Learning how to can tomatoes is a great way to store the abundance you may be getting from your garden! Whether you’ve spent the time and effort of growing tomatoes in your backyard or you purchased them from a local farm, don’t let any of them go to waste. I’m going to show you my easy, step by step instructions for how to can tomatoes; including supplies and equipment needed, how to fill the jars, how long to process them, and what to use them for later.
POP! The Best Sound Ever Heard in a Kitchen
If you’ve ever canned anything, you know exactly what I’m talking about. After all the prepping food, filling jars, carefully lowering into the water and trying not to get burned getting the jars out, while they’re sitting on the counter, you start to hear:
It’s the sound of something done right, of a process accomplished. You breathe a sigh of relief and listen joyfully.
The jars are sealing.
The first time I tried canning I jumped in and did pickles and salsa based almost entirely on verbal instructions from friends at my book club along with their quickly written recipes. It was a bit cheeky not to read up more on the process, I suppose, and I was deadly nervous about the whole thing, but that POP was the best sound ever at the end. I knew I had done it more or less correctly, and it felt great.
My grandmother and I then did a half bushel of tomatoes, and I picked up some more good tips. If you’re a beginner in the world of canning, this post is for you.
Equipment You Need for Canning Tomatoes
You will need some basic supplies in order to properly and safely can tomatoes. My canning pot is actually just a gigantic pot that looks exactly like a canner, but with a flatter bottom. It’s what I make my chicken stock in and is also sold for cooking corn, lobsters, etc.
Basic Canning Supplies Needed:
- water bath canning pot (approx 20 quart size)
- canning rack/insert if your pot didn’t come with one (this keeps them from bumping into other jars inside the pot and breaking)
- canning jars (simply choose your favorite size – I like quart jars for tomatoes)
- lids (if you’re reusing jars and need new lids)
- canning funnel (I invested in one after a few years and wondered why I waited so long!)
- magnet stick (used to handle the hot lids and rings – you can also use tongs instead)
- jar lifters
The canning funnel and magnet stick are optional, but they do make canning even easier!
If you want to can anything other than fruits, salsa, and tomatoes (i.e., meat, beans, green beans, other vegetables) you need a pressure canner to do it safely. The All American brand pressure canner is recommended as one of the safest and best out there.
Note: Did you know some canning lids are lined with BPA plastic? If you’re looking for an alternative, try Tattler reusable, BPA-free lids on Amazon (or here) or make sure to purchase the Ball BPA-free lids as they recently began offering these.
How to Can Tomatoes Properly
Once you’ve figured out what type of tomatoes you want to can (paste tomatoes are best for sauce while any large tomato is great to dice) and have either spent the summer tending a garden or picked up a bushel or two from a local farmer, it’s time to get started canning!
1. Gather all your Supplies the Night Before
Make it super easy on yourself and get all of your supplies cleaned up and ready to go. (Clear off the kitchen counters too!) Trying to can tomatoes, especially if it’s your first time, you definitely don’t want to deal with cluttered counters or the extra rush of finding the equipment you need when you’re in a rush.
Inspect the tops of the jars for cracks and run the jars and rings through the dishwasher on high heat to sterilize, preferably ending the cycle right about the time you need them so they’re still warm (easier said than done in a household with children).
2. Get the Pots Ready on the Stove
You will need three pots:
- water bath canner
- small pot for your lids to simmer in hot water
- nice large pot for cooking the diced tomatoes (8-quart size if you have it)
Fill your water bath canning pot about two-thirds to three-fourths of the way with water, depending on the size of your jars. You’ll want the water to cover the submerged jars by about an inch. Turn that on high to get it boiling as this will take a while (lid on helps it boil faster!).
Put your lids in the small pot and bring it to a simmer, not a boil, and leave a burner open at the front of the stove for your pot of tomatoes.
3. Start Prepping Tomatoes!
Start a pot of water boiling while you wash up all of the tomatoes. Once the water is boiling I like to remove the skin. This way the skins don’t separate from the pulp while you’re processing them and I just don’t prefer the way this looks. (If you’re blending the tomatoes to make canned tomato sauce, feel free to skip this step.)
A really easy way to get the skins to slide right off is to put 5-10 washed tomatoes in the boiling water for one minute or so. Take them out with a slotted spoon and put them in a colander where you’ll run cold water over them. The skins just slip right off with a paring knife or even just your fingers.
The next step is to core the tomatoes, which is really simple with a paring knife or even just your fingers.
Next, you can dice or chop them and put the pieces in a big pot to cook/simmer. My grandma doesn’t use a cutting board but rather just hacks the tomatoes apart in midair over the pot with a paring knife, like you might when slicing an apple or peach. Don’t do it like Grandma if you don’t have the right knife skills, I just mean to say that they don’t need to be pretty. 😉
4. Get ’em Boiling on the Stove
Go ahead and pour out the boiling water you used to remove the skins and start putting your diced tomatoes in it to cook. You’ll want to get them up to boiling temperature.
At this point, the water in your canning pot should be boiling; in fact, you probably have had to turn it to low and make it wait for you. That’s okay. Better it waiting than you, especially if bedtime is approaching.
Safety note – If you are canning tomato juice or puree, make sure to boil for at least 5 minutes to assist in removing air pockets before canning.
To expedite the process, you can fill the first set of jars as soon as you have enough tomatoes ready for them, then continue to chop tomatoes into the pot as round one processes in the canner. (Process is the canning word for boiling the jars for the appropriate amount of time for them to seal.)
How to Fill the Canning Jars
This is the part where my heart starts racing a little bit. Up until this point, you can be interrupted by kids, the phone or even dinner, but for about 10 minutes here, it would be best if you were focused (Hence the 10 p.m – midnight canning at my house).
Prepare the following supplies on the counter near your canner:
- rings (the lids should already be in hot water on your stove)
- funnel if using
- tongs or magnet thingy to get lids out
- clean, dry washcloth
- 1/2 or 1 tsp measuring spoon
- salt (I prefer Redmond) in a little dish
- lemon juice or citric acid
- oven mitt (to move the warm jars once filled)
5. Fill the mason jars with hot tomatoes
This is where the canning funnel comes in handy! You’ll need to use a ladle and pour the tomatoes into the jar. The best practice is to use hot jars as it reduces the risk that they will break (hot liquids + cold glass = breakage), so right out of the dishwasher is great.
Do not fill all the way to the top, but leave 1/2 inch of headspace and wipe off any sauce from the rim!
6. Add Salt
Put 1/2 teaspoon of salt per pint or 1 teaspoon per quart, preferably coarse or kosher salt into each jar of tomatoes. I usually use Celtic sea salt or Real Salt. If you’re a forgetful person like me, you may want to put the salt and acid (below) in the jars first, all at once. With quarts, I added 1/2 teaspoon at the bottom of the jar and 1/2 teaspoon at the top.
7. Add Lemon Juice or Citric Acid
This is necessary because so many types of tomatoes are “low-acid” nowadays and the proper acid levels prevent botulism!1 Add 1 Tablespoon lemon juice or 1/4 teaspoon citric acid per pint (double for quarts).
8. Put the Lids and Rings on Each Filled Jar
Double-check that there is nothing on the rim of the jar. Pull a warm lid out of the simmering pot with tongs or a magnet stick and place it on the jar, then tighten the ring (not as tightly as you possibly can, just a quarter turn or so past “on”).
9. Get the Jars into the Canner
Using an oven mitt (the jars are hot!) balance the jars on the rack inside the pot. Put them in as you fill them, and you want to get them all in quickly so you can get the jars processing as soon as possible. Keeping everything hot is important.
Lower the jars, make sure the water is about an inch over the tops of the jars (i.e. the jars are totally submerged plus some), put the lid on the canner and bring to a boil.
Now the kids can bug you if they need something. 😉
10. Process the Tomatoes in the Water Bath Canning Pot
The boil will take longer than you think. Do not start your timer until you have a genuine, rolling boil. Process for 40 minutes for pints, 45 minutes for quarts.2 When the timer goes off carefully lift the rack and hang it on the sides of the canning pot. Important note: If you live at altitude above 1000 feet, please consult an official guide for proper timing adjustments.
Use a really good oven mitt or the jar lifters from your canning equipment to get the jars out, setting them on a towel spread out with at least an inch between jars on your counter. I prefer the Ove’ Glove for jobs like this since I never invested in a proper jar lifter.
Now is the fun part, you get to hear those lids pop! Within an hour, and often in the first 5-10 minutes, the jars will begin to seal. Leave them at room temp for 12-24 hours. Write the month and year on the lid and let them cool. Now you’ve got food for the winter!
How Long do Canned Tomatoes Last?
For the best long-term results, your jars of tomatoes should be stored in a dark place with temperatures ranging from 50 to 70 degrees. As long as the lids have properly sealed, they should last well for 12-18 months. You will, however, see the best color and texture during the first 3-6 months.
As long as they stay sealed, they should remain safe to eat, but the quality will begin to degrade past 12-18 months. I’ve also heard that some people find they bring on a metallic taste after about 18-24 months.
After you open one of the jars, place any leftovers in the refrigerator, and use within 7 days.
If any of your jars do not seal properly, refrigerate, and use within a week.
What Can You do with Home Canned Tomatoes?
Having diced tomatoes on hand is so nice and convenient! It includes the pieces of firmer diced tomatoes you can use in recipes, but it also contains the lighter tomato juices which can be used as broth substitutions.
Easy recipes that use diced tomatoes:
- Keto Chicken Curry (add them in for some extra veggies)
- Sloppy Joes
- Nourishing Salsa Soup
- Slow Cooker Chipotle-Style Beef Barbacoa
- Add them to skillet cooked chicken, salt and pepper to taste, simmer, and top with mozzarella cheese and fresh basil!
- Stuffed Cabbage “Un-Rolls”
- Vegetarian Quinoa Chili or your favorite chili recipe
If you don’t have any canned tomato sauce on hand you can also blend two pints of diced tomatoes for every two cups of sauce needed and simmer it down into tomato sauce. Just season and use it in your recipe!
The Big Question: Why Can Tomatoes?
Are canned tomatoes nutritious?
For most vegetables and all fruits, heating does reduce the nutrients and high temperature/pressure often renders the produce far less nutritious than fresh or frozen. Tomatoes, however, release their lycopene when heated and the finished product contains more of this nutrient than in its raw state.3
Plus, I’m going to continue to buy canned tomatoes if I don’t make my own.
Does it save money to can your own tomatoes?
After the cost of the jars, new lids each year, and purchasing tomatoes, not to mention the energy used for the stove, canned tomatoes are pretty close to the same price as a good deal at the store. This was incredibly disheartening the first time I spent 4-6 hours canning tomatoes, then realizing I probably saved all of 50 cents! I vowed never to can again, unless by some chance I had a tomato harvest from my own garden.
Now that I try to buy tomatoes in glass jars (to avoid the BPA cans), I can save about half the cost.
Tips for Making Canning Tomatoes a bit More Frugal:
- Grow your own tomatoes! This is, of course, the cheapest way to get bushels of tomatoes for preserving without spending a lot of money.
- Check with your local farmers stand. Many times local farms will have a lot of “misfits”! The tomatoes are great for canning, but aren’t pretty enough for them to sell as slicing tomatoes. This way you can often get tomatoes for about half the normal retail price.
- Ask around for canning supplies. So often people have canning equipment lying around that they haven’t used in years and they’d love to pass it on to a friend or family member that will use them.
- Make sure to check garage sales! This is a great way to purchase supplies without spending a lot – always be on the lookout for jars too. (For safety purposes, make sure they are jars meant for canning.)
- Borrowing from a friend is a great way to get started with canning. Sometimes harvest happens all at once and people that do a lot of canning won’t be able to lend out their equipment, but it never hurts to ask!
If you are interested in learning more about canning different types of food I’d recommend the book Ball Complete Book of Home Preserving. It’s a great resource to have on hand and follows all of the modern food safety protocols.
- Home Canning and Botulism. (2018, June 11). Retrieved May 5, 2020, from https://www.cdc.gov/features/homecanning/index.html
- Selecting, Preparing and Canning Tomatoes. (n.d.). Retrieved May 5, 2020, from https://nchfp.uga.edu/how/can_03/tomato_water_pack.html
- Turning Up The Heat On Tomatoes Boosts Absorption Of Lycopene. (2008, August 22). Retrieved May 1, 2020, from https://www.sciencedaily.com/releases/2008/08/080820163109.htm