor.
Why does my tomato sauce taste like metal? Most “metallic” flavors in modern canned tomatoes come from high concentrations of tannins in the skins and seeds of lower-quality fruit. Since modern cans have non-reactive plastic linings, the food rarely ever touches actual metal.
