Is ‘Oven Canning’ Safe?
6 min read
When learning to can there are certain safety measures we all need to know about to make sure you, (or those around you) do not become injured, sick or seriously scarred. We learn these safety measures through research, manuals, and other canners’ experiences. In this article I am going to give you a sensible argument about why it is unsafe to oven can and why it could be considered an impractical way to store dry goods. We will also discuss alternative methods to storing your dry goods.
Is Dry Oven Canning Safe?
The answer is NO. As Wise Geek so elegantly explains this…
Oven canning is not safe because it is a dry heat and the jars are not made for that. They can explode. Contamination is the main fear when it comes to dry canning. In order for food to be shelf-stable, it must be heated to a hot enough temperature that any latent bacteria in the food is killed off. The premise behind dry canning is usually sound, as a 200°F oven is generally hot enough to be considered sterile. Not all oven thermometers are accurate, however, and it can be tough for home cooks to know whether the external temperature is actually penetrating the jars.
There is no way for cooks to test the internal jar temperature without removing the lids and compromising the food. Any bacteria that remains in sealed jars can grow into toxins over time, which can cause serious food poisoning once the contents is eventually consumed. Sometimes spoiled food looks discolored or has an unpleasant taste, but not always.
Then there is oil. Some of the few things that have oil in them are nuts and seeds and even some flours. The heat from the oven liquefies the oil making the product go rancid faster than if you had left it alone, which defeats the purpose.
Is it practical to use canning jars for dry good?
Lets pretend you have twenty, 1 pound bags of pinto beans and you want to store them air tight for long-term food storage. Right off the bat you’re going to have to buy, at minimum, two boxes of jars that run about $10-$15 each depending on where you live. (Assuming you do not have them already or have enough.) You will also have the added cost of using your electricity/gas to oven can your food. Depending on how often and how much you can, that can raise your monthly bills considerably.
If you already have a vacuum sealer machine, a 3- 20 foot rolls of bags cost approximately $26.50, however, you will be able to seal and store much more. Something else you might consider is instead of using the jars and the space they take up dry canning, use them for canning meat items and things you can not otherwise vacuum seal (Mmmmm, like salsa). If you insist on storing your dry goods in jars then the safest and cheapest way to go would be to use an Oxygen Absorber in the jar and then use a vacuum seal jar attachment to remove air and seal the jar tightly. If you do not have a vacuum sealer you can still add an Oxygen Absorber and then listen for the *ping* sound we all love about 15 minutes after you tighten the ring. The three most dangerous things you can do to your food storage is expose them to heat, light and moisture. So why expose your food to heat if you don’t have to?
In our home we use storage totes and five gallon buckets to store our dry goods. When we vacuum seal the food in the bags we pack them tightly in a storage tote and once full we place the lid on them and stack them up. I love how light the tote is (depending on the food of course) compared to stacking and moving jars. We typically use the vacuum sealer for items like crackers, drink mixes, tea bags, dried herbs, coffee, etc. For things such as rice, beans, flour, and sugar we use the five gallon buckets with Mylar bags.
As you can see, Dry Oven Canning can be more expensive, take up more space and can be very dangerous, as with any canning that does not practice safe, tried and true practices. Keep your family safe and stick to methods that have been tested and proven safe. One of my favorite quotes: Past performance does not guarantee future results.
Keepin It Spicy,
Cari Schofield aka Jalapeño Gal
Some more facts on Botulism and the dangers of unsafe canning practices.
What Research Means
Water bath canning and pressure canning have a higher degree of safety and reliability than dry oven canning. Both styles of canning have been tested, ‘researched’ and if done correctly is safe every time. Food storage is about storing your food safely for you and your family to use in hard times. Medical care may be scarce, getting sick from home canned food is not an option when hard times hit. Food borne illnesses can be mild and sometimes more serious, resulting in death without immediate care.
What is the Meaning of “Research-Based”?
Home canning has changed greatly in the 170 years since it was introduced as a way to preserve foods. Scientists have found ways to produce safer, higher quality products. Too many times people don’t understand there are risks when processing food at home. Those risks include botulism poisoning, which can lead to illness and even death.The development of a canning recipe is an extensive process. It involves repeating the entire preparation and canning process 15-30 times to obtain accurate heat penetration data. Then, microorganisms are put into the jars before processing to make sure the processing time is sufficient to destroy them. This research must take place in a laboratory with equipment for testing heat penetration and microbiology. This is why processing times cannot be made up! It’s also why a sealed jar does not mean it’s a safe jar.
I have heard a lot of home canners dismiss the USDA as if it is some governmental agency who only tells us certain canning practices are unsafe so we can’t do it and that is simply not true. The CDC reports:
In the United States, an average of 145 cases are reported each year. Of these, approximately 15% are food borne, 65% are infant botulism, and 20% are wound. Adult intestinal colonization and iatrogenic botulism also occur, but rarely. Outbreaks of food borne botulism involving two or more persons occur most years and are usually caused by home-canned foods.
Printable Download: Botulism Manual, please refer to page 7.
According to the manual, prior to 1950, there wasn’t wide-spread access to ventilators so people died if they contracted the poison before the anti toxin could be administered. After the 1950’s, people could go to the hospital and be put on a ventilator immediately giving them time to administer the anti toxin which decreased the number of deaths dramatically. In a SHTF world or long term emergency such as Hurricane Katrina/Sandy, there may not be access to medical institutions like there are now, so people will either die or live with the severe effects of the poisoning which include; muscle paralysis, double or blurred vision, dry mouth, droopy eyelids, slurred speech, difficulty swallowing and muscle weakness.
More Stories on botulism related deaths in the last 45 years:
This is the first I have EVER heard of this technique.
I agree, oven canning is not safe ( I see it pushed all the time for nuts) but I disagree with their cost and safety analysis of how to keep dry goods in jars on your shelf. You can often get canning jars for free and I’ve had things last for quite some time in jars on my shelves (dry beans, flours, additives, sweeteners, etc.) My kitchen is set up for it and we do it exclusively for all of our dry goods
Great article! Love seeing the truth published and sources cited. This practice is so silly – with all the other safer, easier, and cheaper alternatives available. Seriously – what could be easier than adding an oxygen absorber to your dry goods?! Thanks JG!
Thanks Stephanie!!
JG
I don’t think she meant storing them in jars wasn’t cost effective. I think she meant oven canning them wasn’t cost effective because of the time and amount of electricity used to dry can them versus just using an oxygen absorber. Of course if your storing a large amount of beans or flour its probably more cost effective to store them in five gallon buckets and Mylar bags.
Correct 🙂
I think she was suggesting a vacuum bag vs. canning jars…it’s just my opinion, but it’s good to also look at the feasibility of every storage method. If I had no electricity, those canning jars become a lot more useful than a roll of plastic! 🙂
Do oxygen absorbers kill bugs such as weevils in long term bean and corn storage?
Yes as long as the right size are used. Most living creatures can not live with out air.
GREAT article!
thanks!!
You can seal mylar up with oxygen absorbers without electricity no problem. It’s lighter and more mobile than jars. You can also reuse mylar bags as long as they haven’t been punctured. But it doesn’t have that rustic ‘cutesy’ look a lot of people like about the jars and when mylar compresses it will crush delicate herbs, or apple chips so it really just depends on your preference. If we stored all of our dehydrated and dry goods in jars we’d be over-run with jars so most of it goes in Mylar bags then into 5 gallon buckets.
Amen to that Stephanie!!
I have oven canned beans, flour and cornmeal and they turned out fine. Countryside had an awesome article about oven canning and it informs you of what you can and shouldn’t oven can. I will definitely oven can more. I also have a foodsaver with attachments for sealing jars and use it frequently.
Why would you waste time and money oven canning when you can add an Oxygen absorber and use your vacuum sealer to seal the jar?
JG
To seal mylar, you need heat. Do you have an iron that you stick in a fire? Maybe buying an old old iron is a good idea.
Most people I know have electricity, but you are correct if we are in a grid down situation you would need something you could heat over a fire to re-seal any Mylar bags you would need to re seal.
In regards to these particular meals though, when sealing in a mylar bag I would hope one would just use the smaller bags made for meals verses the five gallon buckets size. That way they can simply throw them away or reuse them for something else if they choose. We use a flat iron to seal our mylar bags.
JG
Thanks for the interesting article Jalapeno Gal! Never would have thought of the risks myself
You’re very welcome!
Someone ask Jackie clay if it’s safe she will tell you the truth.
I’ve never had a jar “explode” while dry canning but I have had them explode in my canner.
Just because something has not happened yet doesn’t mean it won’t. No matter what methods you use safety should always come first.
The premise behind dry canning is usually sound, as a 200°F oven is generally hot enough to be considered sterile. Not all oven thermometers are accurate, however, and it can be tough for home cooks to know whether the external temperature is actually penetrating the jars. There is no way for cooks to test the internal jar temperature without removing the lids and compromising the food. Any bacteria that remains in sealed jars can grow into toxins over time, which can cause serious food poisoning once the contents is eventually consumed. Sometimes spoiled food looks discolored or has an unpleasant taste, but not always.
Past performance does not guarantee future results.
I use all the methods above to preserve food. I only use the oven method for dry beans, flour, pasta, etc. My intent is to kill the little bugs that like to ruin our dry goods. The dry beans, flour, pasta, and etc. are all going to be heated up and cooked in a recipe. I would just like my staples to last longer than they would if not treated to oven canning. I also don’t put lids on the jars until after they are removed from the oven. Then I vacuum seal the lids with my trusty vacuum sealer.
Interesting article, I suppose I will have to slow down on my canning, I have quite the stock build up I almost feel silly for it now.. It also states over canning as being a silly practice in this book i just read I actually just did a review on it, it teaches you how to survive an impending EMP attack, it was such a good read and i can honestly say I’m prepared for anything now. you can check it out here if you’d like!
http://eyeopeningreviews.com/survive-the-inevitable/
I have heard of oven canning methods before, and I’ve done some research on why it isn’t considered safe by the USDA. The reasoning has to do with the ability of the heating medium, air in this case, to conduct heat into the substance you are trying to preserve. Air has a very poor ability to conduct heat. As an example of this, double pane insulated Windows use an air gap to provide a thermal insulative value. Nowadays the gap is filled with inert gasses like argon because their larger molecules will not leak through the glass as easily. When canning in a water bath or pressure canner the heating medium is with water or steam. Water has approximately 17 times (I believe) greater conductivity than air. The USDA uses the time tables recommended for safe canning based on this factor. When oven canning, in order to be certain of complete heat through, the times would have to be increased to account for the difference in conductivity of the heating medium. The times required to achieve these results are drastically longer and are not feasible due to fuel and time cost and limitations. So, in order for oven canning to be safely accomplished, you would need to multiply the canner process time by at least 17. It can be safely done, but it’s a huge waste of time and fuel to achieve safe results. If I’m incorrect on any of this please correct me. I won’t take it personal.
You are definitely correct in most of what you say. It is also my understanding however that the glass is not made to withstand dry heat. (oven heat) I have had jars break in the canners as well but I think the big difference is it is contained instead of being aloud to shatter or possibly *blow up* so to speak in a way that can be harmful to the person. Thank you so much for your input to this article. It is much appreciated. 🙂
We have been oven canning for awhile now. I never heard of oven canning the way it is described in this article. We do not put the lids on the jars until they come out of the oven. We do not use oxygen absorbers either. When we take each jar out of the oven (one-by-one) we take a damp cloth and rub the edge of the jar top, then place a hot soaked lid onto the jar and tighten it down (we wipe dry the lid before we place it on the jar — the seal has been heated by hot water). The jars lids pop as they cool. So far, none of them have lost their seal, and there is still no moisture in the jars. So far, we have done about 50 cases of quart jars. I check them every 6-months or so. We have never had a jar break or explode. I have tried to vacuum seal beans and such in the past without success. The vacuum seal bags “always” allow in air after about 6 months. Oven canning, for us, is much cheaper than buying dry goods from prepper food stores — by at least 1/3 of the price. I would recommend oven canning, if it is done the right way, to everyone.
I am not sure what you mean here. When food is canned the seal has to be on when it is heated so the food is at the correct temperature to kill germs and bacteria inside the jar before it seals. By removing the heat source before it is sealed that allows air and bacteria back into the jar. As far as dry oven canning (what the article is about) The safety issue is mostly in the fact that the jars are not made to withstand dry heat. It can cause damage to the jars, cracks, breaks and even explode in the oven. I am happy you have not had this happen yet but please no that is can happen. This article is just warning people it can happen, how and why. Please be safe in all your canning practices. Please also feel free to read what the national center for home food preservation says on the issue as well. There is a questions that says ” Is it safe to process food in the oven?” IT explains it well. http://nchfp.uga.edu/questions/FAQ_canning.html#7
I think he’s not really “canning” so to speak because canning involves either foods in a liquid or foods that are themselves liquid. The type of preservation Clif is performing is dry packing, but he’s using the heat of the oven to both kill insects and force air out of the container by making the air inside the jar take up more room because it expands when it is heated. When the lid is sealed on the volume of air inside the jar remains the same, but as it cools it takes up less room and forms a vacuum pulling the lid down. This type of preservation is safe because it’s a dry pack where there’s less than 12% moisture content, and the inside of the jar and its contents, since they are also surrounded by air are effectively heated to above 250° (assuming that is what temp he’s using). The problems associated with low acid canning are because there is more than 12% moisture content. There are a few environments that food can be stored long term safely, one is high moisture high acid (water bath canning), another is high moisture high temperature (pressure canning), and then the type Clif is doing low moisture, low oxygen. I use this method for preserving grain and beans, but I don’t prefer using mason jars for that because they are too small and too fragile. I use a Mylar bag inside of a five gallon bucket with oxy-absorbers and I seal the full bag shut with an iron and a level. Clif, I don’t know why you’ve chosen to use that method, but you may consider changing over to the method I use. You don’t have to heat dry food to make it safe to store long term. Dry foods are affected by insects which are killed by the absence of oxygen. Seal them in and let the oxy-absorber kill them. If you have a specific reason to use that method, by all means, go ahead, but it seems much too tedious to me.
Very well said. I myself use the mylar bag method for my dry goods. I also put my sealed bags in a five gallon bucket so rodent can’t get to it. 🙂
One thing to be aware of is that some creatures can still chew through the plastic buckets. We were storing bird seed in a plastic bug (no Mylar bag) and squirrels chewed a hole through it. I’m sure rats could too. If you are using plastic buckets make sure that you get all of the food into the Mylar bag and if any spills around it next to the bucket get all of that food cleaned up out of the bucket rather than leaving it in there. The Mylar keeps the smell sealed shut, so you are not attracting hungry animals. I also set up some mouse traps around my food storage room so that if they do go in there they will eat the peanut butter on the trap and hopefully get caught in it. I store beans, peas, and grains in Mylar bags in plastic buckets and have never lost any food to rodents or animal, just the bird seed.
There are some foods that cannot be stored for a long time, no matter how they are stored. Nuts and brown rice are two of those foods. We should all research foods and storage methods in depth before trying anything new. Some methods may feel more comfortable for you right now; but, if you do some experimenting over a period of time, you may be able to save yourself a lot of trouble and money in the future.
You are absolutely correct!!