What’s Inside: In this article, I share 9 canning mistakes that can kill you. If that thought scares you, it should. However, canning safely is easy, when you follow safe canning principles. After reading this article, you’ll know the canning mistakes to avoid, so you can safely can with confidence.

Many people fear home canning. And it’s true. There are home canning mistakes that can kill you, or at least make you very sick.

This doesn’t mean that you should be afraid to home can. Home canning is very safe, as long as you follow safe canning practices.

In this article I cover some home canning mistakes that can kill you, and how to avoid them.


Key Takeaways

  • Until you’re an experienced canner, don’t make up your own canning recipes.
  • Don’t use thickeners that aren’t approved for canning, and only use thickeners that are approved in the right types of canned food and in the right amounts.
  • When canning in an altitude above 1,000 feet, be sure to adapt canning recipes based on your altitude.
  • When your jars have processed for the amount of time indicated on the recipe, don’t do anything to hurry up the cooling process.
  • Use pressure canners for low acid foods, and water bath canners for high acid foods.
  • Pressure cookers that don’t have a canning function aren’t safe for canning.
  • Adding extra vegetables to salsa recipes can reduce the acid level, which makes it unsafe for canning.
  • Don’t water bath can tomatoes without adding additional acid.
  • When following a hot packing canning recipe don’t allow food to cool down before canning it.

Home Canning Mistakes that Can Kill You

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Now without further ado, let’s get into the home canning mistakes that can kill you – and how to avoid them. By the end of this article, you’ll be able to can food at home with confidence, knowing you are following safe canning practices.

Keep reading, to dive into all the details of how to can safely at home.

Canning Mistake #1: Making Up Your Own Canning Recipes

Pro Tip: One of the best ways to avoid making mistakes with canning recipes is to follow a trusted guide such as The Ball Complete Book of Home Preserving (on Amazon).

Let’s say that you have a favorite chicken pot pie filling recipe that you would love to add to your prepper pantry. Should you make up a big batch, and can it? Maybe. But unless you understand safe canning principles, you may inadvertently can something that isn’t safe.

There are a couple of ways to avoid illness or even death when it comes to canning recipes.

Follow Tested Canning Recipes

The first option is to only follow tested canning recipes found on sites such as the National Center for Home Food Preservation. Recipes on those types of sites, are safe for canning, because they have been thoroughly tested.

But let’s get back to the chicken pot pie filling example. How can you safely can that at home? Later in this article I explain that using thickeners is one of the canning mistakes that can kill you. And since chicken pot pie filling is thick, it’s unsafe to can.

For Safe Canning, Add the Thickener Later

Having said that, you can safely can your chicken pot pie filling minus the thickener, and then add the thickener when you want to use it. When it comes right down to it, this is the same thing as canning chicken soup.

First, can an approved chicken soup recipe. Then when you’re ready to make your chicken pot pie, heat up the “soup” and add thickener such as corn starch or a roux made with flour to thicken the soup.

While this process isn’t as easy as opening a can of already thickened chicken pie filling, it gets you half-way there. By the time you’ve heated the oven and gotten the pie crust ready, your home-canned chicken pie filling can be thickened and ready to go.

As you gain experience, you can use your own recipes but only if you understand the principles that govern safe canning.

Canning Mistake #2: Adding Unapproved or Extra Thickeners When Canning

A picture of chicken pot pie. Chicken pot pie filling is thickened, but adding thickeners to the filling before canning it is a canning mistake that can kill you, so please don't do it!
Don’t add thickeners when canning things like chicken pie filling. Instead, add thickeners right before using.

In the chicken pot pie filling example above, I mentioned the dangers of adding thickeners when canning.

Too much, or the wrong kind of thickeners, can make it more difficult for heat to penetrate the food you’re canning. Without proper heat penetration for the appropriate amount of time, botulism risk increases.

“Unapproved thickeners” extend beyond thickeners such as flour and cornstarch. Food such as rice, noodles, barley, and dumplings should be avoided. If you want to include a starch such as noodles in a canned soup, wait until you plan to serve the item to add the starchy item.

The exception to this is that it is safe to can peeled and diced or cubed potatoes.

There are also approved thickeners that can be used for canning such as Clear Jel (Amazon). However, Clear Jel has only been approved for thickening pie filling. You also need to use approved amounts of the thickener.

Canning Mistake #3: Not Adapting Canning Recipes for Altitude is Unsafe

a picture of a mountain range.
Adapting canning recipes for altitude is an important part of canning safely.

Altitude impacts both pressure canning and water bath canning. Most canning recipes are based on altitudes of lower than 1,000 feet or 305 meters above sea level. If you are in an altitude higher than that, you must adapt canning recipes based on your altitude.

pressure valves for the Nesco smart canner. Use the green valve if you are canning at an altitude higher than 1,000 feet.
Depending on the type of pressure canner you have, there are ways to add more or less pressure, based on your altitude. In the case of the Nesco canner that I use, there are two different pressure weights that come with the canner. The black valve is for canning in altitudes under 1,000 feet. I use the green valve, since I can at an altitude above 1,000 feet.

With pressure canning, you adapt recipes by adding more pressure. In a lower altitude, when using a pressure canner with a weight, use a weight for 10 pounds of pressure. If you’re canning in an altitude above 1,000 feet, you need to use 15 pounds of pressure.

You also need to adapt water bath canning recipes if you’re in an altitude higher than 1,000 feet. For instance, if you’re between 1,000 feet and 3,000 feet, add an additional five minutes of processing time to water bath recipes.

The reason this matter is because water boils at a lower temperature in higher altitudes. It’s important to adjust canning recipes for altitude because if you don’t, the food you’re canning won’t be processed long enough to kill microorganisms.

Pro tip: To gain a better understanding of how altitude impacts canning, be sure to check out my article, How Altitude Impacts Canning | How to Adapt Canning Recipes Based on Your Altitude

Canning Mistake #4: Hurrying Up the Cooling Process

All canning recipes include the appropriate amount of processing time. For instance, according to the National Center for Home Food Preservation, the processing time for canning beans is 75 minutes for pints and 90 minutes for quarts.

It’s important to note that this processing time takes into consideration the time that heat and pressure remains in the canner during the time when the canner is cooling down. You may have noticed that until the pressure drops, you’re unable to open the lid on the canner.

If you’re in a hurry, you may be tempted to remove the pressure weight (or in the case of the Nesco canner (Amazon), turning the pressure valve from airtight to exhaust). Removing the weight does indeed cause the steam to shoot out of the canner much faster.

pressure valves for the Nesco smart canner. This makes this device safe for canner, as long as you use the right valve, based on your altitude.
In the above photo you can see both airtight and exhaust indicators. When pressure canning, leave the valve in the airtight position after the canning process completes, to let the pressure come down naturally.

I understand the temptation to hurry up the cool down process when canning. However, doing so results in your canned food being under-processed, and thus unsafe.

It can also cause siphoning (liquid coming out of the jars). In some cases, the rapid change in temperature may also cause jars to break.

Allow the Pressure to Come Down Naturally

Because of this, it’s important to allow the pressure to come down naturally before attempting to remove the canner lid. In my experience, this takes anywhere from one hour to 90 minutes.

The time that it takes to come down from pressure naturally is often as long or even longer than the actual canning process. Therefore, it’s important to take that amount of time into consideration before starting a canning project.

As an example, I don’t pressure can anything unless I’m going to be home for at least three to four hours. I also don’t start canning anything when I’m hoping to go to bed within the next couple of hours.

Pressure canning is a time-consuming process, and it’s best to do it when you’re not in a hurry.

Canning Mistake #5: Using the Wrong Type of Canner

Water bath canning is only safe for high-acid foods. Using a water bath canner to can low acid foods such as meat is a canning mistake that can kill you.
Water bath canners should only be used for canning high-acid foods such as fruit, pickles, and salsas.

There are essentially three types of canners that are approved for home canning, all of them available on Amazon:

Each of these types of canners are to be used in specific ways, for specific types of food.

Pro Tip: To better understand the difference between pressure canners and water bath canners, read my article, Pressure Canning Vs. Water Bath

Both water bath canners and steam canners can be used for high acid foods such as fruit. It’s important to use pressure canners for low-acid foods such as beans, meat, and most vegetables.

Some people swear that you can use water bath canners for low acid foods such as the ones mentioned above. This topic arises a lot from both people in the United States who only have water bath canners, as well as from people in Europe, where pressure canners are hard to come by.

Why You Shouldn’t Water Bath Can Low-Acid Food

It is true that you can safely water bath can low acid foods. However, it’s not nearly as safe nor as convenient as pressure canning.

RoseRed Homestead

In the above video, RoseRed Homestead demonstrates the folly of attempting to use a water bath canner for canning low-acid foods. She explains the algorithm used by the food industry to determine the temperature needed to kill botulism spores. She used that information to figure out how many hours it would take to safely water bath can low-acid foods. Here’s what she found:

  • For those at sea level, you would need to water bath can low acid foods for a minimum of six hours
  • At a higher elevation, such as 5,000 feet, you would have to water bath can low acid foods for a minimum of 18 hours

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You have to ask yourself if you really want to process food in a water bath canner for so many hours, when you can safely process the food in a pressure canner for much less time.

Pressure canning is the safest and most efficient way to get foods into the kill zone when canning so that the risk of botulism is decreased, if not eliminated completely.

Canning Mistake #6: Using Pressure Cookers Instead of Pressure Canners for Canning is Unsafe

There can be a lot of confusion when it comes to understanding the difference between pressure cookers and pressure canners.

There are a few differences between pressure canners and pressure cookers. Once you understand those differences, you can see why pressure cookers aren’t safe for pressure canning.

Pressure Canners Have Minimum Size Requirements

The first difference is size. Pressure cookers are often smaller than pressure canners. The size difference matters because with a smaller size, both the heat up and cool down times are less in pressure cookers. This causes a similar problem under the point related to speeding up the cooling process mentioned above.

The shorter processing time can result in under-processed food, which can lead to botulism.

The other difference between pressure cookers and pressure canners has to do with regulating the amount of pressure. Pressure canners have weights that regulate the amount of pressure during the entire processing time.

Multi-Use Devices that Are Safe for Canning

The Nesco Smart Canner (Amazon) has a similar mechanism in that it has two different valves available, one for 10 pounds of pressure for those in a lower altitude, and one for 15 pounds of pressure for those in altitudes above 1,000 feet.

The weight (or in the case of the Nesco, a valve) is missing on pressure cookers, and because of that, they don’t maintain the right amount of pressure during the processing time.

Without the weight or valve, it’s impossible to ensure that your food has been processed long enough and because of that, it’s unsafe.

Please note that some people claim that it’s unsafe to can in the Nesco Pressure Canner and Cooker since it can be used for things other than canning, but that’s not the case. Having multiple bells and whistles doesn’t make a device unsafe for canning. The key is that it has features that are specifically used for canning.

Canning Mistake #7: Adding Extra Vegetables to Salsa Canning Recipes

tomatillo salsa using an approved canning recipe. If I added more onions or peppers to it, it would not be safe for canning, due to the lowered acid level.
Peppers and onions are a delicious addition to salsa, but when canning adding extra onions and peppers can throw off the acidity level, and make the salsa unsafe for canning. In the image above, I added peppers and onions based on a safe canning recipe.

If, like me, you like to wing it when you cook, when canning, you may be tempted to throw in extra onions, peppers, and other vegetables to salsa recipes.

As an example, let’s say that you’re using this salsa recipe on the Fresh Preserving site. In addition to vinegar and a few other ingredients, the recipe calls for 10 cups of cored, peeled tomatoes, 5 cups of seeded bell peppers, 5 cups of chopped onions, and 2 1/2 cups of seeded chili peppers.

Perhaps you really love onions, or you want more heat that comes from peppers. Is it okay to add extra onions or peppers? Or maybe you like corn in your salsa, and want to throw in a couple cups of corn. Is it safe to do that? In a word, no.

Salsa Needs to be a High Acid Food to be Water Bath Canned

The reason for this is that most salsa canning recipes are water bath recipes. As such, they require the food you can to be high-acid. In the case of this salsa recipe, both the tomatoes and the vinegar provide the right amount of acidity to make this recipe safe for water bath canning.

If you add additional low-acid foods such as corn, or more peppers and onions, you risk decreasing the level of acidity, and thus make the salsa unsafe to water bath can.

Especially if you’re newer to canning and don’t know how to safely adapt recipes, for safety reasons, it’s best to stick with approved canning recipes.

Canning Mistake #8: Water Bath Canning Tomatoes without Adding Acid

ingredients for canning cherry tomatoes include salt, cherry tomatoes, and lemon juice.  The lemon juice increases the acid level, which makes the recipe safe for canning.
When I canned cherry tomatoes, I added salt for flavor, and lemon juice to bring up the acid level. Salt is optional, the lemon juice is not, unless it’s replaced with one of the acid types listed in the table below.

Tomatoes are often water bath canned. This is true when it comes to water bath canning salsa, canned tomatoes, tomato sauce, and so on.

One reason it’s safe to water bath can tomato-based recipes is because of the acidity level. However, the acidity level in tomatoes varies. If the acid level is too low, botulism can occur.

The good news is, it’s easy to add acid to tomatoes. You can add lemon juice, citric acid, or vinegar when canning tomatoes.

Chart for Adding Acid when Canning Tomatoes

Check out the table below to know how much acid to add when canning tomatoes.

Acid TypeJar SizeAmount
Lemon JuicePint1 Tablespoon
Lemon JuiceQuart2 Tablespoons
Citric AcidPint1/4 Teaspoon
Citric AcidQuart1/2 Teaspoon
5% Acidity VinegarPint2 Tablespoons
5% acidity VinegarQuart4 Tablespoons

Pro tip: If using citric acid, be sure to use food grade citric acid such as this Ball Jar Citric Acid on Amazon.

Note that vinegar impacts the taste of the product more than lemon juice or citric acid, so I personally recommend only using it if you really like the taste of vinegar or if you have no other choice.

Canning Mistake #9: Allowing Food to Cool Before Canning

When you look at the canning recipes or instructions on sites such as the National Center for Home Food Preservation, you’ll notice that the instructions often include the words “hot pack” or “cold pack.”

What this essentially means is whether the product you’re canning is hot or cold when you put it into the jars. If the chart or recipe you’re following calls for “hot pack” the assumption is that the food is hot when you put it into the canner. The processing time in the recipe is based on that assumption. So, if the food you’re putting into the canner is cold instead of hot, the food may not process completely, and thus will be unsafe.

Questions about Botulism? We Have Answers.

Botulism is the biggest fear among home canners. It’s a valid concern, but it’s not common, especially when you follow safe canning principles as laid out in this article. Having said that, it is important to have a factual understanding of botulism. Here are some frequently asked questions about botulism, along with answers from trusted sources including The CDC (Center for Disease Control and Prevention), the New York State Department of Health and the Alaska Division of Public Health.

You may notice signs like a leaking, swollen or bulging can, unnatural color, bad smell, or spurting liquid when opened.

Symptoms may include difficulty swallowing, blurred vision, muscle weakness, drooping eyelids, and difficulty breathing.

Yes, boil meat and vegetables such as corn and spinach for 20 minutes, and all other low acid foods for 10 minutes to destroy botulism toxins.

Properly canned food should have an intact seal, no leakage, and no signs of spoilage like discoloration or foul smell.

Food contaminated with botulism may appear and taste normal, making it difficult to detect by taste alone.

Symptoms typically appear within 18 to 36 hours but can sometimes show up several days after exposure.

Follow the Instructions!

The bottom line is that home canning can be done safely. Following instructions from trusted sources helps ensure you don’t make potentially deadly canning mistakes.