Today I faced my lifelong uneasiness about canning and prepared a plum-cardamom jam (from Canning for a New Generation). It is delicious and seems to have set up well. My concern is about the residue caused by the pot I used for sterilizing and processing. I used a pot intended for tamales. I had not cooked in it since I bought it (cheap) some time after Christmas. I assume it is aluminum -- it is light both weight and color. Before boiling in it, I washed it with soap and water, but I definitely took more care in cleaning the pot than its fitted rack.
After sterilizing the jars, I noticed the interior of the pot had turned dark, but I remembered this being the look of previous vaporeras I had used. When I took the sterilized jars out, there was a white film on them. Having come this far, I decided to just finish the job, ask about it on Chowhound, and chalk it up to canning practice if I was instructed to throw out the batch of jam.
Now that the filled jars are sitting next to clean, unused jars as they cool, the difference is striking. There is a white filmy residue on the filled jars. It wipes away, but I am concerned about how this has affected my jam inside.
I know better than to cook jam in an aluminum pot, but did I make a mistake in using aluminum for the boiling water? Is it just because the pot was new, and this should not happen again after a thorough cleaning? Is that little bit of residue inside the jars safe for consumption?