Unsafe home canning practices

The composition of a list of unsafe home canning practices will vary depending on who you ask, and how many people you ask.

There will be some major dangers on the list. No doubt, though, a committee could stretch the list to pages long with many additional minor or rare unsafe practices.

This list is just meant to be the high level, major items that reputable home canning authorities would agree upon.

If you are doing any of these, then chances are most safe home canners would say you are doing risky canning.

With those caveats in mind, Healthycanning.com proposes that the greatest unsafe canning practices are, in alpha order:

Contents hide

1 1. Aspirin or other pill canning
2 2. Compost heap canning
3 3. Crockpot canning
4 4. Dishwasher canning
5 5. Microwave-canning
6 6. Open-kettle canning
7 7. Oven-canning
8 8. Pressure canning via guesswork
9 9. Recipes — out of date or untested
10 10. Solar-canning
11 11. Water-bath canning instead of pressure canning
12 The greatest home canning danger of all
13 Further reading

1. Aspirin or other pill canning

“No to Canning Pills: ‘Canning pills’ went out with corset-covers. Old manuals might suggest that salicylic acid (read this ‘aspirin’) be dropped in each canning jar before it was capped. Such things never helped then and would not help now. No preservative added can offset dirty handling or inadequate processing.” ^[1] Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 61-62). Penguin Publishing Group. Kindle Edition.

2. Compost heap canning

“No to Processing in a Compost Heap. Whoever would have thought it? But there was a query based on the notion of holding containers of food at 140 + F/60 + C for a long time.” [Ed: by the heat generated in a compost heap.] ^[2] Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 62). Penguin Publishing Group. Kindle Edition.

3. Crockpot canning

“No to Canning in a Crockpot: We don’t know who could have advocated this, since we have never seen any such claims in print by the makers of Crockpots. But it has come up several times in letters to PFB, usually from writers who say they hope it’s safe, because they felt that slow-cooking was more likely to preserve nutrients than subjecting the food to heats like 240 F/116 C. All we need to say about a Crockpot is that if it’s on a long low-heat setting, chances are that the nastier micro-organisms will be encouraged to grow and breed like mad, and what else should you expect?” ^[3] Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 62). Penguin Publishing Group. Kindle Edition.

4. Dishwasher canning

Trying to “steam process” jars by the heat generated in a dishwasher during a dishwasher cycle.

Processing canned foods during a dishwasher cycle can be dangerous. The temperature of the water during the cleaning and rinsing cycle is far below that required to kill harmful microorganisms. Thus the product will be under-processed and unsafe to eat.” ^[4] PennState Extension. Canners and Canning Methods that are Not Recommended. Accessed March 2016.

5. Microwave-canning

See separate page on microwave canning.

6. Open-kettle canning

Just putting something in a bottle, slapping a lid on it, and if a seal takes hold, considering it done and putting it on the shelf.

See separate page on open-kettle canning.

7. Oven-canning

Taking a short-cut by trying to process bottles in an oven.

See separate page on oven canning.

8. Pressure canning via guesswork

Not following preparation and processing methods and times exactly, including any altitude adjustments required for your location. Following directions that you or someone else have just made up through guess work and reasoning.

9. Recipes — out of date or untested

Using out-dated recipes or untested recipes.

And from Isabel D. Wolf, of the University of Minnesota, about home-canning recipes: ‘avoid following the home-canning advice of celebrities, old cookbooks, ‘back to nature’ publications, and out-of-date home-canning leaflets. Some potentially dangerous instructions can be found in old official publications, even those of this state!’ ” ^[5] Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 45). Penguin Publishing Group. Kindle Edition.

10. Solar-canning

Using the heat of the sun to heat up a box in which you place the jars for procesing.

11. Water-bath canning instead of pressure canning

Water-bath processing low acid food products instead of pressure canning them

__________________

Past those points above, though, once you start to expand the list from there, internecine wars start to break out even amongst the “safe canning police” people about venial versus mortal sins.

The greatest home canning danger of all

Out of the above list, the greatest danger of all perhaps is in not pressure canning something that must be pressure canned:

…because in almost every account of an outbreak of food-borne botulism, the Editorial Note deduces that ‘inadequate processing’ or ‘inadequate heating’ allowed the toxin to form, with the help of a bad seal. Spelling it out, this means that low-acid foods that should have been pressure-processed were merely given a Boiling–Water Bath; and that strong-acid foods—which should have been given a Boiling–Water Bath to sterilize container and heat contents adequately—were canned instead by “open-kettle,” or worse.” ^[6] Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 60). Penguin Publishing Group. Kindle Edition.


 All jars of home preserves must be heat processed
All jars of preserves meant for shelf-stable storage require heat processing of the filled, sealed jar. No matter how much you sterilize a jar in advance, cook the food before, or how much sugar or vinegar is in your recipe.
 Cowboy canners
Cowboy canners will stick anything in a jar, close the lid, stick it on a shelf to fester, then feed it to people. They purport to trust in the "good old ways" of canning, take delight in mocking any caution or safety practices, and approach canning with...
 Do not use Mason jars as meatloaf grease grabbers
An Internet "tip" has emerged which involves using a Mason jar as a "grease grabber" to suck up grease out of meatloaves. Both Ball and Bernardin actively recommend against using their Mason jars for this.
 Fractional sterilization" or "intermittent processing
A bizarre canning method known as "fractional sterilization" or "intermittent processing" encouraged bacteria to colonize your jars of canning three days in a row.
 Home Canning Cured Meats (Bacon, Brined, Corned, Ham, etc)
Home canning authorities say not to home can cured meats. The issue is that curing changes the density of the meat, and that that changed density has not been tested for safety.
 Home-canned cake
You cannot safely home can bread or cake. If someone gives you home canned cake, assume it is unsafe to eat and discard it in a manner that not even animals can consume it.
 Inversion Canning
Inversion canning is not canning because no canning process has happened. Both open kettle canning and inversion have now been discredited and proven unsafe and are strongly recommended against.
 Microwave Canning
Do not attempt to use a microwave to do home canning in. The resultant product will not be safe. 
 Open Kettle Canning
Open-kettle canning is just putting hot food in a jar and slapping a lid on, with no further processing of the jars. It leads to a lot of food wastage and illness.
 Oven Canning


Promoted from time to time as a "new" home canning technique, "oven canning" is actually an old technique. It has been around since at least the 1920s -- and it has been discredited and advised against since the 1940s.

It involves "baking" your...
 Oven sterilization of Mason jars
Oven sterilization of jars for home food preservation is no sterilization at all, and is not safe. All food authorities including the actual manufacturers of Mason jars recommend against it.
 Why do you have to process jars of jam?
Some people ask why jars of jam must be heat processed after bottling, in either a hot water bath or a steam canner. Doing so provides a safer, higher quality product.

References[+]

References
↑1	Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 61-62). Penguin Publishing Group. Kindle Edition.
↑2	Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 62). Penguin Publishing Group. Kindle Edition.
↑3	Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 62). Penguin Publishing Group. Kindle Edition.
↑4	PennState Extension. Canners and Canning Methods that are Not Recommended. Accessed March 2016.
↑5	Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 45). Penguin Publishing Group. Kindle Edition.
↑6	Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 60). Penguin Publishing Group. Kindle Edition.

Comments

Jack Gilbert

August 12, 2022 at 7:22 am

Hello, I grew up in the USA but have moved to Spain. I want to start canning but they dont have mason jars here. What they do have are these, and I would liek to know if they are safe to use for pressure canning: https://www.amazon.es/Frasco-vidrio-conservas-720-Pack/dp/B06X15LFY1/?_encoding=UTF8&pd_rd_w=84OaL&content-id=amzn1.sym.e938e71b-2a18-43eb-855b-f4edce2ba725&pf_rd_p=e938e71b-2a18-43eb-855b-f4edce2ba725&pf_rd_r=VDZBM302G2Z0NC4KDCJ1&pd_rd_wg=joV8R&pd_rd_r=199f0e6f-819f-45e2-b750-ac3432009137&ref_=pd_gw_ci_mcx_mr_hp_atf_m

- Healthy Canning
  
  August 30, 2022 at 11:21 pm
  
  Consider look at Weck jars, Leifheit Jars, Quattro Stagioni jars or Kilner jars, all available in Europe. If you search Healthy Canning, you’ll find info on all those jars.
  
Geri

July 08, 2020 at 5:54 am

Canning with flour is an unsafe practice.

- Healthy Canning
  
  September 24, 2020 at 3:18 am
  
  UNLESS it is called for in a lab-tested recipe, in which case, it is then safe.
  
Brian Oskaar

May 05, 2020 at 12:15 pm

Thank-you for not mincing your words. So important.

jan

December 28, 2018 at 6:18 pm

On the “must pressure can only” part. That only applies in the usa, MOST countries don’t even have pressure canners and water bath everything aproximately 3 hours. You might want to note that in your list because usda fda do not rule for everyone lol.

- Healthy Canning
  
  September 11, 2019 at 3:28 pm
  
  The rules of science and of food safety know no borders. No amount of bluster and huffing and puffing about those “Americans” is going to change that.
  
- Ashley P
  
  October 01, 2020 at 11:40 am
  
  3 hours? All you do is wreck the nutrients of your food. No matter how long you hot water bath the temperature will never exceed 212 degrees Fahrenheit. Temps over 212 are required for low acid foods. Only temps over 212 can kill the kind of bacteria that dwell in a low PH environment. Reaching temps over 212 can only be done with a pressure canner. Pressure canners/cookers are used in many parts of the world not just USA. It’s science not a national identity thing
  
- Kentherlan
  
  February 15, 2022 at 10:04 am
  
  My late grandmother used a wash tub next to the creek and canned with an open fire for hours until it sealed. It didn’t kill her, my grandfather, my Aunts & uncles as childrennor me. I don’t have any problems with the old ways. I see it done in many parts of the world and they are alive and well.
  
  - Healthy Canning
    
    July 25, 2022 at 3:02 am
    
    “I see it done in many parts of the world and they are alive and well.” Except for the ones that dropped like flies. What you said is exactly like saying “Smoking is safe because I knew a woman who smoked a pack a day till the age of 90 and she never got lung cancer, and since she didn’t, no one else will either.”
    
kathy

February 24, 2018 at 2:38 am

Please help me I bought an electric pressure cooker assuming I could can in it. I am hearing mixed reviews and makes me nerves.

- Healthy Canning
  
  April 22, 2018 at 3:33 pm
  
  Regardless of what manufacturers may try to claim, all reputable home canning authorities are explicitly warning against using those machines for home canning. Many people who have tried report loss of food and work as the jars spoil on the shelves. https://nchfp.uga.edu/publications/nchfp/factsheets/electric_cookers.html
  
- Freddie
  
  June 07, 2019 at 10:31 pm
  
  Many of the electric pressure cookers do advertise safe canning but the government website strictly says it isn’t safe – the temperature inside the jars cannot get hot enough and you could get botulism from the contents. I bought one of the electric pressure cookers for canning – the ad on tv showed so many ways to can. But after reading on the government webpage for the guidelines, I never canned in mine – it’s great for cooking meats fast for dinner, etc., but not canning.
  
Colleen

January 23, 2018 at 1:02 am

How do you feel about substituting Yves Ground Round for ground beef in a soup recipe that is being pressure canned?

- Healthy Canning
  
  February 01, 2018 at 12:10 am
  
  Colleen, that is a soy product. We checked on that several years ago with the National Center for Home Food Preservation. There has not been any funding to test home canning soy meat anagrams so they have no recommendations to offer on that for safe canning. Nor do they know of anyone else in Canada or the US who has invested in any testing to arrive at safe processing recommendations. Sorry.
  
gg miles

February 17, 2017 at 4:55 pm

How long do herbed stewed tomatoes put hot into a clean mason jar last in the refrigerator?

- Healthy Canning
  
  February 19, 2017 at 6:14 pm
  
  So instead of canning them, you will just use the jars as temporary storage containers in the fridge? In that case, regular food storage rules would apply — 3 to 5 to 7 days, depending on who you read.
  
Arnold 7

February 08, 2017 at 12:49 am

Every time I do canning… It is not finished until pressure cooked ! just for safety sake .

- Healthy Canning
  
  February 08, 2017 at 10:06 pm
  
  Sadly, that’s just rolling the dice and you are probably better off saying a Hail Mary instead. Safety is following a tested recipe from a reputable source, exactly. “Pressure cooking” a jar of pickles won’t do anything except increase your cooking fuel bills.