Canning: Oven vs. Water-Bath

[natalie martinkus]

I have been water-bath canning for the last 5 years. Last year my mom (also an avid canner) told me that she used her oven instead of the water-bath to seal her jars, and it worked perfectly. I tried it, and it worked great for me too! I just set my oven to 220 degrees (water boils at 212 degrees), and put the jars in for the time shown in the recipes, and added 5 minutes just to be on the safe side.

I have read in literature that one should not use the oven to seal jars, but I can't figure out the reasoning behind it. It was so nice not having a hot, steamy kitchen and a dangerous large pot of boiling water near my kids.

I would appreciate any insight you can give!

natalie

[Rachel Hoff]

There is a reason behind the boiling water. Because the jars are submerged at least an inch under the water's surface and air is lighter than water it forces more air out of the jars compared to jars  that aren't submerged. The water bath isn't just for sealing, but for also reducing oxygen, which helps inhibit mold. Also, hot air isn't nearly as effective at heating liquid, which is why we don't boil water in the oven. 

[Kathy]

I don't want to step on anybody's toes here BUT-
Here are some reasons for NOT canning this old timey way:

" As much as I deviate from modern canning recommendations, what they are advocating in that link is not a good idea unless they are only canning things that are boiling or hotter all the way through like jellies.

Setting the oven at 220 and expecting it to bring things to the temp necessary all the way through the jar only 5 minutes longer than it takes water to do the same job is just not going to work. Physics won't allow it since dry air does not conduct heat well at all. 

Old style oven canning took a long time to process. — it has not been recommended by anyone since WWII or so as a safe method of canning — 
I hope this helps you reconsider this method!  

[natalie martinkus]

That is an interesting point. However, every recipe I use calls for the jam/brine/syrup to be boiling or super hot when it is put into the jars to be canned. "Molds and yeasts are easily destroyed at temperatures between 140 degrees and 190 degrees. Salmonella is destroyed at 140 degrees. Staph is destroyed if food is kept above 140 degrees. Botulism is readily destroyed by boiling (read: temp at least 212 degrees) for high acid foods." Ball Blue Book of Preserving, 2006 (Sorry, Im in grad school so documentation is now becoming ingrained in me.)

Aside from cucumbers, which are the only fruit/veggie that is not heated through before being put in jars, I would assume the fruit + liquid for jams and preserves is already close to 212 degrees when it is put in the oven.

This summer, I may actually do a little experiment and take the temp of the syrup or jam when it is put in the jars to determine how close it is to 212 before it goes in the oven or water bath. After the set amount of time plus the 5-10 minutes which I add systematically for oven canning, I'll take the jars out and take the internal temp of at least one of the jars to see if it is above 212.

Kathy, can you please re-post the link that you reference in your post? It didn't come through.

Thanks so much for the comments!

Kathy said:

I don't want to step on anybody's toes here BUT-
Here are some reasons for NOT canning this old timey way:

" As much as I deviate from modern canning recommendations, what they are advocating in that link is not a good idea unless they are only canning things that are boiling or hotter all the way through like jellies.

Setting the oven at 220 and expecting it to bring things to the temp necessary all the way through the jar only 5 minutes longer than it takes water to do the same job is just not going to work. Physics won't allow it since dry air does not conduct heat well at all. 

Old style oven canning took a long time to process. — it has not been recommended by anyone since WWII or so as a safe method of canning — 
I hope this helps you reconsider this method!  

[Rachel Hoff]

I have to admit that in my first year of canning I used some old recipes that didn't require water bath canning for preserves/jams. They did require putting the preserves in while boiling and the sterilized jars did seal. Unfortunately, nearly all of the preserves that I didn't eat right away developed mold on them while still keeping the seal. I don't go without water bath canning now. 

I think it important to note that modern canning recommendations (which don't include oven canning) were developed for a specific reason and have been thoroughly tested in laboratories. 

[Kathy]

Natalie - Don't be sorry for wanting documentation!!  'Tis a very good thing! I wish more people would!! I myself am becoming quite anal about it! :)
The "link" was this site and your post. Sorry for the confusion - somebody had found your post and posted the link to it on another site and had a questions about the process and this comment explained it much better than I could so I just copied it to here.
I will try to clarify further- You are correct in the correlation of temps and the death of all the spoiling buggies. What is not mentioned is the time it takes for the *whole - to the center of* the produce/product to reach AND MAINTAIN the correct temps for the correct time to properly kill all the organisms that can spoil the food or your life! I was taught to respect proper processes because -as it was explained to me - Botulism - if you live, leaves you needing an Iron Lung! And that right there is enough to keep me not pushing the window on what is safe or proven to be unsafe.
My reason for replying is this - there are a lot of newbies that will read your post and think "anything goes". And I just don't want anybody to be harmed because they think if it is 'posted on this site',  it must be okay. 
Dos that explain my concern better?

natalie martinkus said:

That is an interesting point. However, every recipe I use calls for the jam/brine/syrup to be boiling or super hot when it is put into the jars to be canned. "Molds and yeasts are easily destroyed at temperatures between 140 degrees and 190 degrees. Salmonella is destroyed at 140 degrees. Staph is destroyed if food is kept above 140 degrees. Botulism is readily destroyed by boiling (read: temp at least 212 degrees) for high acid foods." Ball Blue Book of Preserving, 2006 (Sorry, Im in grad school so documentation is now becoming ingrained in me.)

Aside from cucumbers, which are the only fruit/veggie that is not heated through before being put in jars, I would assume the fruit + liquid for jams and preserves is already close to 212 degrees when it is put in the oven.

This summer, I may actually do a little experiment and take the temp of the syrup or jam when it is put in the jars to determine how close it is to 212 before it goes in the oven or water bath. After the set amount of time plus the 5-10 minutes which I add systematically for oven canning, I'll take the jars out and take the internal temp of at least one of the jars to see if it is above 212.

Kathy, can you please re-post the link that you reference in your post? It didn't come through.

Thanks so much for the comments!

Kathy said:

I don't want to step on anybody's toes here BUT-
Here are some reasons for NOT canning this old timey way:

" As much as I deviate from modern canning recommendations, what they are advocating in that link is not a good idea unless they are only canning things that are boiling or hotter all the way through like jellies.

Setting the oven at 220 and expecting it to bring things to the temp necessary all the way through the jar only 5 minutes longer than it takes water to do the same job is just not going to work. Physics won't allow it since dry air does not conduct heat well at all. 

Old style oven canning took a long time to process. — it has not been recommended by anyone since WWII or so as a safe method of canning — 
I hope this helps you reconsider this method!  

[Kathy]

Great answer Rachel! Thanks!

Rachel said:

There is a reason behind the boiling water. Because the jars are submerged at least an inch under the water's surface and air is lighter than water it forces more air out of the jars compared to jars  that aren't submerged. The water bath isn't just for sealing, but for also reducing oxygen, which helps inhibit mold. Also, hot air isn't nearly as effective at heating liquid, which is why we don't boil water in the oven. 

[Kathy]

Rachel- I too 'learned' some unsafe ways and had similar results! And yes even the pickles get processed now!

[natalie martinkus]

Thanks for the reply, Kathy. You make a very good point about the amount of time it takes to kills the bugs once at the correct internal temperature. My friend and I write a blog, and have been posting about our use of the oven method. I was thinking that we do need to put a disclaimer on our posts stating that it is not the nationally recognized way to preserve. I don't want anyone to get food poisoning because they dont understand the principles behind canning, and assume that our "oven" method is just a shortcut. I guess I will have to go back to water-bath canning.

[Kathy]

Natalie you are welcome and the disclaimer - Thank you!! That would be awesome!
And as for JUST WB canning -Now that we have it cleared up -
I DID use my oven to 'dry can' peanuts! It was GREAT! Technically, a food saver- vac attachment would have preserved the same,  I  think!  I didn't have one at the time I needed to preserve the peanuts! 

I was able to hold off from eating the last jar for a few years!! :) And  they tasted wonderful! I don't remember all the particulars, but I could find it again if I ever came across a great deal on nuts! :) So don't drop the oven canning too quick! It does have a purpose! :)

[HOMEGROWN.org]

We posted a link to this discussion on the HOMEGROWN.org Facebook page and it caused quite the stir!

• • 

    Shannyn Beattyin Octobers issue of Countryside magazine there was an article about canning dry goods in a hot oven. it was very interesting!

    Yesterday at 9:07am ·
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    Christene Catlini am curious to the why not's also having a toddler running around this would help me and it would seem to be able to do more at one time.

    Yesterday at 9:08am ·
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    Rural SpinIt would depend upon what I was canning. And since I live at high altitude, I'd have to be especially careful since temperature/pressure does funky things up here (there are known standardizations for high-altitude water bath and pressure canning, but none for oven canning that I know of).

    Yesterday at 9:10am ·
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    Aramenda PerryWould love to know if there are any major concerns with this method.

    Yesterday at 9:12am ·
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    Deanne N John FishThis is just one more example of why I am leary of eating most people's home canned food. My rule is: If it's not in the Ball Blue Book, it is not safe. There are a lot of things worth passing down from one generation to the next, and canning in the oven is not one of them. Please don't take the chances when it comes to home canning, and if you do, please don't feed it to others.

    Yesterday at 9:31am ·
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    George GobbleI would like to know also if this is a safe way to can...sounds like an easier way to can.

    23 hours ago ·
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    Kelsy StarSounds like a good way to break your jars. Air conducts heat much less efficiently than water, so I'm not sure whether the food would get heated thoroughly for long enough.

    23 hours ago ·
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    Carol SullivanI have done applesauce in the oven in jars, but Kelsy's comment, just above mine, does bring to mind some doubts. Good point.

    23 hours ago ·
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    Jeanne SutterI've just done a quick search through my materials and haven't found anything specific, yet. My best guess is that the hot water bath creates a vacuum which draws the air out of the jars and properly seals them. While the oven *may* be hot enough to reach boiling temp, it would be difficult to regulate. I understand the appeal of oven canning but I would not feel comfortable recommending it. Also, should a jar explode, it would be much messier to clean up than in a hot water bath. Stick with USDA/Blue Ball book recommendations and use your oven for drying as a food preservation method. Happy canning!

    23 hours ago ·
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    Rachel HoffThere is a reason behind the boiling water. Because the jars are submerged at least an inch under the water's surface and air is lighter than water it forces more air out of the jars compared to jars that aren't submerged. The water bath isn't just for sealing, but for also reducing oxygen, which helps inhibit mold. Also, hot air isn't nearly as effective at heating liquid, which is why we don't boil water in the oven.

    23 hours ago ·
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    Happy HallowToday, Vegetables are not what so many of them used to be. Acid level is lower in some of the tomatoes and we are adding lemon juice or vinegar to bring up the acidity. Personally, I would not try this. The oven canning (Countryside Magazine) was for dried things and I have been using this method for dried vegetables and fruits. I was looking to have a longer shelf life than 3 or 4 months and this method works. If any of you are interested in this process I have used it and would be glad to share.

    23 hours ago ·
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    HOMEGROWN.orgHappy Hallow, by the response here, I would say there is great interest! Would you like to write an oven canning 101 for folks?

    22 hours ago ·
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    Jana FranzenThe one and only time I canned, I used the oven method. My pickles taste fine. (a little mushy, but I think that's cause I oversoaked 'em.)

    21 hours ago ·
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    Woodwife GreenIt's a risky method. Canning jars aren't made for oven use and you can't be sure that the proper temperature has penetrated evenly all the way through the filled jar.

    20 hours ago ·
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    Woodwife GreenFrom the NCHFP:
    "Is it safe to process food in the oven?
    No. This can be dangerous because the temperature will vary according to the accuracy of oven regulators and circulation of heat. Dry heat is very slow in penetrating into jars of food. Also, jars explode easily in the oven."
    
    http://nchfp.uga.edu/questions/FAQ_canning.html#7

    Expand Preview

    20 hours ago · ·
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    Happy HallowYes, I would be delighted to share what knowledge I have of oven canning with your readers.

    15 hours ago ·

And, as you can see, Happy Hallow did share her expertise in this member blog!

[Kathy]

Well, What is so confusing is they are calling it oven canning! When Happy Hollow is only vacuum sealing her foods in jars by the method of heating ! That just makes no sense to me. If the foods are dried - why heat them to the temps that will do what for the food? How is it any different than these same foods in a BWB or PC methods which uses all the energy to RE-Preserve these preserved-by-drying foods.
And those that actually canned foods in their ovens were questioning that method when presented with the facts. I just wished the two processes would have been differentiated ! Seemed people didn't read the reasons given and the dangers sited and still were interested in in just oven canning in general for all types besides just vacuum sealing dried foods! Seems like such a waste on so many fronts!

Thanks for sharing this!

[Bootsie Battle]

My reason for oven canning was because the suggested shelf life of my dried tomatoes was 3 to 4 months.  I had 5 quarts of tomatoes.  I wanted to have them last all winter.  I could have frozen them but I did not have the space in my freezer when I needed to make a decision.  This method was presented to me and the suggested shelf live is over 5 years.  Countryside article,  which I have looked up,  says 7 to 10 years.   I would never suggest this to be a replacement for the boiling water bath.  I am too lazy to clean the oven if a jar should break.  I have always used the suggested methods.  I raise all of the things I can at this time and I put to much work into getting the crop prepared to take a shortcut and may loose all of my hard work.  There are people taking chances with canning because they want a short cut and there are NO short cuts.  You cannot see botulism.  

 I would think you would bring the jars to a boil before filling them and if you follow the instructions they stay in the water until you fill them.  Return to the jars to the canner and bring to a boil.  I question why this would be a problem for anyone.  As you already have the canner with the water if you are canning correctly.  I do not know if they used the dish washer to sterilize the jars.   The waste of energy would be heating the oven at this time.

 You may feel I was wasting energy but I am still enjoying my tomatoes .  I am Not paying the price for a jar of  sun dried tomatoes in olive oil at the grocery store which is much more than what it cost me to process my tomatoes.  For me, it was a problem solved and I do not have a vacuum sealer.  

Thank you for your comments!