A couple of weeks ago, I dropped a sprig of fresh, aromatic organic rosemary in a pretty bottle and filled it with olive oil. What I didn’t know then is that I might have killed us with that oil.
It turns out, herb-infused oil is one of the twelve foods, or more precisely, food groups, that can cause botulism, a rare, but life-threatening food-borne illness that causes paralysis and may take weeks, even months to recover.
If you read me regularly, you’ll know I included an herbed oil in a post, 5 Ways to use fresh rosemary. A few hours after I published that post, an alert blogger friend notified me of the danger. I retracted the tip immediately.
To reach as many people as possible, I also published–and publicized as best I know how–a new article, clearly warning of the risk, along with a link to the University of Maine Cooperative Extension office article, Safe Homemade Flavored and Infused Oils.
How did this happen?
How could I, a grandmother who has known about botulism since my teens, not know that fresh herbs carry the bacteria, Clostridium botulinum, which causes botulism, or that putting them in oil would provide exactly the environment the bacteria needs to grow?
Fresh rosemary
It never occurred to me such a thing could be harmful. In how many gourmet gift shops have I seen such bottles filled with oil and herbs? Turns out, commercial purveyors add a special acid-rich ingredient to their herbed oils, in a process not easily duplicated at home.
But also, the Center for Disease Control and Prevention (CDC), in “Botulism prevention: Many cases of botulism are preventable“, tells us that new sources of botulism poisoning are found nearly every decade. Given I’m more than five decades away from my last Home Ec class, where we learned about what causes botulism, I may have some catching up to do.
What else might I have missed in the last 50-some years?
My experience set me to wondering. What other foods carrying the bacteria escaped my ken? How we can protect ourselves when cleaning, preparing, eating and storing those foods? I did some digging.
Baked potatoes in foil (A morgueFile Free photo)
In my research, I found twelve foods and/or food groups that can put us and our families at risk for botulism. Most I already knew about. But baked potatoes wrapped in foil? That one’s new too. Thankfully, we’ve never baked our potatoes in foil.
Is this a comprehensive list? Don’t count on it. I’ve done my best to ferret out the foods that may put us at risk. The twelve foods in the joint lists you’ll find on this page come from no less authoritative sites than the websites of the CDC and the United States Food and Drug Administration (FDA).
Before I share the lists, you may be wondering what botulism is and what causes it. Here are the facts as I understand them.
What is botulism?
Botulism is a deadly food-borne disease caused by the bacterium C. botulinum. This rod-like bacteria lives in the soil and can be found in many plants and animals.
Clostridium botulinum – Public domain image courtesy the CDC and Wikipedia user Kookaburra
When active, it produces a neurotoxin that attacks the nerves in our muscles, including the ones that help us breathe.
Only a small amount–we’re talking nano grams–can immobilize and kill a person. Because the symptoms are similar to other diseases, such as Guillain-Barré Syndrome, doctors find it difficult to detect. Diagnosis takes a week or more.
Thankfully, an anti-toxin is available to help treat the illness, and in most cases, prevent death. Recovery, however, may take weeks or months.
Other ways we can get botulism
While this article concerns itself with food-borne botulism, you should know that it can invade our bodies through other means, such as wounds and, possibly, according to the FDA, (pdf, p. 109), through invasive digestive-track surgeries.
In addition to these, MedScape, which lists six forms of botulism, includes inhalational botulism and adult intestinal colonization botulism.
Infants can get it from eating dirt, as well as from certain foods that are not dangers to children over one year old or to adults. Those foods are on the list, in their own section.
Fortunately for humans, C. botulinum needs a near-oxygen-free environment to grow, and doesn’t like acid. Air and acids such as vinegar, lemon and lime juice help to keep us safe from food-borne botulism.
That’s one reason people preserve foods by pickling them in vinegar.
Three botulism facts to keep in mind
While it is deadly, C. botulinum needs a specific environment to grow. We can lessen our chances of getting this disease if we remember these three facts.
Home-canned Brussels sprouts need special handling to prevent botulism – A morgueFile Free photo
- C. botulinum may be carried on almost any food that has little or no acid. Green beans, Brussels sprouts, carrots and cabbage, like most vegetables and many fruits, contain very little acid. Other examples (not a complete list) of low-acid foods include mushrooms, meats, fish and eggs. C. botulinum spores may piggy-back on any such foods.
- C. botulinum needs a low-oxygen, low-acid environment.When we place low-acid or non-acidic foods in a low-oxygen environment, such as a home-canning jar, we give them the perfect environment to go forth and multiply. Similarly, covering low-acid foods in oil reduces or eliminates oxygen availability and provides a botulinum-loving environment. That’s why my herbed oil could have become a deadly, if tasty, food.
- C. botulinum outbreaks in the U.S. occur most often due to improper home-canning. If you plan to can food at home, or to eat home-canned food, follow the guidelines outlined in the CDC’s article titled Home Canned Foods: Protect yourself from botulism.
Now, on to that food list. There are two, actually–one for infants, and another for everyone else.
Which foods most likely carry botulism?
Reports from the FDA, as well as the CDC, name twelve foods, or food groups that may carry C. Botulinum to humans. They break it up into three foods for infants under one year, and nine that may pose a risk to all the rest of us.
Botulism-contaminated jalapeno peppers – Public domain image, courtesy the CDC and Dr. Chas. Hatheway, ID #3884
While I don’t find this statement in the second edition, in the first edition of its Bad Bug Book, the FDA said,
Most of the 10 to 30 [botulism] outbreaks that are reported annually in the United States are associated with inadequately processed, home-canned foods, but occasionally commercially produced foods have been involved in outbreaks. [Emphasis mine.] Sausages, meat products, canned vegetables and seafood products have been the most frequent vehicles for human botulism.
On its FoodSafety.gov website, the United States Department of Health and Human Services (DHHS), under which both the CDC and FDA run, identifies the first eleven of these twelve at-risk foods this way. I ran across the twelfth group on a separate FDA page.
Infants
Jar of honey – A morgueFile Free photo
Infants one year of age and under must never eat the following foods.
- Honey
- Home-canned vegetables and fruits
- Corn syrup
Note that infant botulism is classified separately, not as a food-borne illness. The Minnesota Department of Health explains it this way: An infant can get botulism
When a baby eats or drinks something that contains spores of the bacteria – the hard-shelled form that the bacteria take on when they aren’t able to grow and reproduce.
Because honey, home-canned vegetables and fruits, and corn syrup may contain the spores, even if they’re not actively reproducing, these foods, as well as soil and even dirt in the carpet, may cause infant botulism.
Sometimes you have to wonder how we ever managed to over-populate Mother Earth, don’t you? Not that we should look at these dangers flippantly. Not at all! But to remind ourselves, lest we think we have to put our babies in bubble suits, that this disease is relatively rare.
Children and adults
For children one year and older, and for adults, the DHHS identifies the following high-risk foods.
- Home-canned foods with a low acid content
- Improperly canned commercial foods
- Home-canned or fermented fish
- Herb-infused oils
- Baked potatoes in aluminum foil
- Cheese sauce
- Bottled garlic
- Foods held warm for extended periods of time
- Frozen, fully cooked products (Not on the DHHS list, but found in a separate article published by the FDA).*
*The FDA , in its article titled Frozen, Fully-Cooked Products & Botulism – Food Safety Advisory, explains why they’ve issued this caution and what we need to do to protect ourselves.
Assorted vegetables and fruits from our latest farm box
How do we protect ourselves?
The DHHS offers this somewhat cryptic prevention advice.
- Be very careful when canning foods at home
- Do not let babies eat honey
- Get prompt medical care for infected wounds
The CDC gives a longer version with plenty of specific information to help you protect your family. Please go to the their web site and read everything they’ve published about botulism. We don’t want to take any more risks than we have to!
You can also find information on safe home canning methods through your local county extension office. Some offer classes. They may also offer free, easy-to-follow, how-to printed instruction guides. You can find them through this interactive map on the Gardening KnowHow site. Sure, it’s a gardening site. The extension offices help gardeners as well as home food preservationists.
What to do if you think you may have botulism-infected food
Wear plastic gloves when handling suspect food
About half a century ago, in an ancient Home Ec class, I learned that the first rule of thumb in food safety is always, When in doubt, throw it out. According to the CDC, that’s still sound advice, but with this bug, it’s more complicated than that. We can’t just chuck it down the drain or into the dumpster. C. Botulinum is a bio toxin. Handle suspect foods with plastic gloves and a lot of care.
How to tell when to doubt? Check out the CDC guide for that. Please read the complete guide, especially this section: Safely dispose of food and cans that may be contaminated.
Stay safe–Do some research
That’s what I’ve learned about botulism so far. Thankfully, botulism poisoning is rare. I’ll return and post updates as I learn more. I hope the links on this page help you to make healthy decisions about preserving the foods you love and help to keep you and your loved ones safe
Please don’t assume I’ve covered every food and every possibility. Follow the links. Do the research. Ask questions of the folks at your local county extension office. (To find yours, see link in item #2 under “Breaking it Down.”)
If you have a question about a specific food and don’t find it in any of the links referred to on this page, write, call or send an e-mail to the Centers for Disease Control. Here is the contact information they provide on the page I linked to earlier in the article.
Address: 1600 Clifton Road Atlanta, GA 30329-4027 USA
Telephone: 800-CDC-INFO (800-232-4636), TTY: 888-232-6348
Email CDC-INFO
Do what you can to keep yourself and your loved ones safe from this deadly disease.
♥ ♥ ♥
Shared on Love healthy recipes? Welcome to the the healthy living link party #106.
Updated:
10/5/17, repaired broken links–again–and because the government web sites change with some frequency, I removed the tips for preventing botulism and referred readers directly to the DHHS and CDC for the most up-to-date information.
4/1/17, added CDC contact info
7/17/16, repaired broken links
YayYay's Kitchen 
Hello! Thank you so much for the informative article! I stumbled onto this on accident and at the weirdest time. I noticed the rosemary plant in your photo are quickly got worried. Is there a way that you could get botulism from making your own rosemary water (by boiling on the stove) to apply topically or is it mainly oil that’s the problem?
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Thank you for visiting my kitchen! In answer to your question, please refer to the boxed text at the top of the article. I am not an expert. For such questions please contact your local county extension agent or a poison control center.
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That’s a good idea! Thank you for taking the time to reply! 🙂
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Hello!! love the infomation, can botulism grow in chimichurri? It’s a mix of fresh parsley and garlic with a few vinegar and vegetable oil. And also can it grow if I keep that mix in the fridge? Or what do you recommend?
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Thank you, Ana. I do not know. I’m not an expert, just a granny trying to keep herself informed and share what she has learned. The article includes several links to government articles on botulism. I also suggest you contact your local County Extension Office wherever you live in the US, as they usually have a food safety person available to help local residents with food preservation and safety questions. At least they used to when I was young. I hope that hasn’t changed!
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If you simple dry the rosemary first, botulism cannot grow in the oil. But the rosemary must be bone dry.
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Thank you for your note, Amy. The USDA Cooperative Extension program agrees with you, as long as we heat the oil. In the first section of this post, you’ll find a link to the Maine Cooperative Extension Office bulletin on preparing flavored and infused oils at home. I’ll quote the relative section in full here.
“1. Best Home Method: Flavored or Infused Oils from Dried Spices
“Using dried garlic and/or herbs is the safest way to make infused oils without acidifying the product. Fresh herbs introduce water into the oil, and dangerous bacteria need water to grow. Dried herbs and garlic add no water to the oil, so bacteria can’t grow.
“Select a good-quality olive or other vegetable oil. Add your flavor additives to a clean container. Heat the oil to 180°F in a pot. Pour the oil over the dried additives, cap your container, and cool.”
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I just opened a jar of Grey Poupon Course Ground mustard and the fully-sealed lid seemed to pop open with a clump of mustard stuck to the lid as if the jar had been over-filled. I’m a little nervous about using it. What say you?
Your article is very informative. Thank you.
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Thank you. I’m no expert on food safety. You might consider calling the Grey Poupon company and inquiring about that clump. Alternatively, your local County Extension agent might be willing to take a look and advise you. Or you could heed the advice of my upright, severely coiffured Home Ec teacher back in the 1960s, who admonished us again and again and even put the question on the final exam: When in doubt, throw it out.
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Thank you for all this info.
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You’re welcome!
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I just opened a jar of Padrone peppers I pickled 6 weeks ago. There was juice on the shelf when I moved them so I washed the jar and set it on the counter to dry. A couple hours later I noticed more juice on the counter so I opened the jar. When the lid popped the peppers came up and the pickling solution spread all over the counter. The jar continued to bubble. The peppers were not processed in the pressure canner, just pickled. They smell fine, no foul odors. What do you think happened? I’ve pickled peppers this way for years with no problems.
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Having never pickled peppers, or much of anything for that matter, I have no idea what happened, @hoi polloi boy. Whenever I question any food in my fridge, freezer or pantry, I adhere to that old standby: When in doubt, throw it out. If you want to explore what might have happened to your home canned food and live in the United States, I suggest you contact your local County Extension Agent and see what advice they might give you about your experience with your pickles.
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Question: a friend just told me that tomatoes with ruptured skin-like from too much rain-will grow botulism. Is this true?
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That’s not one I’ve seen so far in any of the FDA or CDC literature, Alice, but the CDC does state on its page titled “Botulism prevention: Many cases of botulism are preventable,” (linked in my article above), that “new sources of food borne botulism continue to be identified.” I suggest bookmarking that page, as they do update it from time to time, as well as taking advantage of the phone numbers and email address, which the CDC kindly provides and invites us all to use should we have more questions.
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You state that botulism can be killed by boiling jars for ten minutes. This is incorrect. Low acid foods need to be processed in a proper pressure canner which actually gets hotter than boiling. This heat needs to then be maintained for at last twenty minutes depending on the size of jar.
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Thank you for your comment and welcome to my kitchen, Nancy. As I noted in that section, my information came directly from the Center for Disease Control’s recommendations for handling Home-canned foods, to which I linked. Perhaps my language was ambiguous? I am responding via mobile phone now, but will take a look later tonight and clarify as best I can. I encourage you to follow the link for CDC guidance. They are the experts.
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Nancy, thank you again for your helpful comment. I’ve updated that third point in what I hope forestalls any further ambiguity.
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I pickle garlic in dark vinegar but garlic is notorious for botulism if using just oil only. Re-heating frozen food is another food to be wary of. The U.S. Government has lots of free publications with information regarding food safety for canning, pickling and freezing food. These are great, and it is for the most part free or they used to be. Quite extensive with many recipes. I didn’t know about the potato and foil though. I used to bake them in foil but ate them right away. Wow. Thanks.
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Thank you Stephan. Yes, the US Government publications on food safety are extremely useful for the home cook.
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When I was a child my mother, unknowingly made grape juice in a silver pitcher. I drank the grape juice and it made me very sick. I was quite young and don’t remember the incident. For years I didn’t like grape juice and didn’t know why. My mom later told me she thought I was going to die after I drank the juice from the silver pitcher. It gave her quite a scare. I’m now 56 years old and I still don’t like anything grape flavored… Probably from the incident, I’m thinking. “o)
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My goodness, I can imagine how terrifying that must have been for your mother–and for little you. Isn’t it interesting how our bodies remember a trauma like that, while our minds have no conscious memory of it?
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Oops!
“Fortunately for humans, C. botulinum needs oxygen to grow”
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Oops is right! Thank you so much for taking the time to mention it. Fixed.
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Please…on the contrary…C. Botulinum is anaerobic: it needs oxygen free environments! Like the oil.
https://en.m.wikipedia.org/wiki/Clostridium_botulinum
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Yes, indeed—as the article states repeatedly. If you see language that indicates otherwise, I’d appreciate your pointing it out. Going back through the article, I’m not finding an instance of the error you mention, and I’d surely like to fix it if I’m missing it.
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I purchased about six smaller bottles of olive oil at a local Home and Garden Show…some of them are still unopened. I noticed the other day that a couple of them are now flocked with an unusual growth….that lead me to some research, and I think I should contact the original vendor and see what he thinks. This stuff wasn’t cheap, either…my mother consumed some of it, on bread at her ninetieth birthday party; is it possible the bread crumbs contaminated the olive oil remaining in the bottle ? no unusual symptoms…but now, as I do some research, I don’t think I’d even wanna let the local wildlife lick it up…
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Goodness Christopher. I hope your mom is okay.
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Hi. Thank you for your informative article. I am always looking for up-dated information since I am a” home canner” myself. I am looking for information on infused honey if you have any knowledge of this. I am wondering if there is a shelf life for home-made herb or alcohol infused honey. I stumbled across your blog looking for this information on-line.
Keep up the good work!
Maria
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After this experience, I’m wary of herb infusions. I suggest contacting CDC and FDA experts for advice. Your local county extension may be able to help as well.
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i got botulism from preserving some mushrooms. I feel like my life is over at this point. Over a year and a half on and my body malfunctions regularly. It’s so rare that GPs and neurologists have no advice for me. i can’t blame them since they’ve never dealt with it before
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I am so sorry to hear of your suffering. I did not encounter mushrooms as a source of botulism in the reading I did. You may have noticed in the article that scientists reportedly discover new sources of botulism poisoning every decade. It seems at times that we live in an increasingly toxic world. I wish you all the best and I pray for healing miracles.
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It’s no surprise that mushrooms would also carry C. botulinum spores since mushrooms are generally grown in soil.
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Yes, and thank you. I did find them listed awhile back and have added them to the article, though I doubt I’ll ever have a comprehensive list. Surprising how fast the information on the government web sites changes!
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Pingback: Healthy Living Link Party #107 | A Chat Over Coffee
Thank you! I am honored.
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Congratulations on being featured on Healthy Living Link Up. I have been freezing most of my vegetables – it easier and safer. We do make sauerkraut and can that but since it is fermented there should be no problems. Sharing on tweeter & pinning! Happy Spring!
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Thank you Marla. That was a nice surprise last night. Freezing is good! Were you surprised, as I was, that botulism outbreaks had been traced to some commercially frozen foods?
Thanks for the shares and well wishes. Happy spring indeed.
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Actually not a lot surprises me any more when it comes to commercial foods – just because I have learned not to trust so many manufacturers and there are so many people involved through the process. It does make you wonder how they mess up that allows the botulism bacteria to grow,
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Pingback: Love Healthy Recipes? Welcome to the Healthy Living Link Party #107
Thank you so much for featuring this article!
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Very informative. Thank you. I knew about the baked potato in aluminum foil, but not the others. The herbs in oil really surprised (and concerned) me! Thank you 🙂
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Yes, they did me too, because people had gifted such homemade infusions to us and we’d eaten them. Had we known!
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Any thoughts on olive brining? I have been doing it for years and all has been well. However this year we did a larger amount and I realized later that I didn’t step up my vinegar/salt ratio, which is what has me concerned. We have switched out the brine many times over the past year, but I am still hesitant.
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Good question. That is something I’ve never attempted. To get informed answers to your question, I suggest starting with the U.S. Center for Disease Control, which, in the article linked above titled “Botulism prevention: Many cases of botulism are preventable,” provides the following contact info.
800-CDC-INFO (800-232-4636), TTY: 888-232-6348
Email CDC-INFO
If you write a blog post about what you learn, do come back and share a link here. The more we can share safety tips the better, wouldn’t you agree?
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I only knew about honey. Thank you so much for sharing this important information!
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You’re welcome. Thanks for stopping by.
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I recently infused garlic and honey, left the mixture on counter top for about 2 days, then put it in the fridge. I ate a few pieces of garlic but stopped because I wasn’t sure about bacteria. I didn’t have a good glass jar, so I used a old food sauce jar and my honey mixture only filled it up half way…..is that bad??
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I cannot answer your question, “Is that bad?”, with any certainty, but I can tell you that I never eat anything that causes me to pause long enough to wonder if the food might be contaminated.
If you are concerned about botulism, I suggest you follow all the links in this article and, for good safety measure, contact an expert for advice.
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For all the years I lived in Iowa, I carefully followed the canning instructions for my cannig my garden’s vegetables. We are all still alive. But, nowadays, the only thing I can is fruit and jams.
Thank you for the article. Too often, what we don’t know can kill us!
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I know! As a young mom I canned dozens of fruits, tomatoes, jams and jellies every year, carefully following all the instructions. I thought I knew all the rules, but apparently they’ve changed over the years. Thanks for chiming in. I believe this is the first time I’ve seen you here, so welcome to my kitchen!
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Thanks for a well-researched informative article on C. botulinum! I’ve shared this on my Facebook page as I think education on this is so important.
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Thank you for sharing it. So important to spread the word about such dangers.
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Both were such excellent posts–the arsenic in rice and the C. botulinum. It would be silly for me to think about trying to write–or rewrite–when such good material exists. Thank you for all the work that went into those. I think we often fail to pay adequate attention to food safety.
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Hi Kathryn,
Thanks for the very informative excellent article – some of that I didn’t know. To be honest I would rather take my chances at eating homed canned vegetables than bought conventional vegetables that are many times filled with pesticides and all kinds of chemicals. I not sure that I trust the FDA or CDC completely as far as there information. If you would boil your home canned vegetables for 10 minutes – high heat destroys much of the nutritional value too. Thanks for sharing on Real Food Fridays. Pinned & tweeted!
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You’re welcome, Marla. So glad you brought up the heat issue. As you point out, boiling destroys valuable nutrients, as does the canning process itself. Plus, boiling ruins the flavor and texture. When possible, fresh is best. Thank you for sharing on Pinterest and Twitter!
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One thing I would like to mention, is that in your list you listed: Boil home-canned foods for 10 minutes before eating them. This does no good whatsoever. The bacteria is present when you initially prepare the home canned item. It then consumes the low acid mixture, and as a by-product of it’s metabolism excretes the toxin into the food. The spores and bacteria are harmless. It is the toxin they leave behind that is deadly. Therefore boiling the canned item after the fact will have no effect, the toxin is already present and boiling does not destroy it.
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Thank you for sharing your thoughts on the CDC’s recommendation to boil the food for ten minutes or more, depending on elevation. I checked their web site again today, and they continue to include that instruction in their list of ways to prevent the disease. I am not a scientist. I have to rely on their assessment in this matter. If you are a scientist who has access to new data/research, would you please share a link, and especially anything that may have been provided to the CDC. Perhaps they need to update the information they are providing to lay consumers such as myself.
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Raising the temperature to 185F for 5 minutes will, in fact, denature/render harmless toxins. The spores are more resistant to heat, but the toxin can be killed fairly easily.
Source: World Health Organization: http://www.who.int/mediacentre/factsheets/fs270/en/
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Thank you for that additional link and information, Kai.
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Kate, thank you for this carefully researched, clear explanation of these 12 foods that can cause botulism. Potatoes baked in foil? Canned tomato products? I had no idea! I’m grateful to you for sharing this potentially life-saving information.
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My pleasure, Margaret, and you know how grateful I shall ever be to you for spotting my rosemary-in-oil boondoggle.
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