How Not To Die From Botulism: What Home Canners Need To Know About The World’s Most Deadly Toxin

You may have seen this article. A Seattle man recently contracted botulism from his improperly canned elk meat and is lucky to be alive. His description of how he canned the elk is like a checklist for everything you never, ever do when canning food.

I love to see so many new people taking up home food preservation, but you gotta do it right. I once gave a presentation about home canned convenience items and how to use them and, about a third of the way through the presentation, I just stopped. I could see something in the audience’s collective eye.

“Ok, how many people here don’t can because they are afraid they are going to kill their whole family with botulism if they do?” I asked.

Fully two-thirds of the audience raised their hands, so I embarked on a totally non-scripted, impromptu talk about what botulism is, why it’s a concern for canners, and how you prevent it. The thing is, botulism isn’t that scary if you understand how it works and why you must follow certain guidelines to ensure your home canned food is safe.

And so, I present the world’s first (as far as I know) Infographic about Botulism: How Not To Die From Botulism. Questions? Concerns? Favorite canning resources? Let’s share our knowledge in the comments. Happy Canning!

Click on the image or here for a full-size PDF of this infographic poster.


Note: Small edits have been made in response to reader feedback. Please reference back to this page, which will always link to the most recent version of the infographic. Thanks guys!


  1. Mara says

    Thank you for the great infographic! I’m going to try canning something for the first time this autumn, and have saved it to my harddrive, just in case.

  2. says

    I’ll admit that the one reason I’ve never tried pressure canning anything is because a) I was afraid the pressure canner would explode on me (which I’m told is much less probable now) and b) because I was terrified of poisoning my family. And the last two articles I’ve read in the mainstream media about canning haven’t helped (one case of botulism, one case of a woman’s fridge door being blown across the kitchen by improperly processed chutney). Just goes to show that even for “simple” things, i.e. things that our grandmothers and great grandmothers did, knowing the proper way to do something is of paramount importance.

  3. says

    I echo what Lynne said. Two seasons ago I picked up a pressure canner at the farmers market and I have been too daunted so far to use it. With power outages increasing in both frequency and duration, it might be wise to not depend entirely on the freezer. As always, thank you!

  4. Rob says

    Spotted a typo in the pie chart, Infant Botulism: “too acid to allos” should be “allows”. Very good work BTW.

      • Tanya says

        One more typo, because I bet this will get circulated nicely.

        Vegetables starting the 3rd paragraph under Acid Levels.

        And I’ve got to say–I feel like I’ve actually got a real (albeit beginner’s) understanding of this now. Fear is receding as knowledge edges it out. Thanks!

          • Laurel says

            Hi – Love your articles and this info graphic in particular but am having trouble with the tiny font size on an 8.5X11 print-out. I’d like to use it as a handout in our jam making classes (also love your no pectin jam guideline – have a laminated version next to my jam pot.) But back to the Big B info-graphic. Can you make a pdf version that will print double sided? or on two pages so the text size will be legible for those over 40? it looks like it will split nicely just before the punchline “so am I rolling the dice….”
            I tried adjusting the print settings in Adobe Reader without any luck.

          • Homebrew Husband says

            Laurel – you might be able to make this work from within Adobe Acrobat:
            (1) zoom/resize the Acrobat window to show the portion of the document you want.
            (2) Choose “Print…”
            (3) Under “Pages to Print” click on the arrow next to “More Options”
            (4) Choose “Current View”
            This will print the view you have set in your Acrobat window to print, and scale it to fit the paper size you have. You can then repeat this to get the other half of the document.

  5. says

    I had to send this to a few friends who are amazed I make my own jam since they are afraid they would give everyone they know botulism…I have to admit, it wasn’t anything I’ve ever thought of. Loved the Iron Man reference! :)

  6. Elizabeth Gibbeson says

    Thank you for this all important information. I have been showing my daughter how to can this year, both pressure canner and water bath, and have stressed cleanliness and following tested recipes. Then someone on the web or a friend tells her, “Oh, I never do that.” and I can only hope that she realizes they may be just lucky with their out-dated habits.

    BTW, thank you for your jam primer. I hadn’t made jam in many years and I was going nuts trying to find the basic no pectin jam formula to work with. The overly sugared ones just don’t taste “right” to me.

  7. says

    Thank you for sharing this! So many people are terrified of canning because the potential for botulism, and then there is the other half of the coin where you have people who don’t follow recipes for home canning at all, upping their chances for food borne illness. The ones that think putting hot liquid into the jar and flipping it upside down ensure proper canning. Or think that it’s ok to process meat in a water bath. This makes me cringe!
    As a home cook, I always love making a recipe my own by adding in my own ingredients or adaptations. However, when it comes to home canning, I follow those recipes exactly as called out. Ingredients, cook times, processing times. You can never be too careful.

  8. says

    What is the difference, then, between a pressure canner and a pressure cooker, and when will you have an infographic on canning meats and low-acid vegetables? No, not trying to add to your work pile, since I’m not canning a lot right now, but just interested. Thanks for your botulism infographic, which I zoomed up to 16% to read.

    • says

      Re: Difference between pressure canner and pressure cooker.

      Technically, there is not much difference. Ususally, pressure cookers are smaller and made of lighter materials. They often have a capacity that too low to be useful for canning and they may not hold pressure as effectively as higher quality canners.

      Pressure canners are large, thick-walled vessels that are slow to heat up, but also slow to cool down. Processing times have been calculated based on those heating and cooling times. To use a pressure cooker, you would have to recalculate processing times and perhaps heat the cooker more gradually. The goal is to get heat to the center of the contents in the jars without cooking everything beyond recognition in the process. Because cookers heat up quickly, but it still takes time for the contents of the jar to heat through, you can overcook the outer parts while still not reaching safe temperature at the inner parts. Cookers also cool down quickly, so if you use canner processing times, you may remove heat from the centers of the jars too soon.

      So, while there is technically little difference and one could certainly use a pressure cooker for canning with the right processing calculations, it is easier and safer to use a pressure canner, which requires no adjustments to the well known processing times.

    • Hal says

      To print a 3 page poster of the pdf with HP All-in-One printer try these settings:
      1. From the File drop-down menu select ‘Print’.
      2. In the pdf print dialogue box select printer ‘Properties’. *
      3. In the dialogue box that pops up select the ‘Features’ tab.
      4. Under Resizing Options, select ‘Borderless’ then ‘OK’.
      5. Back in the pdf print window under Page Sizing and Handling, select ‘Poster’–note the number of pages above the preview graphic and all the little grid squares in the graphic itself.
      6. In the ‘Tile Scale’ box enter ’15’. Don’t use the ‘Enter’ key unless you want the poster spread over 112 pages. Just click on one of the ‘Page Orientation’ buttons and the entry will update. You can leave the orientation in the ‘Landscape’ position without affecting the print.
      7. Select ‘Print’.
      *You may want to set your Print Quality to ‘Draft’ at this point to proof the settings before you make your final print, then come back later and choose the final quality you want. It will also give you a chance to see what kind of overlap you get with the default setting of ‘.005′.

      Hope this is helpful.
      Thanks, Hal (Melissa brought me)

    • Claire says

      I wondered the same thing: What’s the difference between a pressure canner and a pressure cooker? I thought you COULD use a pressure cooker for canning. Please, someone — comment!

      • Heather says

        See Bill’s response to this question, above. I’d also add that for pressure canning, you need to be able to reach and hold a specific minimum pressure (usually 11psi, but it depends on what you’re processing and whether you’re at a high elevation) to make sure the botulin spores are destroyed. Pressure cooking doesn’t require as exact a pressure, and often uses a lower pressure for cooking than is necessary for canning.

        SOME pressure cookers can double as pressure canners, but it depends on the exact one you have: its capacity and design. Contact the manufacturer to ask about your specific cooker, they’ll be able to answer that question.

        If you do decide to use a pressure cooker as a canner, MAKE SURE your pressure gauge is accurate, just as with a canner. Contact your state extension service for more about getting gauges tested.

  9. Melissa says

    Thank you so much for taking the time to make this! The infographic is awesome! I am a graduate student in Food Science and just wanted to mention for the folks that may have a pH meter, the industry standard for pH is closer to 4.2. That is so that if any chemical changes occur in the product over time that may cause small rises in pH, there is a little wiggle room to still keep the product safe.

  10. Jennifer says

    I really enjoyed your infographic! I’ve been canning now for about 5 years. I follow recipes from various tried and true cookbooks, and will continue to do so. But I am curious if there is a difference in canning using gas verses electric stove? I would think that a gas stove could get the pressure canner hotter than electric. I have a gas stove sitting in my garage with a giant burner that would be great for canning (or brewing beer!). I’m hoping to install it and find that canning gets that much easier!

    • says

      No, assuming enough heat is being applied, the pressure canner and the PSI determine the temp inside, not the type heat source. Think of it like this – a pot of boiling water at sea level will only ever get to 212 degrees F (boiling point). It doesn’t matter if gas, electric, propane or wood is heating the pot with the water in it. Pressure canner: same thing, except the sealed environment allows a higher temp to be achieved at the various PSI demarkations. 10# PSI is equal to 240 degrees, for example. I prefer gas because the very small incremental changes to keep the pressure canner at the right PSI are easier to achieve. I can on a large, 30,000 BTU gas burner (a lot like a turkey fryer type burner) and it’s been wonderful for pressure canning. I bet you’ll love your garage burner.

    • says

      We have all electric in our house, and we take our turkey-frier 50,000BTU propane burner out on the deck to can. It can get a canner full of water up to boiling in about 15 minutes – I gave up on timing the indoor electric burner after an hour. But, you *can* use electric, it just takes longer :)

      • Heather says

        If it takes way too long to bring the canner to a boil, try replacing your heating element. They do become inefficient over time. You can get replacements at any hardware store or home improvement store.

        • Benita says

          All pressure canners can be used as pressure cookers but not all pressure cookers can be used as pressure canners.

  11. Cynthia Friend says

    Your graphic is wonderful- I hope it gets widely distributed. But I’d like to suggest a small fix: the real name for the toxin that is produced is “botulin” not “botulism.”

  12. says

    It is also always worth noting that we’ve been canning a lot longer than we’ve had good knowledge of microbiology and that procedures became a lot more stringent over the 20th century. But, despite that relative ignorance, a very small number of people suffered from botulinum toxicity, even at the height of canning’s popularity.

    Lack of first-hand experience with home canning has made people vulnerable to scare stories. Meanwhile, we are poisoned by big agriculture with some regularity. (E. coli dosed greens, anyone?) Canning procedures are simple; anybody who can read and follow directions can achieve good (and safe) results.

    • says

      True. I had to finish this late late last night, but I wanted to do a section comparing deaths from e coli or salmonella to botulism. While botulism is just scary other food borne pathogens harm a lot more people every year. By a factor of 10,000 in some cases, as I recall.

  13. Brandy says

    Thank you for this information! I have never canned. I have taken a canning class, but have always been too afraid to actually can at home by myself. How does sugar play into the canning process? Is it just for taste or for safety? Is the sugar or the canning process preserving the fruit? Or is it a combination? What if the sugar was left out? Have you ever used honey or maple syrup? The response in the class was: “Follow the recipe.”

    • says

      Sugar (and salt) prevent the growth of bacteria due to osmotic pressure. When the concentration of sugars or salt in the food is greater than that within the bacteria, they lose water to the environment and either die or transform to spores. In very high sugar jams and jellies, botulism and other harmful bacteria can’t grow, which is why water bath canning remained a popular option for those products for so long. However, yeasts and fungi that consume the sugar and cause spoilage sometimes can grow in that high sugar environment if the cans aren’t sealed.

    • says

      To my understanding the sugar generally helps preserve the fruit in combination with pectin (use Pomona Pectin for a lower-sugar recipe- proportions are in the box)…. ONCE THE JAR IS OPEN. In my experience the low sugar jams mold more quickly in the fridge than the traditional high-sugar ones. IE sugar helps to slow decay of the fruit once the jar is opened or if it is not canned.
      The canning creates a clean vacuum- kills bacteria, removes oxygen- so that no decay can begin until the seal is broken.

    • says

      I believe canning classes that present info like that do a huge disservice to canners and add a lot more intimidation to the process than necessary. You can can safely high acid products without any additional sugar. The amount of sugar necessary to get a preserve hygroscopic (see Bill’s explanation above) and shelf stable without additional processing (BWB canning) is higher than even tested modern recipes call for. Sugar improves texture, helps maintain color, and of course makes preserves taste better, to a point. While there is an interplay between acid, processing time, sugar and/or salt concentrations in how safe a preserve is, it’s really maintaining that high acid level that is critical to prevent the growth of c. botulinum. I, personally, have no problem reducing the sugar content of high acid preserves or substituting part honey or maple syrup for the sweetening factor. However I always, always, always finish my preserves in a BWB. Note that if you use a pectin box recipe, the amount of sugar they call for is necessary to ensure a set with the pectin. I have a post on pectin-free jam making that goes into details about my method if you are interested. You can read it here.

      • Brandy says

        Thank you so much! Very good information. My kids and I are going to try our first batch of plum preserves this week. Since it is our first attempt, we are going to try your pectin free recipe. I am glad to have found your website.

  14. cptacek says

    I canned my first batch of zucchini/squash pickles this weekend. For 10 of them, I used the packet of Mrs. Wages pickle spice and followed the directions, which said to pack, pour the boiling white vinegar solution in the jars over the veges, lid, then boil for 5 minutes at 1000 ft altitude (5 1/2 minutes for me). The next 10 I used the Ball guide to home preserving, and it said pack, pour boiling apple cider vinegar/water solution (with spices) in the jars, lid, then boil for 15 minutes at 1000 ft altitude (I went for 20).

    Why the difference? That is a big difference in processing times.

    That reminds me…difference in altitude might make a good addition to your chart. Very informative, by the way.

    • says

      Well, the discouraging answer might be that the recipe on the Mrs. Wages isn’t following the same guidelines. But I’d guess that it has to do with the concentration of acid. If the Mrs. Wages called for 100% white vinegar, that’s very, very strong acidulation. A 50/50 mix (not sure what your ratio was) of apple cider vin and water would have half the acidulation of 100% vinegar, assuming all vinegars are standardized to 5% acidity, which is pretty typical. So you’ve got a different interaction of processing time and acid level.

  15. Nikki says


    Awesome infographic! I grew up eating only canned fruit/vegetables/jam. In fact, I think I have only ever purchased 1 or two jars of jam, thanks to the efforts of my awesome grandmothers who kept me in stock until I learned to make it myself. But one thing missing from your article (maybe one of your other commenters mentioned it, but I didn’t have time to read all of them) are warning signs of botulism or spoiling in general in home canned goods. Namely distended caps (ones that click up and down, but are still sealed), unsealed jars-except those that just didn’t seal in the bath, change in food color, or rusting of caps. These are the signs I was taught to watch for when I was a kid. If we found something with one of these signs we always treated it as suspect. Not that these things would necessarily have helped the gentleman in question, but personally if I had a jar that popped it’s seal after cooking I would have thrown it away.

    Just my two cents, thanks for another awesome post.


    • MQ says

      Many times a bulging lid occurs because the lid hasn’t tightly sealed and the contents have fermented–causing gas and swelling. But botulism doesn’t necessarily have to have a bulging jar lid to be present. In fact, it is odorless and tasteless and the food would probably look and taste fine and still be toxic if it were improperly canned. Proper canning time and temperature are the only ways to be safe. We’ve all heard the stories of the relatives who water-bathed their green beans for anywhere from half an hour or an hour and a half and ate them and lived to tell the tale–well, they also opened their jars and boiled the contents for 20-30 minutes. If there is toxin present, the boiling would denature it, but if any of the product is not in the boiling liquid for the required time, the toxin would still be present on that bean(or kernel of corn, slice of carrot, etc.). Now, the question is: which family member or friend do you want to give that toxic green bean to?

      • cptacek says

        I have been reading a site where the person adamantly stresses safe canning techniques, but as an added safety measure, encourages you to bring the food to a boiling temperature (i.e., she says frying with it, baking with it, etc, is ok) for at least 10 minutes after opening your pressure canned meats/veggies (anything not safe to WBC).

        Do you feel that is required? Also, can you explain what you mean by “boiling would denature it.” Are you saying in your comment that the toxins would be rendered safe after boiling, but that it is a huge roll of the dice if you feel the contents might be compromised, because there is no guarantee that every part of the pot of beans would get hot enough?

  16. Kobu says

    This is really important information for everyone to have and the explanation is easy to umderstand. Thank you. My posting is off the subject of home canning….but as long as we are talking about botulism….there is a 4th way to contract it (not represented on your chart) that is called iatrogenic botulism….which basically means that it can be contracted through its use as a medical treatment….and yes I am talking about Botox, Dysport and the other trade names out there. And no….I am not talking about counterfeit Botox but the real stuff. Many people don’t realize this but there are documented cases of individuals who have contracted the disease after injections, including deaths. Tens of thousands of reports made to the FDA of people suffering disabling symptoms after receiving injections. Didn’t mean to highjack this thread….but just wanted to point that out. And no….I am not someone who is against anyone who uses these products….but just happens to be someone (among many others) who has been battling illness for 3 years after receiving botulinum toxin injections (not being told of the real risks) and has spent countless hours studying the topic. Yes….thousands of others receive benefit without problems but there is an alarming number of people that have become severely affected. So again….thank you for educating people about botulism. I am just trying to do the same!

  17. says

    oh my goodness! Scary things broken down to easily understandable data! I figured I’d never be able to understand the chemistry in the process. Thank you for giving me more confidence in canning safety.

  18. says

    This is an awesome infographic. I have a lot of friends who want to learn to can to try some really strange recipes – like pickled eggs, that don’t *have* known-safe canning recipes. No matter how often I tell them to use a tested recipe, they still “throw the botulism dice”. And some that I’ve taught water bath canning to think they can use that technique for *any* canning (if they had the equipment to pressure can, I’d totally teach them how to use the pressure canner). Thanks for providing such useful information in an easy-to-learn format.

  19. MichelleB says

    Hi Erica! I so need advice. I followed the fermentation recipe you recommended from Wild Fermintation. I followed it to the letter but then noticed that other sites say to add vinegar to brines. His recipe doesn’t call for vinegar. I just want to make sure that his recipe is correct, without vinegar. Also, how long will fermented pickles last in the frig? We eat pickles very slowly. Can I take the fermented pickles (from his recipe) and after they are the flavor I want, heat the brine and raw can them? I don’t want to kill my family so pleeeeeeeaaaaase let me know. Thanks!!

    • Jennifer W says

      Michelle B,

      If you can the fermented pickles they will no longer be raw. If you are going to go to the trouble of fermenting, I would think that you would want to leave them raw. Most people ferment to eat the beneficial bacteria that is produced during fermentation.

      Depending upon your fermentation method, they should last 2 – 4 weeks. I do not use Wild Fermentation methods so I can’t guide you on how long the ferments should last. But, the book Wild Fermentation probably has guidelines that will answer your questions.

      If you want to can your pickles, you may want to use a vinegar solution and then water bath can the (using a verified recipe). Alternatively you can use a vinegar solution and leave the pickles in your fridge. They won’t last forever but they will last longer, possibly, then fermented. Some people use Apple Cider Vinegar for a possibly healthy solution when canning. You would need to verify with the ACV manufacturer the acidity for canning purposes.

  20. MQ says

    Check out the Master Food Preserver program offered by Cooperative Extension. I know it is offered in WA–I think it is in many other states also. I think they are usually in the county government listings. Wonderful program; informative and accurate. I’ve been appalled at the misinformation running amok on the web.

  21. Christena says

    I just made strawberry jam using strawberries, granulated sugar, lemon juice and homemade pectin (made by boiling down granny smith apples). Instead of canning, I just poured into jars and put in the freezer. Is this safe?

  22. says

    This is a fabulous infographic. That article was so frightening – it was alarming to hear about all his mistakes, and then the consequences he faced. I’m glad he survived, but it was also so helpful to hear what can happen if botulism attacks – it makes it such a more concrete risk, and an area I want to be even more vigilant (not that I wouldn’t have been already!)

  23. laura says

    UUgh…Tried to tell my MIL that she shouldn’t can (pressure or otherwise) pumpkin puree because of the risk of botulism. She, of course, ignored me (as she does with EVERYTHING.)

    Honestly, waiting for the day she gets herself and other family members ill, so I can pull the “I told you so” card.

  24. AZSahuaro says

    Thanks for this. I intended to show it to my friends who I can with because they never read the recipes, and think it’s totally fine to add random ingredients to tomato sauce. They make me feel like such a jerk when I tell them why it’s important to follow the recipe. Most recently, they added liquid smoke to our tomato sauce that we canned – do you think that has any impact?

  25. says

    Thanks for the great chart! A retired Chef, I teach Serv-Safe and you’ve created a wonderful user friendly graphic. I posted the link to the Hampton Grows FB page as well. Just started visiting your page… loving what I’ve read so far!

  26. Peahen says

    Hello have so enjoyed this website since recently coming across it. Thank you for all the good thought and work and fun you’ve put into it.

    I’m terrified I’ve given bad jam to people and am going to recall it; I wish I’d read a little more carefully before beginning. Even still, it wasn’t until after I’d shared it that I realized a couple of things I’m afraid I did wrong. I’ll still ask for them to dump it out, but am curious how far off the proper path I actually veered, so I can do better (and maybe someone else did the same thing, or can be warned off my errant path of preserves).

    I started with a blueberry-shallot-rosemary recipe. I used raspberries and a wee bit of basil from our yard, plus the small (1-2 tablespoons, chopped) shallot. The recipe called for a tablespoon of balsamic vinegar, so I added that. I cooked it a good while as it reduced down, then put it in new, dishwasher-sterilized (and kept warm) jars. They’re the very small, faceted kind. I don’t have the special pot for boiling the filled jars, so set several of the screw-on ring tops at the bottom of the pot. The water was boiling when I set all the jars in. I left them in for 20 minutes probably, because I never saw the full boil again.

    When I took them out, they did make the popping noise, and, when I checked a day later they made the proper sound when tapped, and are quite well sealed. But I’m concerned about having veered from the recipe (not from a special “approved” book, just a nice lady on the Internet), and that they did not reach the correct temperature. I read a day or two later that I should maybe have kept the lid on the pot.

    My husband has eaten a whole jar and not died. Seems like, overall, statistics are on our side, but I don’t just want to be lucky, I want to do it right and make awesome jam and figure it out well enough to be creative without wiping out my loved ones.

    Apologies for the long post. I appreciate any insights anyone can provide.

    • Hazel says

      With a cup of sugar to 4 cups of fruit (I think I found your recipe :-) ) I’d say mould or fermenting would be the biggest long term risks, though 20 minutes in boiling water may have put paid to even that; but I’m British and we don’t water bath jam at all.

      Personally, I would tell them just to eat it sooner rather than later, but if you’re concerned please do as you feel fit. I appreciate my advice is not USDA approved!
      (I do follow canning instructions very carefully when bottling/canning ‘straight foods’, but am comfortable with British traditions when making jams, jellies, pickles and chutneys. I am not advocating people follow my methods, just giving my experience.)

      • Peahen says

        Thank you, Hazel. I appreciate your posting a reply! Fermenting doesn’t sound all bad unless it goes on our toddler’s sandwiches. :)

        I’ve got berries macerating in the fridge now. I’m hoping a taller pot and a lid on during the water bath (ow, hot bath!) will calm my nerves for the next round.

        The note about “traditions” strikes nicely with me because this whole berry picking, jam making business has really had me thinking about family and how my very wide range of relatives and ancestors have picked, processed and preserved food over time. It was, in a way, the inspiration for my giving it a try at all. I did have a near-time ancestor die of botulism from a fermented indigenous food – a far cry from my dinky jar of obsession – but it did make the concerns even more real.

        That said, apparently my husband did put some of the jam on our kid’s sandwich this morning, to no ill effect. Seems I failed to mention the little stew I was in over it. Ahem.

        Alright. Thanks again!

        • Hazel says

          You’re welcome!
          I can understand your worries given your family history. Again, please do what you feel comfortable with.

          I am braced for the backlash though- I nearly didn’t comment because I usually get a torrent of accusations of irresponsibility.
          The fact is that the UK on the whole doesn’t water bath any pickles, chutneys, jellies or jams (though these usually contain equal amounts of sugar to fruit for long term storage). The acid and/or sugar levels in these make the growth of any nasty bacterium very unlikely. There have been 6 cases of food borne botulism in the UK since 1989 (when 26 people got it from commercial yoghurt!), all from homemade foods from other countries.
          Other forms of canning are different and I am in no way undermining Erica’s advice.

          That should cover every thing! (Thank you for an interesting and informative post Erica.)

  27. Serina says

    I have been using the blue chair jam book for inspiration/ to drool on, and she uses an oven technique for processing the jars. Do you think this is a safe way to preserve other things that are high acid or high sugar? Curious for your thoughts.

    • says

      The official policy is this:
      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.

      My thoughts:
      There is a big difference between the heat transfer of air and water. Just think about how you can stick your hand into a 500 degree oven to pull something out without consequence, but if you stuck your hand into a 212 degree pot of boiling water you’d suffer immediate massive burns. For this reason, the processing times of food in an oven would be far, far different than in a boiling water bath, and there is really no way to know what those times are.

      The problem with under-processing a high acid food, from a botulism standpoint, is that there are certain molds which can, if they take hold in your preserve, actually change the pH so that your formerly safe high acid preserve becomes low acid. Low acid means risk of botulism spores germinating, and we are back to a potentially dangerous product. The chance of this happening in a high sugar, high acid preserve is very remote, but more likely in the lower-sugar jams I tend to make. Processing in a bwb canner for the full time recommended in a tested recipe insures that mold spores and other bacteria that might be in the jar before processing are destroyed.

      • Serina says

        That makes sense, if I have recently used that technique on some low sugar jam should I toss it or can I BWB it (or freeze it) and call it good?

  28. Happy says

    I’m interested in the answer to Serina’s question also, since I have been sterilising jars in the oven at 130C for 15 mins plus for jam.
    I also would like clarification if one needs to do BOTH heat and acidification or if heat alone is enough?

    I have used a recipe for slow roasting garlic fully immersed in olive oil in the oven for 1 1/2 hours at 130C, then oil and garlic (garlic always covered) placed into jar sterilised in the above fashion, then refrigerated and kept for up to 6 weeks. I’ve had no issues the couple of times I’ve done this, but the botulism police visited recently and put the wind up me.Do I need to get some vinegar into the act somehow as well?

    Love your work Erica, (the botulism police are probably friends of the retirement police.)

    • says

      Hi Happy,
      See above for my thoughts on the oven-processing of jams. I am skeptical that 130 degrees (265 for U.S. readers) for 15 minutes or so would be sufficient to assure reliable heat transfer.

      In a pressure cooker, heat alone is used to bring temperatures up to safe levels. U.S. guidelines are very clear that raw garlic in olive oil stored at room temperature is a potential (likely) botulism vector.

      What you describe, an extended cook of the garlic at 130 degrees (a temperature oil can reach, unlike water) followed by prompt and constant refrigeration seems quite safe to me. In this case, I am simply speculating about the advantages of the garlic cook, and what keeps your product “officially” safe is the refrigeration, so don’t skip this step. Many products that would be a botulism risk at room temperature (plastic tubs of pico de gallo come to mind) are perfectly safe if stored consistently under refrigeration. I think the botulism police give you a pass on this one.

      • Newbie Girl says

        Hello Erica,
        So, I’m afraid I may have done something wrong, but I have been canning some things with my mum and the way she always did canning, was to boil all her ingredients for quite a while – longer than 90 minutes, even – ie: jams, and a red pepper/fresh romano bean/oil and tomato preserve that we all love…she also adds salt, then, after cooking for a while, she puts it all in canning jars that she has rinsed with super hot water out of the tap, then, she puts the cooked stuff in the jars, seals them, and quickly moves them to a spot she has prepared in a closet or enclosed space, full of blankets – and she puts all the jars together so they keep eachother hot for a long time, covers them all with at least 3 or 4 more layers of fabric/blankets and leaves them there for days until they cool.

        Does this sound ok? She is European and this is how they did things back home always….

        Anyhow, my last question is: I did the same method with some tomatoes from our garden, some veggies I had lying around, chopped fine, some olive oil, lots of dried basil and salt and fresh garlic and made a pasta sauce, put it in jars and under blankets. SO, would the tomatoes be acidic enough to make this safe or should I have boiled the jars for 15 minutes after I filled them with the sauce? Is it too late to do it now, it has been about a week or two since I made the sauce and I don’t want to lose it all!

        Thank you so much!

        • Benita says

          Hi Newbie Girl,
          The method you describe in no way meets the current research-based recommendations for safe home canning. You are rolling the dice (or playing Russian roulette with a loaded gun, etc, etc) with your family’s health. DO NOT use your product, dump it down the garbage disposal. At your next canning session please refer to resources such as
          the National Center for Home Food Preservation –
          Ball Blue Book or Ball Complete Book of Home Preserving, or
          So Easy to Preserve -
          You owe it to your family to can safely.

          • Newbie Girl says

            Hi Benita,
            Sorry about the delay, and *Thank you* for your reply!!! – you would be horrified to know how much resistance and %$#@$ I got from my old school dad for suggesting that my mum’s ways were unhealthy/unsafe, but I really appreciate all your input and validation. My mum actually took all of them out of the jars, recooked them, recanned them, and then cooked them again for a good half hour.
            So, I have to convince them to chuck it all still…..

  29. says

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  30. Florence says

    Thank you for confirming I’m canning properly! I didn’t years ago..but thanks to reading Canning Books, I cleaned up my act! I have a pressure cooker and water bath canner. I love your makes perfect sense. Thank you for providing great and safe information available to all of us ‘Canners’! Very appreciated!

  31. Cap'n Jan says

    Very nice chart! The sporulation of C. Botulinum is particularly important to understand and this does a good and clever job. I have had people tell me that ‘soil is not what it used to be’, which is why we have to pressure can now when we could water bath can in the ‘good old days’. That of course, is nonsense, C.B. has been around forEVAAAR. People probably did die of botulism in the good old days, but it was probably still quite rare – everybody knew to NOT EAT FOOD FROM JARS WITH A FAILED SEAL!! Usually jars sat on the shelf for long enough to show signs of spoilage before being consumed, as the family was still eating last year’s green beans. If the jar shows spoilage, or if there isn’t that wonderful ‘thuck’ sound indicating a vacuum when you open the jar, toss it!

    Bringing me to a question I hope you will be kind enough to answer!

    Can you please help me find the reference that says C. Botulinum can remain in a spore state for thousands of years? I have heard ‘many years’, read ‘many years’, even on the sites you would expect to know something about science they say ‘many years’. I am not doubting you, spores are remarkable, and I could see it happening. Just curious if you have an article with some data (fossil records, for example).

    It is a major annoyance of mine when I hear that ‘canning pureed soups’ (for example) is unsafe. It is not necessarily unsafe, but it COULD be unsafe as it has not been tested in a lab with all the variations possible. Pureeing foods introduces a variable amount of air depending on the puree method and the amount of time in the blender. Air in the jars will impede heat transfer (air is an insulator, that is why you insure there are no air pockets), ergo there could be a problem with SOME pureed soups, but not others. I’ll stick with not pureeing ;-> But I was glad to finally talk with someone who knew the science behind the warning. I was the kid that always asked ‘WHY!!!?” My poor Mumma!

    Thanks! (Sorry this is such a ramble!!)

    I am cruising the site and having fun with it!

    • says

      “Bacterial endospores are dormant microbial structures that are highly resistant to chemical, physical, and radiation sterilization processes (20, 31). They represent one of the most successful survival strategies of microorganisms and are formed when members of spore-forming genera (e.g., Bacillus and Clostridium) face unfavorable conditions, such as environmental extremes or starvation (19, 34). Once they are formed, endospores can stay dormant for extended periods of time, from thousands (8, 13, 20, 25, 33) to millions (3, 35) of years, although for the more extreme claims of longevity it is difficult to rule out modern contamination (37).”
      Emphasis mine. From the American Society for Microbiology:

      • Cap'n Jan says

        Thank you Erica! That was a fascinating article. Although they do not that, as you said, it is difficult to rule out modern contamination. However ‘amber specimens’ are somewhat proof positive that the spores can remain viable if the correct environmental conditions exist (perfect oxygen isolation, etc.)

        So, I am educated!

        Here’s something else interesting. I have a pet peeve when I see things like ‘Pureed soups are not safe’, with no explanation as to WHY they are ‘not safe’. I’ve always hated ‘doctors’ that pat you on the head and tell you ‘Look little lady, we’ll take care of EVERYTHING’. I want to know, even if I won’t like the answer. But I digress, back to pureed soups: My guess is that they may indeed be safe under certain conditions. HOWEVER, this is the catch: Pureeing by the very nature of the act, incorporates air into the mixture. Air is the fly in the ointment, it can be difficult to raise the temperature in a jar, even given that convection is the method of heat transfer in mobile fluids. The air is ‘trapped’ between very small particles. Ergo, there is no guarantee that my pureed soup is the same as yours, thus it would be impossible to give ‘guidelines’ that would work in both cases. Ergo it is ‘unsafe’. If you know differently from this, please help me understand. (I’m an engineer, albeit retired, I like numbers and absolute facts! If you are of the same bent, here is some fun reading although it is in reference to commercial canning: (I don’t own it as it is a bit rich for my blood, but found excerpts using Google – hope this won’t get lost, don’t know if you have THIS much of an interest!!

        I won’t can pureed soups because I do not have the equipment to insure its safety, although I would love to. I love my pepper soup and want it in jars, ready to serve! But I’ll have to go with the simpler, ‘prepare the peppers and the broth’ fill the jars, can them and puree after the fact. Still, saves a lot of work and prep time!

        Fair Winds, Erica and thank you for the site, intriguing! I am always willing to learn new things and I’ve learned a few perusing your archives!

        Cap’n Jan

  32. Barb Krohn says

    I purchased and canned 6 cases of peaches this past week! I canned 35 quarts and 32 pints. A day later a Listeria outbreak made the news and all my cases made the recall list! I did research online and talked to our local Extension Office, who referred me to the U of M. They did some research and told they could not be 100% sure the heat in the canning process killed the Listeria. I pressure canned at 6lbs for 10 min per my pressure canning cookbook. I’ve canned for over 40 years (everything) and this is the first time I feel the peaches should be dumped! I’d appreciate your take on heat killing Listeria. Thank you!

  33. says

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  34. Jane B says

    Before you partake: How did your host can those beans?

    My family went to dinner at a new friend’s house. Afterwards the lady and I shared cooking canning techniques. Her “hot tip” was that the green beans that she had served at dinner turned out just great without having to do the “pressure cooker thing”. As I listened (with considerable consternation) she explained that they turned out “just fine” using a hot water bath. FORTUNATELY we did not die of botulism. UN-fortunately she was totally UN-phased by my explanation of the dangers. We will never go to her house again.

    I really wish I had had your excellent infographic at the time. It might have commanded her attention.

    MORAL OF THE STORY: It might be wise to inquire about the techniques used to prepare the home canned foods BEFORE you eat them.

  35. says

    Hey Erica,

    I love the infographic! It amazes me how many requests I still get for canning low acid foods in water with a water bath canner! I can only hope that they didn’t find an unreliable website guiding them on how!

    Thanks for sharing your information. You clearly have researched botulism a ton, and I thank you for sharing that information rather than keeping it to yourself. I now feel more confident than ever on not dying from botulism, LOL!

    All the best,

  36. Daniel says

    Hi Erica,
    I just canned tomatoes for the first time, adding 2 tbsp of lemon juice to each quart sized jar as indicated in the recipe. I was really set on following the instructions super carefully, but my friend who was helping me can somehow convinced me to put a few leaves of basil at the bottom of each jar for flavour. Does this make the jars unsafe? I imagine the environment is still acidic enough and wouldn’t be affected by such a small amount of basil. But better safe than sorry!

  37. Abigail says

    Hi! I have been experimenting with no sugar no pectin jams and am not picky about texture and okay with a more syrupy result. I only use high acid ingredients, berries etc. Is this safe? Oregon extension is telling me no, but I don’t really see why when they have canned fruit that don’t include sugar or pectin, why is what I am doing unsafe?
    I also canned blueberry applesauce and they are telling me since there are not tested recipes I should freeze, which I am not interested in doing. What do you think?
    Here is what they said to me:
    Good Morning.

    Thank you for contacting us. It’s true … there are lots of great approved recipes to use for making jams and jellies. The proportions in these recipes should be followed to ensure both a safe and quality product.

    Bacteria need moisture to grow. The sugar added to jellied products binds with the water/moisture in the product – essentially taking away the moisture so bacteria cannot grow. Low/No sugar jams have some calcium in them, which binds to the water/moisture (in place of sugar) – again making it drier and less likely for bacteria to grow. If you would like to experiment with sugar amounts you are welcome to freeze or refrigerate the product. If you wish to can the product, it is recommended to follow tested recipes.

    The combination of apples and blueberries sounds delicious! Since we don’t know the correct processing time for the consistency and acidity level, it is best to freeze or refrigerate this product instead. Perhaps you could also can the applesauce and blueberries separately – following each of the tested recipes – and then mix them together when opening the jar.

    We do not recommend using a pH meter for home canning.

    Best wishes,


  1. […] Botulism poisoning is definitely rare – in 2011, 145 cases were reported and only 15% of those were foodborne (so about 22 cases total). You are three times more likely to die by lightning. But nonetheless, botulism poisoning is a risk you take when you decide to not follow trusty recipes or experiment with ingredients (particularly low acid ones) or processing methods. (For more reading on this topic, I encourage you to check out NW Edible’s most excellent post & infographic entitled: How to Not Die from Botulism.) […]

  2. […] How to Not Die From Botulism: What Home Canners Need to Know About the World’s Most Deadly Tox… START HERE. Best write up. Ever. And there is an awesome infograph about it! With Iron Man metaphors! Seriously, can’t recommend this one enough, especially for nervous new-folk. […]

  3. […] How Not To Die From Botulism: What Home Canners Need To Know About The World’s Most Deadly Tox…. It explains so much about botulism, and in a simple fun way. Make sure to click on the news link about the guy who contracted botulism from his home-canned elk meat, and make sure to note his process. Not a canning role model, and surely a CDC statistic for the year. […]

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