I’m planning to can a bunch of tomato sauce this year, and I’ve heard that I should use a stainless steel pot instead of an aluminum one. Why is that? How do I tell the difference?
San Diego, California
Aluminum is not a good choice for cooking acidic foods (tomatoes, wine, citrus, chili, barbecue sauce, chutney, etc.). This is because aluminum is a reactive metal. When it reacts with the acid in tomatoes, for example, it can make them look duller and taste bitter, as well as possibly damage the cookware. Stainless steel is a good alternative to aluminum because it does not react to acidic foods, but it is more expensive and a poorer conductor of heat. To compensate for this drawback, cookware manufacturers often coat the underside of stainless steel pans with copper, or insert a layer of copper or aluminum just beneath the stainless steel surface. According to food science expert Harold McGee, these “hybrid pans are the closest thing we have to the ideal chemically inert but thermally responsive pan.”
Now to your question about how to tell the difference. Here are a few helpful indicators:
When tapped, aluminum sounds duller, and has less of a ring than stainless steel.
After being washed, aluminum tends to dull slightly, while stainless steel usually stays bright.
A brass key will scratch aluminum much more readily than it will stainless steel, because aluminum is softer.
— Tabitha Alterman, senior associate editor
Above: For making tomato sauce, the type of cookware you use matters. Photo by ISTOCKPHOTO/Daniel Gilby