Acidic foods, like tomatoes, will have a chemical reaction based on the type of cookware you use.
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If you love to cook, then you likely already have an array of cookware in your cabinets, from cast-iron skillets to stainless-steel saucepans. These types of pans serve different purposes, though, based on how the food you cook will react to them. This is because they fall in two separate categories: reactive and non-reactive. Before you reach for a pan to cook your next meal, it's important to understand the difference between reactive and nonreactive pans, which will ensure you always reach for the correct pan for the task at hand.

various cooking pan styles on hanging rack
Credit: Robert Ruidl / Getty Images

Reactive Pans

"A reactive pan is one where highly acidic foods, such as tomatoes, citrus, and wine, react with the metal while cooking or storing these items," chef Jim Warner, the program director of food and nutrition in the nutrition services department at The Ohio State University's Wexner Medical Center, says. "This can draw a metallic taste when cooking or storing foods in a reactive pan or bowl." Commonly used reactive cookware includes cast iron, however, it is also the least reactive type explains Warner, as most cast-iron pans are seasoned with cooking oil which reduces the chance of it reacting with highly acidic foods. Aluminum cookware is another popular option that is reactive. "An example of aluminum reacting with acidic foods is when you cover a tomato-based food with aluminum foil such as lasagna," Warner explains. "When you remove the aluminum foil, you may see small holes in the aluminum with dark spots on the food where the aluminum has made contact with the food; the underside of the foil will also be discolored."

If you have aluminum pans that are coated with Teflon or other nonstick cooking surfaces, then they would actually be considered nonreactive (which we'll get to next). "Unlined cooper cookware can react with acidic foods but is safe to use when lined with another metal such as tin," Warner explains. "Using unlined copper pans will leave your foods with a bitter metallic taste." This is the result of the metal leaching into your meals from the chemical reaction of the food, metal, and heat when cooking.

Non-Reactive Pans

In contrast, non-reactive pans will prevent chemical reactions when cooking with foods high in acidity. Two of the most popular types? Stainless-steel and tin. "Manufacturers of stainless cookware may line the bottom of the cooking vessel with copper or aluminum due to stainless steel being relatively a poor heat conductor, with aluminum or copper enhancing the conductivity of the pan [in turn, making this reactive cookware]," Warner says. "Tin-lined pans are also a good choice, as tin does not react with food. Again, manufacturers may line cooking vessels with tin." There are other options on the market, too, like nonstick and Teflon. Keep in mind that some other types of cookware are great, but require particular care when you are cooking with them. "Cookware made ceramic, glass, or coated with enamel are also a good choice but you must avoid chipping or scratching the cooking surface or some of the material may end up in your food," he adds. Using a wooden, rounded spoon on your pans will help, as it won't scratch the surface and the shape will allow you to get in the corners of your pans. Softer wood in particular is what Warner suggests using when caramelizing foods and reducing sauces.

In order to keep up the quality of your cookware, Warner says avoid using an abrasive brush or cleaner on Teflon-coated pans. Simply use dish soap or baking soda with water for a cleaning solution, as strong chemicals that could wear at the quality. If your Teflon pan's surface starts to chip or peel, you'll know it's time to throw it out. For aluminum or stainless-steel pans, Warner says his go-to is Bar Keepers Friend ($4.95,  which he uses with a soft cloth and water. He adds that you should let glass or stainless-steel cookware cool down completely before washing. "Temperature shock may damage the pans over time and the glass may shatter."

Comments (4)

Martha Stewart Member
June 3, 2020
Actually cast iron is relatively a poor heat conductor, but is known for its heat retention. And while stainless steel cookware is true a poor heat conductor, almost all stainless steel cookware has either aluminium or copper core allowing it to be a better heat conductor than cast iron any day. Just wanted to clarify this for the readers.
Martha Stewart Member
January 5, 2019
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Martha Stewart Member
August 10, 2018
Unlined copper should not be used for cooking. Copper by itself is a poison. Small amounts of copper to leach into the food you are cooking. That's why copper pots and pans are traditionally lined with tin, or nowadays with stainless steel. Unlined copper bowls can be used for beating egg whites. Other than that, it's best to leave it alone.
Martha Stewart Member
September 17, 2017
While I used think there were some metals that are reactive and some other that are not, I was wrong and came to realize this after doing the 'Baking soda test for cookware toxicity' with all my metal cookware (aluminium, stainless steel, titanium, copper etc.,). All metals are reactive and leach into food. These metal ions are harmful in the body and cause various illnesses. In all my testing the safest cookware I found was MEC's pure-clay pots. These are not made from metals or ceramics (ceramic is reactive too and has toxic ingredients). They're made from primary clay. I've been using these pots ever since and am so happy I discovered them.