Oh Tomatoes… You tricky, tricky things.
You wouldn’t think home canned tomatoes would be earth-shattering topic, would you?
Well, you’d be surprised.
I’ve seen some pretty heated discussions in regards to how to can tomatoes safely at home. Whenever the conversation comes up in my Homestead & Heritage Cooking Facebook group, there are always members who pull out their tried-and-true recipes from their grandma’s day– because if it worked for her, it should work for me too, right?!
But that’s where it gets tricky.
Many older tomato canning recipes call for using simple water bath canning as the processing method. This is because tomatoes are indeed a fruit and most fruits are perfectly suited to water bath canning due to their high levels of acidity.
However, things change.
Science has learned a thing or two in the past fifty years and it turns out that the canning authorities (like the USDA and the National Center for Home Food Preservation) have realized that tomatoes aren’t always as acidic as grandma originally thought.
Therefore, more modern recommendations call for pressure canners to be using when canning tomatoes. (By the way, this is the pressure canner I use– It may look like an alien space ship, but I love it). Naturally, that causes some confusion from people who have canned tomatoes with their trusty water bath canner for decades.
So when it comes to canning tomatoes, which method is right?
The short answer? Both water bath canning and pressure canning are perfectly acceptable for canning tomatoes safely, BUT no matter which option you choose, you MUST add some sort of acid.
If you are a canning newbie, I just revamped my Canning Made Easy course and it’s ready for YOU! I’ll walk you through each step of the process (safety is my #1 priority!), so you can finally learn to can confidently, without the stress. CLICK HERE to have a look at the course and ALL the bonuses that come with it.
How to Can Tomatoes Safely at Home
Any food with a pH of 4.6 or less can be safely water bath canned.
However, any food with a pH higher than 4.6 must be pressure canned.
Come to find out, tomatoes hover right around 4.6 pH, but they aren’t always consistent, either.
There are hundreds of varieties of tomatoes. In fact, according to the FDA, there are approximately 7,500 varieties of tomatoes. And all these different varieties of tomatoes have varying pH levels, some of which fall well above 4.6.
And while there are some myths floating around claiming it’s only newer strains of tomatoes that are lower in acid, that’s actually not true. There are heirloom varieties that are lower in acid as well. Additionally, some well-meaning folks might tell you that you can tell by the taste of the tomatoes if they’re acidic. Unfortunately, that’s never gonna be legit either. The truth is, many varieties of tomatoes don’t taste acidic simply because they have higher sugar levels that mask the taste.
There are also several conditions that can further reduce the acidity of tomatoes, including:
- Decaying tomatoes
- Over-ripening
- Developing blossom end rot
- Bruising
- Growing tomatoes in the shade
- Ripening off the vine
- And the list goes on…
Basically, there are a whole lot of variables to consider. Why should you care? Well, for one thing, canning tomatoes improperly increases your risk for botulism, which is a HUGE deal. (Learn how to safely can here!). Water bath canning low-acid foods is an invitation for botulism. And when you don’t know the exact acid content, things get sketchy.
Thankfully, there’s a magic weapon so you do NOT have to worry about this!
Good ol’ lemon juice.
That’s it. No matter what one of the 7,500 varieties of tomatoes you happen to be canning. No matter if you want to can them crushed, whole, diced, or as tomato sauce, all you have to do is add some type of acid and you’re all set. It’s that easy. You’re welcome. 😉
Other Acidification Options for Canning Tomatoes Safely
Lemon juice is my favorite acid option for canning tomatoes, but it’s not the only one!
You actually have 3 options when it comes to acids for safely canning tomatoes:
-
Lemon juice (store-bought)
-
Citric acid
-
Vinegar (store-bought)
Lemon Juice
I like to use bottled organic lemon juice, but you can use any bottled option you’d like. However, do not use home-squeezed lemon juice as bottled lemon juice has a known and consistent pH level. Fresh lemons produce lemon juice that has not been tested for acidity, which defeats the purpose of adding it in the first place. Just like the growing conditions for tomatoes that I mentioned above, the lemons’ growing conditions will change their pH levels.
When canning tomatoes, use the following ratios of lemon juice to lower the pH to safe levels for water bath canning:
- 1 tablespoon bottled lemon juice (5% concentration) per pint of tomatoes
- 2 tablespoons bottled lemon juice (5% concentration) per quart of tomatoes
Citric Acid
You can also buy plain citric acid. You can purchase this natural, granulated citric acid and add it to canned tomatoes to raise their acidity level. It’s great to use in recipes where you need a lower pH but you don’t want to add the stronger flavors of vinegar or lemon juice to the finished product.
When canning tomatoes, use the following ratios of citric acid to lower the pH to safe levels for water bath canning:
- ¼ teaspoon citric acid per pint of tomatoes
- ½ teaspoon citric acid per quart of tomatoes
Vinegar
Vinegar is another option, but I don’t recommend it for canned tomatoes. Because, well, you know how vinegar tastes, right? If you do wind up using vinegar for canning tomatoes, select one with at least 5% acidity. Sometimes particular recipes will call for a certain type of vinegar, like apple cider or white. You can safely swap out vinegars, as long as the one you’re swapping in has an acidity level of at least 5%.
When canning tomatoes, use the following ratios of vinegar to lower the pH to safe levels for water bath canning:
- 2 tablespoons vinegar (5% acidity) per pint of tomatoes
- 4 tablespoons vinegar (5% acidity) per quart of tomatoes
Do You Need to Add Acidification for BOTH Water Bath Canning and Pressure Canning?
Whatever type of canning process you decide to use, it is recommended that you add the additional acid in order to can tomatoes safely. Many recipes for pressure canning tomatoes use shorter processing times because the recipes assume that the tomatoes have the correct levels of acid.
You Got This!
I know all this talk of pH levels, 5% acids, and tomato varieties can be confusing at first glance, but don’t let any of it intimidate you! Canned tomatoes should absolutely be a staple in your pantry. All you have to do is remember to add an acid and you’ll be set. Not only is canning tomatoes easy, there’s just nothing like grabbing a jar of summertime from your pantry in the dead of winter.
Looking for a good source for your tomato seeds for next year’s garden? Here are some suggestions, and I recently discovered a great selection of heirloom tomato seeds here as well.
So go ahead. Dice or chop or puree some plump garden freshness. In February, your pasta or soup–and your family–will thank you.
Still nervous about canning? Check out my Canning Guide here!
Want to Know all the Canning Products I Use and Love?
Did you know I have an on-line mercantile of sorts? I link to some of my favorite kitchen tools for food preservation over there. But that barely scratches the surface…
Try my favorite lids for canning, learn more about FOR JARS lids here: http://theprairiehomestead.com/forjars (use code PURPOSE10 for 10% off)
When I first started out canning, I would have loved for someone more experienced to invite me into her kitchen and show me the pans and jars and equipment she used to make all that magic that was stored up in her pantry. I do exactly that and more in my Beginning Canning Course.
More Ways to Preserve Tomatoes:
- How to Freeze Tomatoes
- 40+ Ways to Preserve Tomatoes
- 15 Minute Tomato Sauce Recipe
- How to Make Sun-Dried Tomatoes
- Homemade Pico de Gallo Salsa
Listen to the Old Fashioned On Purpose podcast episode #8 on the topic The Surprising Truth About Canning Tomatoes HERE.
Very innovative work. Great utilization of resources!!
sua dieu hoa hoan kiem http://testsphere.nds-gaming.de/index.php?mod=users&action=view&id=5734
Are the acid ratios per pint/quart whole or once they are processed?
Having read this I thought it was rather informative.
I appreciate you spending some time and effort to put this informative article together.
I once again find myself spending way too much time both
reading and leaving comments. But so what, it was still worthwhile!
Thanks for letting us know! I’m glad you liked this post. 🙂
I use one teaspoon salt and one teaspoon sugar. Would this combination bring up the acid to safely can tomatoes.
No, that wouldn’t bring up the acid. Only adding an acidic ingredient like lemon juice or vinegar would do that.
What’s the skinny on Asboric Acid? Can one use this as an acid to can Tomatoes? Thanks for you thoughts and insight.
So, I just canned a bunch of tomatoes with my grandma yesterday, we used the water bath method, but did not us an acid.
Can I open the jars, add the acid and then put them in the pressure canner to seal them again ?
I need to know this as well. Hate to waste them or get my family sick.
First of all remove the Hoa comment….it could be a virus as I clicked thinking she/he had something further to comment on….it’s the comment with all the question marks.
Secondly, stewing tomatoes, adding lemon juice and flipping the jars is a no no?
Hi! Thanks for all this information! If water bath canning tomatoes, how long must you boil them for? I am finding so many different numbers. Thanks!
This is a great article about canning tomatoes, but if I want to start selling it at the farmers market what should I do about labeling them?
In Oregon in order to sell any home goods from your kitchen your kitchen must be certified. Selling w/o that certification and having someone get bad food could be very costly. It is simple to do, well, kind of simple. Contact your home extension office, they can guide you in getting this done.
I looked up your pressure canner that you use and it says glass top stoves won’t work for it. What else can I use? Does an insta pot heat it enough?
The issue is with the weight and high heat for a sustained period of time. Presto canners weigh less and might work on the glass top stove. Check your stove’s owners manual to see if it allows canners. I use a steam canner instead of water bath as it is now approved and weighs less than a pot filled with water.
Hi Jennifer,
I am replying now incase you haven’t found anything. I am not seeing a reply. I use the Presto 16 quart pressure canner on my glass stove top and have been for several years. Works great, never had a problem.
Hi! Thanks for all this information! If water bath canning tomatoes, how long must you boil them for? I am finding so many different numbers. Thanks!
Yes you can I use a glass top stove I have for year’s just watch the pressure on your canner
When using lemon juice, does it affect the taste of the canned tomatoes?
Please let me know thru email, I want to start canning soon. Thank you so much
Is canning salt plus lemon juice ok
I learned many years ago to add Tomato juice to the jars – I have never had a failure with this method – I add 1/4 cup of tomato juice, 1/2 tsp. sale and 1/2 tsp sugar to each pint. double for quarts. And if i am a bit short of tomatoes or juice to fill the jar, I just add a bit more tomato juice – they or much better than the tomatoes you buy.
Is canning salt plus lemon juice ok
I cook the tomatoes then put them in hot sterile jars with hot sterile sealer lids. They seal and I store them. Am I still threatened with botulism?
Also. Why do some canners store the quart jars upside down?
At what point do you add the lemon juice? During the cooking process or afterwards or does it matter? Thanks for all your information!
If you water bath can, your tomatoes will store for a bit over one year.
If you want to get ahead of the game and only can every 2nd or 3rd year, you should pressure can. I add my lemon juice to the jars and then pour the tomatoes (whole, crushed, sauce, juice) on top. Add salt if desired, wipe, close and pressure can.
I bulk batch something different every year; one year beans, one year tomatoes, one year something else. We’re just now finishing up tomatoes that I canned in 2014; just as clean and tasty as the day they went into the jar.
Yes you can I use a glass top stove I have for year’s just watch the pressure on your canner
I stumbled across this great tip and thought I would share it here. After washing, coring and quartering the tomatoes, spread them out on a wax paper lined sheet pan and and freeze them until rock hard. Then thaw them out in a large bowl. Water from the tomatoes is released into the bowl as they thaw, plus the skins slip right off. Place the tomatoes into a colander as you peel them (I put the colander over a large pot to collect the drips as I peeled, not sure if it will be of any use yet but I didn’t want it to go to waste. I might just use it to wet down my compost pile, 🙂 ). Anyway, this freeze/thaw/drain method saves a ton of time and energy. No need to boil down the tomatoes to reach sauce consistency before canning. Just whiz them in the blender, bring to a boil and can them.
I am so discouraged with my tomatoes. They get little spots that start the rot process before ripening. That doesn’t work with canning tomatoes. My old canning book always stressed using only sound tomatoes. We do eat them raw but not for putting up. Any suggestions?
You might be dealing with Leaf-footed bugs, which suck spots on tomatoes that always go rotten before the rest of the tomato. One way around this is to harvest your tomatoes green or almost completely green and let them ripen indoors (read more here: https://www.theprairiehomestead.com/2014/10/ripen-green-tomatoes.html). Another thing you can do is simply cut off the rotten parts. No biggie. I almost only can with “seconds” tomatoes from the farmer’s market because they are cheap. Simply cut out all the yucky parts and you can continue with your canning adventures.
Thank you Chris. I will check the info link and hope for a solution.
By the way Jill, I am so impressed by all you manage to do 😉
I followed the canned tomatoes, the canned spaghetti sauce, and the marinara recipes exactly and they turned out perfectly.