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Apr 6, 2011 05:07 AM

Oven canning

Is it really unsafe? I have read warning after warning about it, but there is a very popular cook/gardener here in Denmark that has been demonstrating it on TV for years and I just wonder how she can get away with it if it really is so dangerous. It's on a public broadcasting channel, so I'd think they'd be alert to that kind of thing.

On the other hand, she's been canning in the oven for years, and sells tons of cookbooks describing the process. Several of my neighbors have canned everything from meat to tomatoes to fruit using the method. It sure looks easier than the hot water bath method, and cheaper than the pressure cooker method since I don't have the equipment, so I'm determined to find out the facts here. Anyone?

I apologize if this has been posted a bazillion times already--I did a search and didn't find it, though.

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  1. It boils down to this. Food science/research has provided us with information to reduce the incidence of food born illness. If you have read the warnings then you have read about uneven or insufficient heating, jar breakage and the necessity of canning low acid food in a pressure canner. Oven canning MAY work under some circumstances. There other circumstances where it is not safe. Water bath and pressure canning have a higher degree of safety in their respective applications. You either take advantage of what has been learned or not. It is all about reducing your odds of getting sick. Food born illness can be mild or result in death. The choice seems pretty easy to me, as I have seen the results of severe food born illness, but you will find plenty who have used less safe methods for years and say "nobody ever got sick".

    1. First: Canning in the oven should mean placing jars filled with food in a shallow container with WATER!. Second: THE safety factor is whether the lid SEALS!!. If the lid seals, the food is good. Third: Anytime a lid does not seal (using ANY method of canning), when the lid is removed the smell will be the undeniable clue. Period.

      3 Replies
      1. re: launicaliz

        "If the lid seals, the food is good."

        This is not true. The spores that can cause botulism grow only in the absence of oxygen in low-acid, moist environments. The reason for pressure canning is to heat low-acid food in the middle of the jar to a high enough temperature to kill the spores (higher than the boiling point of water). High acid foods should still be heating in a boiling water canner to kill other microorganisms. From the National Center for Home Food Preservation:

        "When ideal conditions exist for growth, the spores produce vegetative cells which multiply rapidly and may produce a deadly toxin within 3 to 4 days of growth in an environment consisting of:
        - a moist, low-acid food
        - a temperature between 40° and 120°F
        - less than 2 percent oxygen

        Botulinum spores are on most fresh food surfaces. Because they grow only in the absence of air, they are harmless on fresh foods."

        1. re: launicaliz

          "THE safety factor is whether the lid SEALS!!. If the lid seals, the food is good. "


          There is quite a bit more to canning safety than that. Obviously, unsealed cans shouldn't be stored/used. But a sealed container can still make you sick or even kill you. Offhand, I would think that a highly reliable, accurate oven could pasteurize jarred food. Which is not at all the same as sterilizing it. You'd probably be quite safe if you froze the jars after canning - but then what was the point of canning?

          Wekick said it right. Just because you can do something a few times (or even habitually) and not get sick doesn't mean it's safe. Botulism is nothing to fool around with.

          1. re: launicaliz

            Wow. All three points are wrong.

            Because an oven is not under pressure, that means the temperature of any water, either inside the oven or inside the jars, can never rise above 212F, which is not enough to kill the botulinum spores, which need a temp of at least 240F.

            The second point has already been addressed. WRT point three: Botulism is invisible, tasteless and odorless.

          2. For many years people always canned in ovens. NEVER once did anyone get sick. My guess when one gets sick from home canned foods the lids seal on could be from some type of chemical put into the food before canning.

            3 Replies
            1. re: rhondamike

              Who do you know who puts "chemicals" into their home-canned food?

              1. re: rhondamike

                I'd like to know what authority you have to make a declarative statement like this about the general use of oven canning?

                1. re: rhondamike

                  "NEVER once did anyone get sick."

                  Sorry, your information is wrong. My mother was haunted all her life by the death of a classmate, and the girl's entire family, from eating improperly home-canned food. The family had not been seen for several days, and somebody went to the house to check on them. All dead. Botulism.

                2. I pack sterilized jars with sterilized lids with cubed meat. Add tsp of salt and pepper. Fill a large cake pan half full of water. Twist rings down until it just begins to tighten. Too tight and air won't escape as air heats and expands breaking the jar. Place jars in the water bath. Bake in oven for4 hours at 250. If you need to add water to pan during baking, boil water before adding or you could cause jars to explode. After 4 hours turn off oven and allow to cool in the oven over night.

                  17 Replies
                  1. re: Tater62

                    You're begging for trouble. That process does not sterilize your cubed meat, and the pH is not low enough to prevent bacterial growth.

                    1. re: Tater62

                      Meat needs to be pressure canned. Oven canning isn't safe for even high acid foods but for low acid foods like meat, that's just crazy. I hope you are not feeding that to anyone.


                      1. re: rasputina

                        How do you explain the fact that my Grand parents,my Father and now myself have been doing meat this way every year since 1921? I'm 52 and have given away canned pints to everyone for 30 years. I've even eaten canned meat that was 3 years old. You must not have your jars or lids sterilized properly.

                        1. re: Tater62

                          You're messing with botulism. It's not going to get on meat very often, but it won't be killed by your method if it somehow does.

                          And it only takes once. We're not talking about a little nausea and vomiting where you feel better in a week.

                          1. re: cowboyardee

                            Do not confuse the term water bath with boiling jars in a water bath on the stove top because the temp only gets to 212 degrees at best.

                            Pressure canning is suggested to make sure the internal temperature reaches 240 degrees and then many suggest holding this temp for 10 - 90 minutes. Here's what the CDC says: "A pressure cooker must be used to can vegetables at home because it can reach temperatures above boiling, which is necessary to kill botulism spores".

                            In my family, we employ oven canning, where the internal temperature reaches 250 degrees and then maintained for 4 hours. Botulism does not respond to pressure, it responds to the fact that we are able to attain an internal meat temp of +212 degrees by oven in the same manner that a pressure cooker is able to attain 240 degrees under 10-14 lbs of pressure.
                            Chow for Now!

                            1. re: Tater62

                              sorry. if you've found a way to make liquid water reach temperatures above 212'F at atmospheric pressure, the Nobel Prize people would be interested in hearing from you.

                              your jars are not reaching 250'F or 240'F internal temperature.

                              you cite the CDC about using a pressure canner and yet ignore the CDC/FDA/USDA/FSIS comments stating that oven canning is inadequate.

                          2. re: Tater62

                            sterilizing whatever has nothing to do with it. you really should read up on this stuff before you do kill somebody. you are not following safe practices.

                            there were 420 billion rounds of ammunition fired in WW2; there were not 420 billion dead or wounded. so, sometimes you win, sometimes you lose. your number has simply not yet come up.

                            it takes 240'F to kill the botulism spore. the oven air temp setting of 250'F sounds good until you get to the water bath part. the water and the jar contents slightly above and all below the water level will never exceed the 212'F boiling point of water.

                            if the spores are there, and the pH is too high, you're in for a bad day....

                            1. re: PSRaT

                              I'm sorry, there must be a misunderstanding, I though I was clear on our technique. Our jars are sitting in a aluminum cake pan with about 1 inch of water in the bottom. About 3/4 of the jar is exposed to the 250 degrees oven temps, thus the heat radiates the heat to the bottom 1/4 of the jar, raising the temp of the contents above 212. As the heat evaporates our "water bath water" we add additional boiling water to the cake pan to prevent the jars from breaking as is the case when you add cold tap water to hot jars! 1 hour into the baking process we can see the contents boiling inside the jar.

                              1. re: Tater62

                                ..1 hour into the baking process we can see the contents boiling inside the jar.

                                so it's boiling at 212'F.

                                that's all the temperature you're going to get. science, physics and thermodynamics is actually real.

                                1. re: PSRaT

                                  Obviously you don't have a magic oven ;)

                              2. re: PSRaT

                                CDC says it it takes 212 degrees for 10 minutes to kill botulism, so what's your problem, at the very least my meats is exposed to 212 degrees for 4 HOURS, no one in my family was ever killed or sicken in the last 90 years. You must be a Pressure Cooker salesman.

                                1. re: Tater62

                                  CDC says it it takes 212 degrees for 10 minutes to kill botulism..

                                  can you cite the CDC reference for that?

                                  1. re: Tater62

                                    Check your CDC link again. At 212, it takes 10 minutes to denature the botulism toxin. The clostridium botulinum spores (bacteria) themselves are not killed until a temp of about 240 is reached and sustained. Denaturing the toxin and killing the bacteria that make the toxin are two different things.

                                    This means that anything boiled to 212 for 10 minutes will not give you botulism... if you eat it right then. But if you let it cool and give it time, the spores that were never killed by the heating process can still create more toxin.

                                    1. re: Tater62

                                      I agree tater. My mom canned everything boiled them outside in an old black wash pot . Green beans and more. We never got sick and nothing spoiled either.
                                      Raised 5 kids and fed everyone we knew....
                                      CDC has nothing to do except sit on their tails and if they don't come up with crap they have No jobs....

                                      1. re: Suzmoz

                                        It's difficult for me to understand why people are still trying to validate water bath canning for low-acid foods. I guess they enjoy the thrill of gambling.

                                        Gambling with botulism means you are playing with much, much higher odds than those available at Las Vegas or Atlantic City. It's an extremely rare disease, only 225 cases or so a year are reported in the United States. And if those sick folks are able to get themselves to medical care in time, there is antitoxin available to save their lives. Rehabilitation takes many months, with time on a respirator and other nasty details, but hey, you're still alive, right?

                                        Botulism SPORES have to be exposed to heat greater than 240 degrees Fahrenheit in order to destroy them.

                                        Botulism TOXIN (the waste product given off by the SPORES) can be killed at the boiling point of water, 212 degrees Fahrenheit. That is why home-canned food must be boiled in a pan on top of the stove before eating.

                                        So, no need to argue this further. If you like gambling with the odds, fine, go right ahead. If you don't mind putting your family members at a TINY risk, that's your business. But make sure your health insurance is paid up, and you've got 911 on speed dial, and you might want to check out the response times for EMS in your area.

                                        I'd say the reason the risk is tiny is because most people in the US are eating commercially canned products, which MUST be processed in a safe manner to achieve temperatures higher than 240 degrees, for the prescribed amount of time. And the majority of folks eating home canned foods are using stuff canned in a pressure canner. And hopefully, everyone is vigilant for the warning signs of spoilage: leaking seals, bulging lids, bad odors.

                                        Take your chances. For me, for my peace of mind, my life and the lives of my loved ones mean too much to me to take ANY chances at all. They are already at risk of too damned much by simply living in today's world. I'm not about to risk having them suffer from any botulism exposure.

                                        Oh, and if the person who does the home canning in the oven survives the botulism episode, the District Attorney may not be willing to accept the defense of, "Well, gee, my grandmother always did her canning in the oven and everyone was just fine!" This is the terminology the District Attorney will be using in that case: "Manslaughter is not as serious a crime as murder. On the other hand, it is not a justifiable or excusable killing for which little or no punishment is imposed."


                                        1. re: VOWeaver

                                          Last spring's botulism outbreak at an Ohio church, the one that killed a woman and hospitalized 23, was traced to home-canned potatoes.

                              3. re: Tater62

                                You're kidding, right? You'd PREFER to ignore decades of research, made available to you for free, to help you process your food safely? Gambling with your family's safety with botulism, an actual deadly toxin?