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Jul 11, 2010 07:54 AM

Open Kettle Canning - Is it safe?

I only can tomatoes, and I always do them by processing the filled jars in boiling water.
I know someone who cooks the tomatoes, then packs them it hot, sterilized jars, and puts the seals on them at that point, Is this really safe? Will any potential bacteria be eliminated considering all the "open-ness" of the process?

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  1. Me again - I meant to write "then packs them IN (not "it") hot sterilized jars etc.

    1. All of what I've read (Ball, USDA, etc.) has said this is no longer considered a safe method. In addition, most resources seem to agree that tomatoes can no longer be canned as-is as a high acid item without a bit of added acid. So Ball, etc. all say to add some lemon juice when doing tomatoes.

      I'm sure other more knowledgeable home canners will have more/better information for you than I have.

      1 Reply
      1. re: LNG212

        I do add citric acid to the tomatoes before processing. I took a tomato-canning class through The Ohio State University Extension College, and I do exactly as I was taught.
        In regards to today's tomatoes being less acidic (see posts below), I agree that they are sweeter that when I was a kid. The tomatoes that I grow are supposedly an heirloom variety that was kept going by some nuns, and has been down passed through friends and relatives. Whatever they are, they are the meatiest, reddest and most delicious I have ever had. I save the seeds from year to year, and they always are the same, so I know they are not a hybrid.

      2. I started canning back in the 70s. At the time I did open canning of tomatoes. I also added things like celery, onions and peppers that lowered the pH even more. They were always delicious. No one died.

        Then I didn't can for a long while. When I got a garden and started again, Ball and everyone else had gotten much more conservative about the whole thing. I did too.

        It's not that I wouldn't like to be more free about the whole business or that generations of my family didn't eat home canned food. Hell's bells! I had family in Maine who wouldn't have had a vegetable for 8 months of the year if it weren't for canning with the available methods (which included simple parafin wax topping their jams). And they all lived to ripe old ages. But I am not a chemist. I don't really understand all of the complex biology of creating a nutritious environment and then excluding things that would like to survive in it and compromise the food I feed or give to others. So I follow the more conservative methods now recommended.

        It's OK. They're still good. And as an alternative you can roast tomatoes and freeze them in vacuum sealed packages. You won't get "meaty" tomatoes but you'll get some awesome base for soups and stews, etc. And you'll enjoy that special flavor in the off season.

        4 Replies
        1. re: rainey

          Yes, I too thought of the "generations" who canned previously and lived to tell about it when I was reading up on stuff. But one of the most interesting things I learned in doing some reading on the subject -- and why Ball/etc. changed their recommendations -- was precisely about tomatoes. Apparently tomatoes have changed *a lot* over the years. Because of the American sweet tooth, growers, seed makers (not sure what you call those people), etc. have gradually over the years changed tomatoes to lower the acid level in them from that of, say, our grandparents's time. And that has made all the difference.

          Personally, I found this absolutely fascinating and I learned a lot about US ag history just in trying to learn about safe canning.

          1. re: LNG212

            That's interesting. Thanks for that! It makes good sense. The tomato on most American tables today scarcely resembles the ones we had easy access to in the 60s and 70s. We all know what they've lost in flavor and gained in "sturdiness"!

            Perhaps what you're saying suggests that those of us who grow or have access to heirloom varieties would still be safe fresh packing our tomatoes. I know when I've done pans of roasted tomatoes or peeled a lot of tomatoes my hands can feel the acid after handling, say, the 10th one. Maybe there is some sort of pH testing such as a pool water testing kit that would give contemporary Americans a reasonable way to know if they're using tomatoes with adequate acidity? After all, I wonder if the people who are interested in canning today are the people who are buying the tomatoes that get shipped 20-30 layers deep in trucks. Still, publishers like Ball have to factor in what's most available when handing out advice as critical as managing potential toxins.

            Thanks for making good sense of an important question!

            1. re: rainey

              I totally agree about the tomatoes being different -- I remember those ones in the 70s when I was a kid picking them in my parents's garden.

              I also wonder about the long-shipped tomatoes vs. the ones from, say, our local farmers. But I guess I'm very conservative on this point. I'd rather add a tbs of lemon juice for safety then take the risk. I hot packed my tomatoes (with the lemon) last summer and really thought they were terrific during the winter. We made soup, sauce, etc. and frankly I don't think I ever noticed the lemon.

              And a pool pH kit - now that's an interesting idea!

              1. re: LNG212

                I live in CA and when you drive up and down the 5 through the Central Valley you can see the open trucks they haul tomatoes in. It's a revelation! You may look at a conventional supermarket tomato today and read that they've been bred with shipping in mind. But when you see those trucks -- which are like huge bathtubs on wheels -- with tomatoes loaded in 5'-6' deep you really get a sense of why what they taste and cook like are of marginal consideration to the growers who set the standards for what's available even as seeds.

                The only way to go today is to grow your own or find a local heirloom grower!

        2. I have a question about "open" canning.

          Does that mean you fill the steilized jars with hot tomato product, seal the jar and then process in simmering water?

          Or does it mean filling the hot jars with hot tomatoes, sealing and no further cooking/processing? Sometimes I've had the jars "pop" indicating they are sealed at this point, but I've always continued on with the processing bath in the simmering water.

          I do the former all the time, usually salsa which includes vinegar in the recipe.

          5 Replies
          1. re: John E.

            It is the latter. The simmering water method is waterbath canning.

            1. re: John E.

              Then there was fresh-pack which was stuffing in as many prepared tomatoes (cored, peeled or not, whole or quartered) as you could in a jar, pouring over some hot water to the headspace and water bathing. Those were the most like fresh tomatoes in flavor and texture. Verboten today but I'm rethinking it after my discussion with LNG and my assurance that I'm growing old, reliable varieties.

              1. re: rainey

                My parents used to can tomatoes in the manner you describe as fresh-pack., although I believe they also added a tablespoon of salt. Is it not ok to do it today because of less acidic tomatoes or simply because attitudes about canning safety have grown more conservative?

                1. re: John E.

                  Both actually. I think attitudes have become more conservative about food safety overall (at least here in the US). AND the tomatoes are less acidic -- unless you know the acidity level of your own seeds/etc., as mentioned above.

                  I follow the Ball book for whole peeled tomatoes and I've had really good product. This adds both salt (as you mention) and a bit of lemon juice to ensure acid level.

                  1. re: John E.

                    Salt, sugar, acid and heat are the ways to inhibit the growth of toxins.

                    As I said before I am NOT a chemist and I am NOT a biologist so I follow the more conservative contemporary methods. But, since I grow the old more acidic varieties of tomatoes I am thinking about investigating methods to assure myself that I have an acidic enough environment and using less processing.

                    I would NOT advise anyone else to do that without assuring themselves of adequate hygiene and reading to know that they were taking a well-calculated risk.