Won't "kill" either....may make the dish a little "iron" tasting.....but it's all good for you!

I cook tomato-ey things in my cast iron. As long as we don't let food sit in it, I don't notice an iron taste. I learned the hard way not to put a cast iron potful of spaghetti sauce in the fridge for two days.

The thing to watch out for is not to have other metalic object in the food in the cast iron cookware for a long time.

Electrolytic Corrosion (Electrolysis) occurs when
dissimilar metals are in contact in the presence of an
electrolyte, such as water (moisture) containing very
small amounts of acid.

Even stainless steel is not completely safe.

dcarch

Soo....after you cook your kale....and add the tomatoes, don't put a copper spoon in there and leave it for 3 months.

You will get some iron that dissolves into the tomatoes....but even if you cooked it for 5 hours, it wouldn't be enough to hurt you, but you may or may not notice an off flavor to the food, about the same way that I notice an iron taste to the water in some areas of the country.

When you have copper and iron together, given enough time, iron will be corroded. That's what happened to the Statue Of Liberty. Many of the iron supports had to be replaced.

However, if the cast iron cookware is well seasoned, that will not happen. The seasoned coating is a dielectric, preventing galvanic action from taking place.

dcarch

After 100 years the iron bands holding the copper skin to Miss Liberty were found to have some corrosion, partly due to galvanic action but more due to the exposure to salt spray. The copper skin was found to be eroded in a microscopic amount so, except for the torch it was left for another hundred years.
While anyone with a high school education knows about galvanic action, it had no bearing at all on the original poster's question. "Will it kill someone or the pan to put some tomatoes in with the braised kale"...\
The answers were no it won't hurt at all....even if you do stir it with a copper spoon (un likely to the point of silliness)you still won't materially hurt your pan or anyone who eats the kale.
This has no relationship to the fact that the iron bands holding the copper on the Statue of Liberty needed to be replaced after 100 years of exposure to salt air.

Posted by LindaC, "------This has no relationship to the fact that the iron bands holding the copper on the Statue of Liberty needed to be replaced after 100 years of exposure to salt air.----------"

You are probably correct, but only partially.

I had a good friend who worked for the architectural firm Swanke Hayden & Connell, who was engaged to perform the renovation of the Statue Of Liberty. I was able to visit the construction site many times with my friend, as a result, I had first hand knowledge as to the kind of damages which needed to be remedied.

Also, the follow from Wiki:

"------ A rather more spectacular example occurred in the Statue of Liberty when regular maintenance in the 1980s showed that galvanic corrosion had taken place between the outer copper skin and the wrought iron support structure.---"

dcarch

Thanks everyone! I'll make sure the Statue of Liberty gets no where near my cast iron pan of Kale, especially not with a copper spoon, or even a copper finger...

Steve

One thing to mention is you can store acid foods in enamel cast iron. Le Creuset, Lodge, and Staub are the most recognized. Bare cast iron is great for cooking, but storing acid foods will not only destroy the seasoning but you're food will have that metallic taste.

Here is a link that might be useful: Enamel Cast Iron

Steve, the thing that happens is that the acidity of the food leaches some of the iron out of the pan. it will actually increase your iron level if you do it enough, beneficial for many women who are anemic, BTW. I didn't know that until I had my iron checked a couple of years ago and it was high. So high the doc checked again. Then he questioned me and found my propensity for making things like chili in a cast iron dutch oven.

It's not harmful and I didn't find it seriously compromised the seasoning of the skillet either, but it can cause an "off" metallic kind of taste. I didn't notice it in things like chili, which had strong flavors of its own.

Annie