Kenny,

I did not know (probably because I don't have any aluminium pots) but I had to look it up. NOPE, don't use aluminium! Here is a blurb from about.com which is where I found the info:

Do not use an aluminum pot, pan or utensil when cooking tomatoes. The acid in the tomato reacts unfavorably with the aluminum. Using aluminum makes the cooked tomatoes more bitter and fades the color. The dish will also absorb some of the aluminum and the acid in the tomatoes can pit and discolor the aluminum cookware.

J.

That's what I've always heard too.

Thanks. Yesterday I was "cooking" up some to freeze and it just seemed that I should not be doing what I was doing. So next time I will not do what I was doing. I got a big stainless pot around here some where............
Kennyp

In general the best cookware to use is ceramic, iron and stainless steel. At least that's what I've read and it makes sense.