This question plagued me for a long time when I was learning to preserve. There are a lot of recipes that call for the use of a non-reactive pot, bowl or other mysterious vessel. I didn’t know what to think and, in most cases, I just hoped that the one I used was non-reactive because this language just seemed so foreign.
Then, one day, I made a little sauce out of berries and it tasted like metal. I suddenly figured I had an inkling of what a reactive pan was. Indeed:
A reactive pan is one that reacts chemically with foods – typically high acid foods (including most fruit and tomatoes – there’s a primer on the difference between high and low acid foods here)
Reactive pots can result in:
- discoloration of your final recipe
- a metallic taste in your food
The most common reactive pots (the ones to potentially avoid) are:
- aluminum (especially the lightweight stuff that is common in entry-level cookware – especially in the pots I used for many years in my kitchen)
- Unlined copper pans or pots.
Reactive pots tent to be good conductors of heat. Non-reactive pots include:
- Un-scratched enamel (Le Creuset)
- Stainless Steel
The above are non-reactive but tend to weaker conductors of heat when compared to the reactive ones.
There are also a set of exceptions to the common rule which are:
- Cast iron is reactive (and heats well). There are many people who cook high-acid foods in a well-seasoned cast iron pan without recourse. The secret tends to be how well seasoned the pan is and how long the acidic food sits in the pan (I wouldn’t make tomato soup in my cast iron frying pan but I’d toss tomatoes into my stir fry with it).
- Copper preserving pans are traditional in preserving – the combination of high-acid and sugar can yield non-metallic tasting results though it takes care and experience (that I am woefully shy of). For such experience, turn to Shae at Hitchhiking to Heaven who wrote a master-level tome on the subject and is just awesome. She is a proponent of copper – and I’m very curious to try!
Marisa at Food in Jars also wrote a piece of types of pans in 2010 that’s a great reference on non-reactive pans.