Frequently Asked Questions About Canning

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Questions about canning arise all the time. I’ve taken the time to answer the most frequently asked questions about canning.

When I first started canning, I had no idea what I was doing. I read the directions for the canner, I read everything in the recipe, and I read tips from the Ball Blue Book Guide to Preserving. But I still had questions.

I’ve since grown used to canning, and don’t have questions nearly as often as I once did… but I know some of you may. That’s why I decided to put together this list of the most frequently asked questions regarding canning.

If you have a question that is not on this list, please leave me a comment below. Not only will I answer you directly, but I’ll also add that question to this FAQ for future readers.

General Questions About Canning

Presto 01781 23-Quart Pressure Canner and CookerIs pressure canning safe?

Yes. Pressure canning is perfectly safe so long as you follow the process as described by your recipe.

Is water bath canning safe?

Yes, as long as you follow the instructions in the recipe, the process and the results are one-hundred percent safe.

How long does home canned food last?

Typically, you’ll find people say one year is the “best by” date, but I’ve known people to go 3, 4, even 5 years before popping the lid. Use your best judgement. Try 6 months, then a year, then a year and a half. Honestly, I wouldn’t go more than 2 years before eating the food (unless there was a dire emergency and I had to make my supply stretch).

Will canning kill salmonella?

Salmonella and other such bacteria can survive certain levels of acidity and can thrive in a sealed jar, but they cannot survive the extreme temperatures during the canning processing.

Why can’t I water bath can meats and vegetables?

Granite Ware Covered Preserving Canner with Rack, 12-QuartLow-acid foods like beef, pork, chicken, fish, and most vegetables (with the exception of some tomatoes) can support the growth of Clostridium botulinum – the deadliest food poisoning known to man. The temperature inside a pressure canner reaches 240-250°F or higher which will kill the spores that produce botulism toxins. A water bath canner only reaches temperatures around 212°F – the boiling point of water.

Can canning be done in an Instant Pot?

No. While there are specific “canning” pots from companies who make digital pressure cookers, it has been shown multiple times that an Instant Pot does not achieve the temperatures needed to safely can low-acid foods.

What canning supplies do I need?

You’re going to need a canning pot of some sort, but what you actually need there depends on what type of canning you’re doing. If you have a good pressure canner, you can actually water bath can with it as well as pressure can, but they’re a bit more costly than a water bath canner. You’re also going to need jars, lids, rings, and accessories that will make the canning process much easier and faster.

Get a better idea of what supplies you need here: The Most Essential List of Canning Tools You’ll ever Need

Why is canning important?

Preserving food in general is a good idea for a few reasons. You’re making sure you have food for the future, you can control what additives go into the food, and you know where the food came from that you’re about to eat.

Canning, however, is probably a more important preservation method than any other. The main reason is you need no electricity to process or store your canned goods. While freezing is a faster method of preserving fresh food, it’s all for naught if you lose power for any extended period of time.

We’ll talk more about canning vs other methods of preserving in another article. There’s a lot to talk about.

Questions About Canning Lids and Rings

Pressure canned jars of chicken stock.When canning, should the lid pop?

Yes. Every time you can food at home, you will typically hear a “pop” or a “ping” as the lids seal. The lids are raised in the middle, so when the suction has pulled all of the air out of the jar, the lid will pop down causing the familiar “ping” that canners love to hear so much.

What should I do when the canning jars don’t seal?

This one is a little tricky. Some people will tell you that any jar which does not seal must immediately be refrigerated and eaten within the week. Others will tell you that you should reprocess those jars. We play it by ear.

If there’s one jar in the whole bunch that doesn’t seal, we’ll refrigerate and eat what’s in that jar in a few days. If there are multiple jars (usually 3 or more) that don’t form a seal, we’ll evaluate what happened, remove the lids, check the headspace, clean the jar rims again, put on a new lid and ring, and process those jars again.

What causes canning jars not to seal?

Wiping the rim of a jar with white vinegar.Chips in the rim, cracks in the jar, and unclean rims are your usual culprits when it comes to jars not sealing. Wiping the rim of the jar with a paper towel dipped in white vinegar lets you feel the rims of the jars for imperfections while you’re cleaning food particles and oily liquids off the rim. This typically ensures a seal will form.

However, there are cases where siphoning (food and liquid leaking out of the jar during processing because of improper headspace) causes the rim to get food or oil on it and not seal. There are also times when you just get a bad lid (it happens more than you hear about).

Are canning lids reusable?

That’s a trick question, and the answer I give will be in two and a half parts.

Yes, canning lids are reusable. You can safely use them to vacuum seal dry goods into jars using a Food Saver or other brand of vacuum sealer with jar attachment. You can also use those lids for anything you’re just putting a lid on to store in the fridge for a few days.

…and no, you cannot reuse canning lids. If you’re looking to put old lids onto jars for water bath or pressure canning, it is not recommended. You should always use new lids to ensure the best chance of a seal that does not fail.

[insert shifty eyes here]

Should I leave the ring on or take it off after canning?

Pressure canned jars of chili and ground beef.Most people will tell you this is all about personal preference, but I beg to differ.

Rings can allow an unsealed jar to reseal without you ever knowing. This can lead to bacteria and spoiling of your food. Also, why you shouldn’t stack your jars once sealed as it can do the same thing. Rust. Less need for more rings. First of all it came cause moisture and bacteria to grow around the seal and it can pop your seal but give you a false reading of the pot to seal. Food residue or water can hide under the rings and cause rust or bacteria growth. Just feels – to me – to be more hygienic to remove them and to wash off the threads around the top of the jar.

Questions about Canning Jars

Are canning jars microwave safe?

Most people will tell you Mason jars are safe to put in the microwave. Personally, we’ve never had an issue. However, I will warn you to be cautious and keep an eye out. Glass does react to heat, so I wouldn’t try to put a canning jar in the microwave for long periods of time, and never put one in straight out of the freezer.

Are canning jars oven safe?

The glass used in manufacturing Mason jars (at least the ones manufactured for Ball and Kerr) is not tempered for oven use. Don’t try to bake a loaf of bread or a cake in a canning jar. However, if you’re looking to sterilize your jars in the oven…

Can Mason jars be sterilized in the oven?

Warming Mason jars in the oven.Yes, they can. You should preheat your oven to 275°F/135°C, wash your jars in warm soapy water, and then rinse them, but do not dry them. Space your jars (so they’re not touching) on a clean sheet pan lined with a silicone mat. Put the tray into the preheated oven for about 10 minutes, and your jars are ready to go. Be careful with the tray so you don’t clink the jars together or against the metal pan itself for risk of breaking them.

Are canning jars freezer safe?

We use canning jars in the freezer a lot. Sometimes we make and freeze a quick batch of chicken stock when we don’t have time to actually can it. Other times, we’ve canned stock, but we have one jar that won’t fit, so it goes into the freezer. Just remember to only fill the jars about 3/4 of the way to allow room for the liquid to expand.

Will canning jars break in the freezer?

Yes, if they are filled with too much liquid and the lid is on tightly, it is very possible for a Mason jar to crack and break in the freezer. If you’re freezing liquid in a jar, it’s a good idea to leave the lid off or slightly ajar just in case. Canning jars are too valuable a commodity to us homesteaders to risk losing them.

Are canning jars airtight?

If the lid is sealed on, yes, canning jars are airtight. If you just screw one on, it may not be. However, if you process jars in a canner or use an attachment with your vacuum sealer to seal the lid, it is absolutely airtight.

What questions about canning do you have?

Still have questions about canning that you need answered? Ask them in the comments below! We’ll get you the answer and add the question to this post for future reference.

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15 thoughts on “Frequently Asked Questions About Canning”

  1. Thanks for answering these frequently asked questions about canning. I am surprised that you can freeze canning jars without them breaking. But I guess filling them 3/4 with food, allows room for expansion.

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