How to Can Tomatoes

Canning your own fresh produce can sound like a daunting task, but it’s really not as overwhelming as you might think! You start off by just prepping or cooking your produce (something you’ve likely done many times before) and then you go through the extra step of processing (i.e. boiling) the prepared food in glass jars. There are of course some details in-between when it comes to food safety, but as with anything – practice makes perfect! Kiran and I got some practice ourselves recently and are excited to show you how to can tomatoes, step-by-step.

How to can tomatoes on 100 Days of #RealFood

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Safety First

One of the most important things to know about canning is that it’s imperative to use a reliable recipe from a reliable source. There is a whole science behind making sure your canned food does not spoil (or worse, cause a foodborne illness), so unless you are a very experienced canner this is just not an area where you want to experiment.

I personally think of the Ball Blue Book Guide to Preserving as the “bible” of basic canning recipes, but if you want to get more creative there are sites/books like Food in Jars that are great reliable resources as well. Don’t let the safety aspect scare you away  …if you follow the directions and start practicing with high-acid foods (fruits and tomatoes) there’s very little chance anything could go wrong. Let’s remember how many generations before us have been preserving their seasonal foods through canning!

Step-by-Step Instructions

How to can tomatoes on 100 Days of #RealFood
The Ball Blue Book Guide to Preserving

As I mentioned, Kiran and I got together this summer to try our hand at canning tomatoes. I had some experience canning jam before and we’ve both taken canning classes, but the funny thing is even with all that experience we still felt like we had to read the directions 20 million times just to make sure we were not missing a single step. This is how we canned our tomatoes following the Ball Blue Book Guide to Preserving

Prep Work

  1. We went to our local farmers’ market and bought 20 pounds of tomatoes. You want to inspect each one to make sure they’re free of cracks and bad spots.
  2. We then bought a set of quart glass canning jars. It would also be okay to use canning jars you already own, BUT you would need to ensure the jars are free of nicks and cracks and you would need to purchase new (never been used) lids for this project, unless you have the reusable kind. We ended up needing 6 quart jars since a few of our tomatoes spoiled in the 3 days between purchasing them and canning them and had to be trashed.
  3. We also bought lemon juice – this is required and helps increase the acid level of the tomatoes for food safety reasons.

Canning Day

How to can tomatoes on 100 Days of #RealFood
Sterilizing our jars and canning tools
  1. We started by setting out all of our supplies and sterilizing our jars, bands, and canning tools (funnel, lid lifter, tongs, etc.) in the dishwasher. We sterilized the lids separately in hot water (not to exceed 180 degrees F). While you could sterilize everything in pots of water, I think it’s easier to do the bulk of it in the dishwasher, and reliable sources say this is an approved method for everything except the lids.
  2. We filled a large lobster pot I happen to own with water (of course a canning pot would be even better if you have one!), set a wire canning rack inside, and put it on the stove on high to boil. We used this same pot to both prepare our tomatoes and to process our jars.
  3. Next, we prepared our tomatoes. There are different ways to do this, and we chose the “raw pack” method (mainly because it sounded the easiest – ha!). So next we dropped our tomatoes (in batches) into the boiling water and blanched them for about 1 minute. The purpose of this step is to make it easier to get the skins off. Once we were done blanching we set up an assembly line of sorts. Kiran took the peels off then passed them to me to cut out and discard the top of the core. At this point you can leave the tomatoes whole or cut them in quarters. We left them whole because again – it was the easiest way to go!
  4. By then the dishwasher was done so we set up our clean jars on a clean dish towel and dropped in the 2 tablespoons of lemon juice required for each quart jar (it’s 1 tablespoon per pint jar). Then we added as many tomatoes that would fit into each jar, topped them off with water until only 1/2″ of headspace was left (it’s important to follow this measurement guideline), and added a teaspoon of salt to each jar.
  5. Once all the jars were filled we slid a nonmetallic spatula all around on the inside edges of the jars to break up any air bubbles and then added more water if necessary. We honestly didn’t need much water at all because our tomatoes were so juicy!
  6. Lastly, we wiped the rims and jars with a clean towel, carefully placed the sterilized lids on the jars (not touching the underside by using 0ur magnetic lid tool), loosely screwed on the bands, and then lowered as many jars as would fit into the large pot of boiling water. We ensured the water covered the jars completely, let it come back up to a light boil, and started the timer for 45 minutes.
  7. When we were done we carefully used our jar tongs to get the hot jars out of the pot and let them rest on the counter for a while before handling. Little by little the lids started to pop to let us know they were sealed – here is a pic of our finished product!
How to can tomatoes on 100 Days of #RealFood
The finished product!

Questions We Had

Now even though we were using some very reliable instructions, we found ourselves with quite a few questions along the way. So I called up Ball on the phone (they’re there to answer any of your canning questions for free! 1-800-240-3340) and found out the following…

  • Lemon juice: Does it have to be bottled (not fresh)?
    Apparently you can use fresh! We did not know that and went with bottled just to be safe because a few recipes we saw specifically said “bottled.” Now we know!
  • Tomatoes: Can you only process whole (or chopped) tomatoes or how about spaghetti sauce?
    Processing sauce is possible, but requires a different procedure and lemon juice as well, which you might not normally add to sauce. I personally like having plain whole tomatoes on hand because they are more versatile – you could use them to make sauce or soup or anything your heart desires!
  • End product: Why are my tomatoes floating in the jars?
    This happened to us and we learned it is not ideal, but it’s okay. This is a common (and completely safe) issue and can happen when tomatoes are overripe or not all the air bubbles were removed when packing the jars.
  • Packing tomatoes into jars: Can we use our hands or is a (wooden) spoon better?
    Clean hands or clean wooden spoon are both okay, but a non-metallic spoon will be more sterilized than your fingers/fingernails.
  • Sterilization: Do you have to boil the jars or is the dishwasher okay for sterilization?
    Ball has not tested the dishwasher (so they can’t give it their blessing), but other reliable sources say it’s okay. As I mentioned above the lids should not go in the dishwasher and instead be sterilized in a pot of water not to exceed 180 degrees F).
  • Processing time: Is it possible to “over-process” i.e. boil for too long?
    Over-processing will possibly diminish the quality of the product, but won’t affect the safety of the food.

Well, overall our canning day was a success! Kiran and I would love to hear your canning tips in the comments …we can’t wait to get together to process our next batch.

How to can tomatoes on 100 Days of #RealFood

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26 thoughts on “How to Can Tomatoes”

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  1. Love the concepts and tips from 100 days of real food. However the link to the strawberry jam w/o pectin didn’t include an actual recipe with measurements. Simply an overview. The same issue with slow cooker ketchup a link but no recipe. Very frustrating!

    1. I’ve found the recipe using my laptop ,but not when using the mobile app. Just glad to find a jam w/o pectin is available

    1. Lindy, it’s showing you that you can eat locally all year by buying your tomatoes from a farms market near you then canning them to enjoy throughout the year. Love this blog!! I’ll have to try this with the tomatoes that are growing in my garden!!!

  2. You should add a beauty blog! “How to Not Look Like A Hot Mess In A Hot Kitchen” lol. You both look so cool and beautiful!
    I love this site. Thank you for showing me how easy it is to cut the garbage out of our diet!

  3. I learned how to can from my aunt a couple years ago (but also use Ball’s canning book). I soak my tomatoes in a vinegar water bath before blanching them to make sure they are super clean. Depending on the tomato variety (specifically the acidity), I add a little vinegar to the jar as an added precaution. And then make sure to eat them within a year of canning (not that they will last that long). You can never be too safe canning… but it’s definitely worth all of the work when you pop open a jar and you smell summer again while it’s snowing outside! :)

  4. There’s one important final point you should make: as with any home-canned good, don’t store the jars with the screw tops on.

    This way, if you go to get a jar 6 months later and the top comes off without effort, you know not to eat the food. If you store with the screw-top band in place, it’s impossible to know whether the seal was broken from the beginning or whether it happened when you unscrewed it (which can happen).

    Once the jars cool (overnight, usually), remove the screw bands and gently check the seal on all the jars, then store them that way.

    If any didn’t seal, the lid will come right off. It’s OK to eat the food but it will have a normal, limited shelf life. It’s better to know now and not waste the food! Plus you get to check the seal again when using the canned food.

    1. Erik – I’ve been canning for years. I learned from my mother-n-law and her mother. We have always left the rings on our jars, and have never had a problem. You just have to make sure you don’t screw them on too tight or overfill the jars. That’s where you come across the problem of the jar not sealing properly. To each his own though :)

  5. I’m really wanting to start canning but I’ve read canning on a glass top stove (with flat eyes) is not advised. Did you use one or the raised, older stove?

    1. You can use a flat top stove! You just need to make sure that your canning pot (I use a large soup pot) has a flat bottom and fits the diameter of your burner. The website has a lot of good ideas for alternative canning pots, I use a silicone trivet in the bottom & got the idea from there. You can even pressure can on a flat top if you have a canner that has a smaller, flat bottom that fits your burner.

  6. Loved the post! Thank you for taking us step by step, because although I’ve always wanted to get into canning I have been too scared to try it. What types of sauces and soups and other things are you planning to make?

    1. Kiran Dodeja Smith

      Hi Nicole,
      I was also scared to try it, but it really is not bad!! I’m looking forward to using my tomatoes for homemade sauce when tomatoes are not in season. Give it a shot!

  7. So, how “loosly” do you screw the lids on? And then are you saying that you don’t tighten them after removing from the boiling water?

    1. You want the bands “tight” enough just to keep the lids in place during processing – after they are boiled the bands aren’t even necessary because the lids are sealed down onto the jar. I hope that helps!

  8. I love this post! This year will be my third year canning tomatoes… It is super easy as long as you follow a recipe. The canned (jar) tomatoes taste so much better than the store-bought canned tomatoes and I feel better knowing my family is not eating leached BPAs from the can lining.

  9. Am I the only one who loves your kitchen so much that I never see anything else in the photo but that awesome brick backsplash! Thanks for this post, been wanting to can tomatoes!

    1. Haha – that’s so sweet. Too bad we are moving out of this house this weekend! I’m super excited about our new kitchen though :)