Whether you’re an expert canner, a beginner or someone who’s just contemplating dipping their toe into the home preservation waters, you’re certain to have heard that the only foods safe for water bath canning are the high acid ones. We define high acid as a food that’s got a pH of 4.6 or below (the lower the pH, the higher the acid content). The acid content of jams, preserved fruits, chutneys, pickles and more are our balm as canners, because it’s what keeps those preserves safe in their jars until you determine it’s time to crack them open.
There’s only one precaution that you must take when cooking these high acids foods into their canning-ready state. You’ve got to make sure you use a cooking vessel that is non-reactive. Pots made from metals like aluminum and untreated cast iron react with the acid in the preserves and can leach a metallic flavor into your final product. Shae at Hitchhiking to Heaven talks about an issue just like this in her most recent post in which she cooked high bush cranberries in a a cast iron skillet.
Note: The one exception here is when it comes to traditional copper preserving pans. Copper is a reactive metal, but when fruit and sugar are combined and cooked in a copper pan, the metallic flavor is not leached into the finished product. Once again, I refer you to Shae, and her post about copper pans.
Non-reactive pans are ones made of either stainless steel or enamel-lined cast iron (think Le Creuset or similarly enameled Dutch/French ovens). I recently acquired a low-and-wide 8 quart stainless steel All-Clad Stockpot that’s become my very favorite preserve-cooking pot. Its width means that the jam cooks down quickly and the stainless steel body allows me to scrub away when I accidentally let things overcook. We got it at Cookware & More, which is a kitchen wares outlet in Norristown, PA. They sell slightly irregular All-Clad products at a small discount, so if you’re in my area and in the market for some good cookware, you might want to consider checking them out (be warned though that it’s a strange store, tucked in the back of an anonymous industrial park in what feels like the middle of nowhere).
If you’ve got a stash of aluminum pots and want to give them some role in your canning process, you can always press the big ones into service as processing pots. The oval vessel you see in the picture at the top of this post is an old, aluminum pot I got in college at a thrift store. My mom and I have matching ones and we both find that it works nicely when we need to process a slew of half pint jars.