Technically, you can cook just about anything in a cast-iron skillet. It’s one of our favorite kitchen tools, and we use it for everything from Sunday morning pancakes and Dutch babies to seared steak and sautéed vegetables. Maintaining a well-seasoned cast-iron pan takes time and patience, but the coating only gets better and more protective with age and use. But there are three things you should avoid cooking in a cast-iron skillet if you’re not sure the pan has been properly seasoned and cared for. Ahead, we spoke to an iron cookware expert and food scientist to get their insights.
Using a Cast-Iron Pan
We’ll say it again: While there are very few things that aren’t perfectly paired with cast-iron cooking, there are hundreds that are. That’s why we use cast-iron pans for cooking almost every day.
Cast-Iron Is Nonstick
Cast-iron pans have a layer of seasoning that is essentially a protective coat between the raw iron and the exterior environment, explains Will Copenhaver, vice president, marketing and sales at Smithey Ironware Company, a cast-iron cookware company. “Seasoning occurs when a thin layer of fat like a cooking oil is heated and bonds to the metal itself in a process called polymerization,” he says. That protective nonstick barrier means cast-iron pans conduct heat very well, which is why so many people love to use them to sear foods like steaks, pork chops, and chicken breasts. The pan ensures even and adequate browning and it’s virtually impossible for the food to stick.
What to Avoid Cooking in Cast Iron
While a cast-iron skillet is our go-to pick for many foods, there are a few things you might want to avoid cooking in cast-iron. Whether you never cook these things in your cast-iron skillet or do it on the regular depends on both your technique level and how well-seasoned and cared-for your cast-iron skillet is.
1. Highly Acidic Foods (Like Tomatoes)
Over time, cooking with oils and fats continues to build a pan’s seasoning; cooking with acidic foods can erode that seasoning. Most people cook with both fats and acids, and any of the pan’s seasoning that’s lost to acidic ingredients is rebuilt by the cooking fats. Copenhaver notes that a well-seasoned cast-iron pan is extremely durable and can handle reasonable amounts of acidic cooking without noticeable change, but prolonged exposure can do some damage to a seasoning layer.
The most common acidic food you might not want to cook in your cast-iron skillet is tomatoes. Copenhaver encourages us not to be afraid of warming up tomato sauce for pasta, but if you plan to slow simmer this acidic ingredient for several hours, say for a tomato-based dish like Bolognese or Sunday sauce, you may want to consider an alternative vessel.
From a scientific perspective, Bryan Quoc Le, Ph.D., food scientist and author of 150 Food Science Questions Answered says that once that acidic erosion occurs on the surface of the pan, what’s left is the bare iron. This surface iron starts to react with oxygen found in the surroundings, forming thin layers of iron oxide and wearing down the quality of the pan. “The compounds responsible for making acidic foods acidic, such as ascorbic acid or citric acid, are very good at speeding up this reaction and binding to iron oxide, dissolving it away from the cast-iron surface,” he says.
In other words, the longer the surface is in proximity to the acidic sauce, the faster the cycle of oxidation and dissolving accelerates.
2. Delicate Fish
Cooking fish in a cast-iron skillet is less an issue of sticking and has more to do with how skilled a cook you are. Restaurant chefs can flip and sear the most flaky fish fillets with ease, but home cooks will have more success with another pan, like a standard stainless steel or nonstick skillet, especially when it comes to thinner and fragile seafood like sole or flounder.
3. Eggs
In order to cook delicate dishes like scrambled eggs or omelets without the eggs sticking, there are three things to consider:
- You need a very well-seasoned pan that has developed a reliably nonstick surface: The last thing you want to do is clean off stuck egg film from your pan. It requires harsh scrubbing, which isn’t good if you want to take care of your cast-iron skillet.
- Preheating your cast-iron skillet is essential: While you never want to add eggs to a smoking hot pan, allow time for the pan to preheat before lowering it to a more suitable cooking temperature for the eggs.
- Cooking temperature: The pan shouldn’t be too hot or too cold. Making eggs in a cast-iron skillet is a bit like Goldilocks finding the right temperature porridge—the heat needs to be just right. Eggs are delicate and overcook easily, becoming rubbery and tough. This can happen fast if the heat is too high. On the other hand, if the pan is too cold, the protein in the eggs can merge with the pan’s surface and stick.
