Canning 101: Why You Can’t Cook Acidic Foods in Reactive Pots

Sterilizing jars

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.

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35 Responses to Canning 101: Why You Can’t Cook Acidic Foods in Reactive Pots

  1. 1

    This is a bit creepy, boyfriend and I were having this EXACT conversation last night while standing over our Le Creuset, simmering some late Summer squash for pickling! He had a moment of panic when reading the recipe over again and seeing the ‘non-reactive’ bit, but I assured him that our Le Creuset was just fine…and now I have reinforcement!

  2. 2
    Casey DelliCarpini says:

    So, I have what I believe to be an old aluminum pot that I’ve been using for cooking just about EVERYthing. It has a larger sibling that I generally use as the water bath pot. I haven’t noticed that any of my canned items taste metallic. Is it because a) it’s been used so much that it has built up a nice little cooked/burned on coating? b) that my palate isn’t as good as I think it is and they DO taste metallic? or c) I don’t really know what aluminum is. (I’m hoping for A.) Thanks for this post!!

  3. 3
    Mary says:

    Is it possible it’s anodized aluminum? anodized aluminum is made specially to not get into the food you are cooking, but I don’t know if it can stand up to high acid foods (although I thought that was the point).

    Marisa, do you know if all this good info is just on untreated normal aluminum pots, or is it pertinent to all aluminum pots, whether anodized or not?

    Thanks.

    • 3.1
      Marisa says:

      Mary, anodized aluminum is sort of a different animal and should be fine. I was only talking about those old school, untreated aluminum pots.

      • Danni says:

        Ok… now define “old school.” Now I don’t know which aluminum pot is ok & which is not. lol

        • ben says:

          My understanding is that at least one study did not find leaching of aluminum into food, if the cooking surface is anodized. In fairness, I don’t think it has been studied extensively.

          If you go out to eat, your food may well be cooked in aluminum, and generally not anodized aluminum. The heat transfer is very good, and the pans are cheap to buy. Commercial cookware gets ridden hard, and the restaurant is judged by serving food “just right”, so you can see the appeal of aluminum. Of course, what you eat every so often is less harmful than your daily diet.

  4. 4
    meemsnyc says:

    Thanks for the great tip!

  5. 5
    amy says:

    I love your blog. I am new to canning and the like and i look forward to seeing your posts in my inbox. Thank you!

  6. 6
    Angela Utley says:

    My fave pot to use is my husband’s IKEA 365 Stockpot. It’s 12″ in diameter, 7″ tall, and holds 11 quarts. I have been using it all summer long without issue and with lots of great results.

  7. 7
    Cat K. says:

    What about pots with nonstick coating? My set of pans is Pampered Chef, and they’re hard-anodized aluminum with nonstick coating. I’ve been using my enameled cast iron, but it would be nice to have more options!

  8. 8

    i use an aluminum pot for processing, but i’ve found that i get a kind of chalky film on the outside of my jars when they dry. do you get the same from your aluminum pot?

  9. 9
    Marisa says:

    Cat, I don’t like to use non-stick cookware for jam making, but I think that’s more personal preference than scientific fact.

    Maltese Parakeet, I get that chalky film in any processing pot. It’s the minerals in your water. I’ve found that adding vinegar to the water bath can help prevent it.

  10. 10
    Krista says:

    I get that chalky film too and first time thought I hadn’t cleaned out my mom’s canner well enough, but discovered that yes, it was due to our hard water. Thanks for the tip on adding vinegar to my canning water, I use it in my washing machine, but hadn’t thought to use it in my canner!

  11. 11

    we do have really hard water. thanks for the tip!

  12. 12

    Marisa, thanks so much for the (double!) shout out. I think it’s great if folks can learn from my mistake with the iron-apple butter. As much as I’ve learned from investigating different kinds of metals for jam pans, I find that I still have some floating questions. One of them has to do with the cast iron:

    I wonder whether cast iron would behave the same as copper if the fruit were mixed with sugar before it is added to the pan. I cooked down raw cranberries in my cast iron pan (I know, I know) but I wonder what would have happened if they’d gone into the pan with the sugar. I bet the reaction would have been significantly less. Witness, for example, this gorgeous skillet jam offered by Dinner with Julie. I don’t think her cast iron skillet is coated, though it’s hard to tell for sure.

  13. 13
    Marisa says:

    Shae, was actually thinking about Julie’s skillet jam while I was writing that post and wondered something similar. I also wonder if it also has to do with the fact that strawberries have less acid than cranberries. Maybe? It’s the sort of thing I’d be excited to do some semi-scientific tests on, if only I had the time.

  14. 14
    Alison says:

    Thanks for the reassurance that my hard anodized aluminum is OK.

  15. 15

    Yes, I want to learn more about it, too. And I agree — there’s probably not much worse you could prep in a reactive pan than raw cranberries!

  16. 16

    [...] at Food In Jars explains why you can’t can with reactive [...]

  17. 17

    What about pots with nonstick coating? My set of pans is Pampered Chef, and they’re hard-anodized aluminum with nonstick coating. I’ve been using my enameled cast iron, but it would be nice to have more options.

  18. 18

    [...] non-reactive pot: read here for a great explanation of what that means from Food In [...]

  19. 19

    [...] Marisa at Food in Jars also wrote a piece of types of pans in 2010 that’s a great reference on non-reactive pans. [...]

  20. 20

    [...] is a Non-Reactive Pan, Reactive Pan vs Non-Reactive PanHealthy cookware | Eartheasy BlogCanning 101: Why You Can’t Cook Acidic Foods in Reactive Pots …Is Anodized Aluminum Cookware SafeChoosing Your Cookware So It Works For YouFood Science: Explaining [...]

  21. 21
    Kasey says:

    For years (since the late ’70s) I’ve been using a combination of a 42 pint stainless and 42 pint aluminum stock pot for cooking my tomatoes for canning. I often need that much capacity for a canning session. Being too dumb to know that I should not use reactive metal to cook the tomatoes, I just did it. At times, I have also used enamel lined pots and even my electric roaster. I have never noticed a difference between them in terms taste or quality of the finished product. In fact, I enjoyed some 2011 vintage juice this morning for breakfast…yummm!

  22. 22
    Charlene says:

    I found a pizza tray I thought would be ok so I tossed it into a large pot to keep jars off bottom. I first, sterilized the jars then boiled the filled jars in the same water. I used a separate non-reactive pot for the brine.
    Did I destroy the pickles?
    Do I need to throw away all of it or are they still edible? They’ve been in the cabinet since I made them because I noticed the pizza tray totally oxidized while boiling. Duh! :(

    • 22.1
      Marisa says:

      Your pickles are fine. You only want to avoid reactive cookware when you’re cooking the food. Once it’s in the jar, it won’t impact the quality of the finished product.

  23. 23
    cathy says:

    What type of pots are the magnalite?Cant find the answer on the net. That’ for fs what I use for beets and pickles.

  24. 24
    mlaiuppa says:

    What about ladles?

    My Mom has a vintage Wagner Ware aluminum ladle that is the perfect shape for pouring the jam into the jars. Will that little bit of exposure react with the jam or leave a metallic taste?

  25. 25
  26. 26
    Brian says:

    I made 16 quarts of apple sauce in a stainless steel pot which turned out great! Tonight I made another batch using the same batch of apples, however this time I used an anodized aluminum pot. The end result was significantly different. It had a distinctive taste that until this blog, I could not place. Now it is clear that it is a metallic taste. I wonder now if it should be dumped.

  27. 27
    Caren says:

    I always do all my canning with stain steel surface because from what i read, it seems to good as it is non reactive with most food items.

  28. 28

    […] of my strawberries in Martha’s hands and dove right in. I was at a loss at first, a “non-reactive pot“? What on God’s green earth was that? Would my Wal-Mart one suffice? Turns out at work […]

  29. 29
    Cindy Moore says:

    What about the really old enamel ware pans/pots? Mine are the white ones with the red trim around the rims. Some have chips on the outside but not the inside. Are these ok to cook my pickle brine in? I don’t have another really large pan? Just getting started. Only use these normally for my kitchen decorations only, have them hanging in my antique looking red & white kitchen???? Thanks, Cindy

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