Which pans should I not cook acidic food in?
Tomatoes, wine, vinegar and lemon react with some pan materials, stripping surfaces and putting a metallic taste into the food — which pans are reactive and what to use instead.
- Difficulty
- beginner
- Time
- 6 min
- Read
- 3 min
Short answer
Reactive: bare cast iron and carbon steel (strips the seasoning), bare aluminium and unlined copper (metallic taste, pitted metal). Non-reactive and fine for anything acidic: stainless steel, enamelled cast iron, glass, ceramic and non-stick. A quick splash of wine to deglaze is fine in an iron pan; an hour-long tomato simmer is not.
This is one of the few genuine material restrictions in a kitchen and it explains several confusing experiences — a tomato sauce that tastes faintly of coins, a beautifully seasoned pan that has gone patchy and grey, an aluminium pan that has developed dull pitted marks.
Step by step
- Know which materials react.Bare cast iron and carbon steel: acid dissolves the polymerised seasoning and then attacks the iron beneath, giving a metallic taste and a stripped patch. Bare aluminium: acid pits the surface and leaches into the food, most noticeably with tomato. Unlined copper: reacts readily and is why cooking copper is lined with tin or steel — the exception is a copper bowl for egg whites, where the reaction is the point.
- Know which materials do not.Stainless steel, enamelled cast iron, glass, glazed ceramic and stoneware, and non-stick coatings are all effectively inert. Any long-simmered tomato, wine, vinegar or citrus dish belongs in one of these.
- Judge by contact time, not by presence.This is a matter of degree. Deglazing a hot iron pan with a splash of wine for thirty seconds does essentially nothing. Simmering a ragù in it for two hours strips the seasoning and tastes of iron. The same logic applies to squeezing lemon over a fish just cooked in carbon steel — brief contact, no problem.
- Watch for the signs.A metallic or coin-like taste in a tomato or wine dish. Grey or dull patches on a previously dark seasoned pan. Dark discolouration in the sauce itself, particularly with tomato and with anything containing egg. Pitting or dulling on the inside of an aluminium pan.
- Re-season after any acidic accident.If you have stripped a patch on a seasoned pan, scrub it clean, dry it on the heat and put two thin coats of oil on. The pan is not damaged, it has just lost its surface in that spot.
- Use the right pan from the start.Keep a stainless or enamelled pan for tomato sauces, wine reductions, vinegar-based braises, chutneys and anything citrus-heavy. Preserving and pickling in particular should never go near bare iron, aluminium or unlined copper — long boiling with a lot of acid is the worst case for all three.
Tips
- Aluminium foil is the same problem in a different form: wrapping strongly acidic food in foil for a long time pits the foil and leaves grey marks on the food. Use baking paper between the food and the foil.
- A well-established, mature seasoning on cast iron resists a short acidic cook far better than a young one. Give a new pan a few months of fatty cooking before you try a tomato sauce in it.
- Enamelled cast iron gives you cast iron's heat retention with total acid resistance, which is exactly why it is the classic pot for a long braise with wine or tomato.
- Stainless steel discolouring during an acidic cook is a different thing — that is usually a heat tint or a mineral deposit, and it is cosmetic.
Questions people ask
Can I cook tomato sauce in cast iron?
A quick one, in a well-seasoned pan, yes. A long simmer will strip the seasoning and can leave a metallic taste. Enamelled cast iron has no such limit and is the better choice for anything over about twenty minutes.
Is it dangerous, or just a taste problem?
For iron and aluminium in normal domestic amounts it is a taste and a pan-damage problem rather than a health one. Unlined copper is the exception — copper can be genuinely toxic in quantity, which is why cooking copper is always lined.
What about stainless steel — is that reactive?
No. Stainless is the standard non-reactive kitchen material and handles anything acidic indefinitely. Its chromium oxide layer is what makes it stainless and it is not disturbed by cooking acids.