Today, let's dish about cookware. Occasionally you're going to see the words "non-reactive" ____________ (insert skillet, bowl, pan, etc. here) in a recipe. What does that mean? Time to take a field trip back to science class - it comes down to chemical reactions. Don't worry, I'm going to gloss over the technical stuff - but it boils down to mainly acidic foods reacting with certain metals, which will in turn change the taste of your food, and not in the way you want it to. Non-reactive cookware will not cause that chemical reaction. That doesn't mean you need to root through your cabinets and toss anything considered reactive. It just means we need to use a little knowledge on when to use them, and when to pull out the non-reactive stuff.
What's Non-reactive? What's Not?
Non-reactive cookware is a pretty broad category that includes non-metallic and metallic materials in it. Some prime examples of prep and cooking tools that are non-reactive are made of clay, stoneware, silicone, plastics, enamel, glass, and stainless steel. But stainless steel isn't the best metal for even heating, so sometimes these pieces may have an aluminum or copper bottom bonded to them. As long as the surface the food touches is stainless steel, it's non-reactive.
Reactive cookware is primarily made up of copper and aluminum, and includes cast iron. They are really good at heating up and retaining heat, but they react with acidic foods. This can give food a metallic taste or discolor it. That also means you shouldn't be storing your food in containers with these materials. (If you are stashing your leftovers in your cast iron pans, you need to be fussed at - you're killing your seasoning and promoting rust!) Copper pots may have a tin coating or lining to keep the cooking surface non-reactive, but as soon as the tin is scratched, your pot now has reactive spots. Cast iron is reactive, but if you've got a good seasoning on it, you should have no trouble cooking tomato-based and other acidic foods in it, as long as you don't let the food linger around.
When Should I Use What?
Non-reactive - Use it for marinades, vinaigrettes, acidic foods like tomatoes, light colored soups or sauces to avoid discoloration (that means no aluminum whisks for stirring, too).
Reactive - Good for general cooking. Don't forget about our note on cast iron - tomatoes are okay if you've got a thick seasoning on the pan, and you don't let the food sit around in the pan for a long time. Just don't get any funny ideas to use it to marinate stuff in it.