Tomatoes are one of the many pleasures of the summer, and if you’ve ever had a ripe tomato fresh off the vine, you know it can’t be beat. I’m fully convinced that everyone should grow their own tomatoes, since they don’t require much space or water and give you so much for so little care!
However, you’ll quickly learn that tomato plants fruit like crazy and you’ll soon be swimming in tomatoes. Some people were lucky enough to grow up in a family of home canners and have been canning and preserving foods all their life, but that’s not most of us.
I understand that it can be daunting to begin to learn how to can- I started from absolutely zero prior experience or knowledge and am completely self-taught, with the help of lots of internet resources of course!
One fantastic resource is the National Center for Home Food Preservation, whose website shares lots of information about correct temperatures, measurements, and techniques. Plus tons of ideas of how to preserve!
Why Can Tomatoes
Tomatoes fruit so profusely that many beginner gardeners have so many that they don’t know what to do with them. Tomato plants are so plentiful and this is why there’s so many ways to preserve tomatoes so that we can enjoy them all year long.
Plus, once you’ve eaten fresh tomatoes straight from the garden, you just can’t support eating store bought and imported tomatoes in the dead of winter.
This is why generations of farmers have developed- and continue to develop- methods for preserving like sun drying, dehydrating, canning, pickling, and even just freezing. When tomatoes are canned properly, they have a shelf life of at least one year!
Canning tomatoes is a way to easily preserve tomatoes so you can enjoy that fresh taste and seasonal produce, all year long. So, let’s get into this step-by-step guide for canning tomatoes for beginners.
There are a few things you’ll need to get started, but most of these are common kitchen items that most beginner cooks and gardeners will have anyways!
- Jars! Even though we say “canning,” glass jars are the easiest to come by and work with. Regular mason jars are great for this but the main requirement is that you have lids for all the jars.
- Funnel with a wide mouth funnel will allow the tomato chunks to go in and makes pouring in the sauce much easier.
- Tongs with a good grip to carry the hot jars, you really don’t want any jars filled with sauce to drop and break!
- Cutting board, a flexible, plastic cutting board really helps transfer the tomato pieces into the jars. Don’t use a wooden cutting board, because this can have bacteria living in the little grooves.
- Large pot that can fit several jars, but how big you need depends on how many jars you’re canning. This is to do a water bath, if you don’t have a pressure canner.
- Pressure canner can absolutely be used if you have one!
- Large bowl to make an ice bath for the blanching.
- Side bowl where you can place the peeled skins.
- Tomatoes, of course! Thick, plum tomatoes like San Marzano or Amish Paste are really great for canning and making thicker sauces, but you can use whatever tomato you have.
Beginner’s Guide to Canning Tomatoes
Canning tomatoes is actually super easy and straightforward, it doesn’t require any special techniques and honestly, not much time. There are a few specific details you need to pay attention to, but the process itself isn’t complicated.
Start with Clean Jars
Since canning is all about sterilizing your sauce so it can be stored for months without going bad, it’s crucial that you start with clean jars. The rest of the process is about killing the bacteria in the tomatoes, but all of that is moot if your jars aren’t clean.
If you have a dishwasher, you can put them all in or simply wash by hand. When you start to fill the jars you’ll want them to be warm, so you can either leave them in the dishwasher or if you wash them by hand, place them in simmering water.
Blanching the Tomatoes
This step is all about making it easy to peel the tomato skins off. Blanching is a technique that you can do with any fruit or vegetable and is the first step for many different ways of preserving foods.
In the large pot, put in enough water to cover all your tomatoes and bring to a boil. Once boiling, gently add in your tomatoes. If you have any that are badly damaged or have any signs of mold, don’t use these! But, any tomatoes with small marks can definitely be used.
Some people will make small cuts to make an X on the bottom side, to make the peeling easier. The tomatoes only need to boil until the skin starts to crack, which usually takes only 30 seconds to one minute.
Remember, you’re just boiling to make the skin easier to peel off, not to cook the tomatoes. So, don’t leave them for too long otherwise they’ll become very mushy.
Once the skin cracks, take out the tomato and place in an ice bath in the large bowl. You’ll leave the tomatoes in the ice bath for just a few minutes then they’ll be ready to be peeled.
Peeling the Skins
At first, it may seem tedious to peel the skins off tomatoes, but after the blanching process the skins come off super easily!
Another method for peeling tomatoes is to freeze them. This method is used by gardeners who have indeterminate tomatoes, which means they fruit for several weeks rather than having many ready at once. So, since the tomatoes won’t last at room temperature, gardeners will freeze the tomatoes whole then thaw them when they have enough for a large canning session.
To be clear, if you freeze tomatoes, you don’t need to also blanch them because they’ll be ready to go! Once thawed, the tomato skin comes off super easily just as if they were blanched.
Seriously, all you have to do is peel it off by hand- no knife needed and the skins usually come off in two or three peels! Since it’s the exterior layer, the skin can carry lots of tiny bacteria so taking the skin completely off helps keep everything safe.
You can simply toss the skins in the compost or freeze them to be used whenever needed. You can also dry them which preserves them indefinitely.
If you have a dehydrator, you can use this to dry them or place the skins on a baking sheet and leave in the oven for several hours at the lowest heat. Many people like to blend up the dried skins into a powder to be used for sauces and soups later.
Cut Up Your Tomatoes
Once all the skins are off, you can begin cutting up your tomatoes. The way you cut them completely depends on the texture you want your sauce to be.
Some people dice up the tomatoes into smaller pieces whereas some just cut them into quarters or even just in half. You can even put the tomatoes in whole, which will give you more chunks.
Regardless of what size, you’ll want to remove the part of the tomato that was attached to the stem, because this won’t boil down and is hard to chew on.
Some people remove the tomato core and seeds while others leave it in- this again is up to personal preference. This depends on whether you mind seeds in your tomato sauce. Using just the flesh of the tomato makes a thicker sauce while including the core makes it more liquid.
While you’re cutting your tomatoes, whether they’ve been frozen or blanched, they’ll definitely spill juice everywhere- just be prepared for it and keep going! You can save the juice to use in your sauce or discard it.
Filling the Jars
As I mentioned earlier, you want the jars to be hot when you fill them, this is because they’ll be filled then put into the water bath or pressure canner that’s very hot and could crack if they’re not already warm.
This is where the flexible cutting board is useful- you can pick up the sides of the cutting board and just dump everything into the jars. This is especially helpful if you’re including all the juice from the tomatoes.
No matter what, it’s always super helpful to have a funnel to get all the tomato bits in your jars and not all over the countertop.
If you’re canning with a water bath, it’s important that with each pint of sauce you have, you add in ¼ teaspoon of citric acid. Tomatoes don’t contain enough acid to kill the bacteria nor do water baths heat the tomatoes enough to do this, so you need to add acid to make sure any bacteria in the tomatoes is killed.
You can often find pure citric acid in the baking section of a grocery store or you can use bottled lemon juice concentrate. Fresh lemons vary in their citric acid levels, so using freshly squeezed lemon juice doesn’t always provide the right amount of citric acid.
You want to fill the jars with ½ inch of headspace at the top. If you’re doing a water bath, then you might want to leave a bit more space.
Once the jars are all full, use a butter knife or straight tool and go up and down around the sides of the jar to de-bubble. This just means that you’re going through and releasing any air bubbles that might be in the tomatoes.
Before sealing the jars, you can add on a few leaves of fresh basil as in the traditional Italian recipes. Many gardeners and home canners will add a little bit of basil and then add more fresh basil whenever they actually open the jar and use the sauce.
Since tomato sauce can be used for so many recipes, many people prefer to make their sauce as simple as possible. This way you can make a big batch at once then add in herbs, onions, or garlic depending on what you’re using the sauce for!
When the jars are ready to go, make sure you wipe off the rim of the jar with a clean towel. Any tomato residue can block the lid from sealing properly or can attract bacteria.
Sealing with a Water Bath
Using a water bath is ideal for canning tomatoes for beginners who don’t have a pressure canner. If you’ve never canned before, of course you won’t have a pressure canner but thankfully you don’t need one!
Before putting the tops on the jars, make sure they’re also thoroughly washed. Close the jars but not super tightly, just a quarter turn once they’re on. You want to make sure that they’re securely on, but not completely closed because air needs to be able to leave the jar when cooking.
All you need is a large pot filled with water and bring it to a boil. Place a rack in the water so that the jars aren’t directly touching the bottom of the pot, as this can cause them to crack.
When the water is boiling, use the tongs to gently place the jars into the pot, fitting as many as you can. Do not stack any jars on top of each other.
Boil the jars for at least 40 minutes if they’re pint sized and closer to 45 minutes if you have many or larger jars. If you live at high altitude, remember to consider the different boiling time and adjust as necessary.
Boiling the tomatoes for this long ensures that all the bacteria has been killed so that nothing remains and could develop over the months. Also during the boiling, the tomatoes will soften and get a liquid, sauce texture.
Sealing by Pressure Canner
Of course, if you have or have access to a pressure canner, you should definitely use it! In effect, they both manage the same effect of heating to kill the bacteria and creating pressure to seal the jars.
If you’re using a pressure canner, it’s not necessary to add citric acid to the jars, since the pressure canner is able to reach a high enough heat to surely sanitize the bacteria. However, it doesn’t hurt to add some just as a precaution.
Fill the canner with enough water to cover your jars, but don’t put the jars in yet. You need to let it heat up first, and the right temperature for you will depend on your altitude.
Check the National Center for Home Food Preservation page for canning tomatoes to see what temperature and how long you need for the altitude you’re at.
You need to let the pressure canner vent for 10 minutes- this just means releasing the steam that has built up. Then, gently place your jars in the canner and add the pounds of weight necessary based on your altitude to create pressure.
The jars need to cook for 15 minutes then you can turn the stove top off. Rather than immediately opening it and removing the jars, after you turn off the heat let the pressure canner cool down on its own with the jars in it. This allows the jars to cool a bit instead of directly bringing them out.
Finishing and Double Checking
Once the jars are finished cooking, you’ll need to use the tongs to remove them and place them on a towel, not directly on the countertop.
About 30 minutes after removing them from the water, you should hear each jar pop and that’s how you know it’s completely sealed. This is exactly like when you open something canned and the lid pops, except just the opposite!
When the jars come out of the water, you’ll see that the lids are all rounded on top. The pop happens because the pressure inside the jar pulls the lid down and seals it.
It can take up to 2 hours for the jars to pop, so be patient with them. If you notice some with rounded tops that haven’t popped, this could be a sign that they didn’t seal properly. This could happen if there’s still too much air in the jar and pressure wasn’t created to tightly seal it.
One other way to check if the jars are properly sealed is to remove the ring of the lid and, with the lid still on, pick up the jar. If properly sealed, the lid will stay tight on the jar.
For any jars that you think didn’t seal properly, store in the fridge. They won’t be able to store as long since they’re still exposed, but you can keep it in the fridge for about a week and should use it in this time span.
For all those that are properly sealed, you can leave them out to cool and rest for the next 24 hours. After 24 hours remove the ring of the lid because sometimes the pressure created by the ring will cause the jars to seal, but this is called a “false seal” and won’t actually protect the sauce from rotting.
By removing the lid, you can be sure that all your jars are sealed and no bacteria will be able to enter and develop. Especially for canning tomatoes for beginners, it’s helpful to do all these checks since you may have missed a step and did something slightly off.
Put Your Sauce to Use!
Once you’ve successfully canned your tomatoes, they will store for AT LEAST one year! Following the proper process, they’ll store for about 18 months to 2 years, but most people use all their sauce in this time that they never see the day when it goes bad.
You can open the jars whenever you’re ready to and if you don’t use all the sauce in the jar, put the rest in your fridge as you would with any other canned item. Tomato sauce will last for about 10 days in the fridge.
You can open your canned tomatoes and make sauces for pasta or pizza, use it in soup, or make salsas with it! Whenever you want some fresh tomato flavor in your cooking but don’t have any on hand, crack open one of your jars and put it to use!
From Beginner to Expert Home Canner
It may seem like a lot to learn- I know I felt intimidated for a long time- but canning actually isn’t too complex and generally follows the same process. So, once you gain confidence canning tomatoes, you can begin to can and preserve tons of other veggies and sauces!
You may want to take notes as you begin to learn about the canning process, so that you can keep everything straight. However, those who have been canning for years will tell you that it eventually comes like second nature.
It’s understandably stressful at first, because you want to make sure you do everything correctly and don’t risk spoilage. But be forgiving and know that if some jars don’t seal properly, just use them in the next week and try with another batch of tomatoes.
It’s always better to be safe than sorry with canning and if you have any doubts, play it safe and either keep the jar in the fridge or just toss it in the compost. It’s definitely disappointing to work hard and not get things right, but this is all part of the learning process!
I hope you’re feeling confident after reading all the information provided here and are excited to begin canning! It’s an extremely useful skill and as you advance your gardening abilities, you’ll need to do something with all your produce. Plus, the more comfortable you become with canning, the most you can mix veggies and create your own recipes!
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.