The Myth: You can’t cook wine, tomatoes, or other acidic ingredients in a cast-iron pan.
THE TESTING: When acidic ingredients are cooked in cast iron for an extended amount of time, trace amounts of molecules from the metal can loosen and leach into the food. Although these minute amounts are not harmful to consume, they may impart unwanted metallic flavors, and the pan’s seasoning can be damaged as well. To test how fast this happens and how noticeable it is, we made a highly acidic tomato sauce and simmered it in a well-seasoned skillet, testing it every 15 minutes to check for off-flavors and damage to the pan.
THE TAKEAWAY: In the end, our tasters could detect metallic flavors in the tomato sauce only after it had simmered for a full 30 minutes. So, while you can definitely cook with acidic ingredients in your cast-iron skillet, you have to be careful. First, make sure your pan is well seasoned; seasoning keeps the acid from interacting with the iron—to a point. An acidic sauce can afford a brief stay in a well-seasoned pan with no dire consequences. You should also be careful to remove acidic dishes from the skillet after they finish cooking; don’t let them sit too long in the warm skillet and transfer any leftovers to an airtight container. (These rules do not apply to enameled cast-iron skillets; the enameled coating makes it safe to cook acidic ingredients for any length of time.)
All of our cast-iron recipes have been carefully developed to work in cast iron, even when they use highly acidic ingredients like vinegar, wine, tomatoes, cherries, and stone fruits. We use tricks like shorter simmering times, diluting the problematic ingredients to make the pH less of an issue, and waiting until late in the recipe to add the acidic ingredients. If you do accidentally oversimmer an acidic ingredient, you may have to throw out the food, but you can simply reseason your skillet and get back to cooking in it again.